Add thymeleaf-htmx module: Spring Boot 4.1.2 + Thymeleaf 3.1.5 + htmx 2.0.11 CRUD UI with fragment rendering, 422 validation re-render, pagination, inline edit, delete, MockMvc tests and a Chromium check

Co-Authored-By: Claude Sonnet 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_017ic4b7rnC7jppGGdHGESvy

README.md

@@ -9,6 +9,7 @@ files.
 
 | Directory | Article | What it demonstrates |
 |---|---|---|
+| [`thymeleaf-htmx/`](thymeleaf-htmx) | [Spring Boot 4 + Thymeleaf + htmx: Server-Side CRUD UI in 2026](https://ankurm.com/spring-boot-thymeleaf-htmx-crud-ui/) | one URL answering as full page or fragment on `HX-Request`, a Thymeleaf layout, 422 validation re-render, pagination, inline edit and delete, 10 MockMvc tests plus a headless-Chromium check that observed htmx 2 ignoring a 204 and (without a config tag) a 422 |
 | [`sbom/`](sbom) | [Spring Boot SBOM in Practice: the tools jar-mode sbom Command, CycloneDX and Dependency Scanning](https://ankurm.com/spring-boot-sbom-tools-jarmode-cyclonedx-dependency-scanning/) | the 4.2.0-RC1 `java -Djarmode=tools -jar app.jar sbom` command (absent in 4.1.2), the CycloneDX document the build puts in the jar, `/actuator/sbom`, an SBOM that lists 8 starters not in the jar and misses the jar mode's own library, a licence rule that wrongly flags dual-licensed logback, and an OSV scan that finds Log4Shell in a deliberately old build |
 | [`hexagonal/`](hexagonal) | [Hexagonal Architecture (Ports and Adapters) in Spring Boot 4](https://ankurm.com/hexagonal-architecture-ports-and-adapters-spring-boot-4/) | a 4-module Maven reactor that makes "the core has no Spring dependency" something `mvn dependency:tree` proves rather than a naming convention, testing the core with zero Spring context, and a Spring Boot 4 test-slice-artifact split (`@DataJpaTest`, `@WebMvcTest`, `TestRestTemplate`) hit and fixed along the way |
 | [`actuator-in-production/`](actuator-in-production) | [Spring Boot Actuator in Production](https://ankurm.com/spring-boot-actuator-production-endpoints-security-health-indicators/) | endpoint exposure defaults, securing Actuator, custom health indicators and how they hang |

thymeleaf-htmx/.gitignore

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+target/
+browser-check/node_modules/
+browser-check/package-lock.json

thymeleaf-htmx/README.md

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+# thymeleaf-htmx
+
+Companion project for **Spring Boot 4 + Thymeleaf + htmx: Server-Side CRUD UI in 2026** on **[ankurm.com](https://ankurm.com)**.
+
+A contacts list with search, pagination, create-with-validation, inline edit and delete. All HTML is rendered by Thymeleaf; htmx only decides *which part* of a page to replace. About 25 lines of JavaScript-free attributes, no JS framework, no build step.
+
+Every console block in the article is quoted from `output/`. The MockMvc transcripts are written by the tests themselves (they assert on the same data), and `output/11-browser-check.txt` comes from headless Chromium driving the packaged jar.
+
+## Versions
+
+| | |
+|---|---|
+| Spring Boot | 4.1.2 (latest GA on Maven Central; 4.2.0-RC1 exists but is not GA) |
+| Thymeleaf | 3.1.5.RELEASE (managed by Boot) |
+| htmx | 2.0.11 as the WebJar `org.webjars.npm:htmx.org` (htmx 4.0.0 exists on npm `next`; see the article) |
+| JDK | 25 |
+| Test tooling | `spring-boot-starter-webmvc-test`, `spring-boot-starter-thymeleaf-test`; Playwright 1.64.1 for the browser check (optional) |
+
+## Run
+
+```bash
+export JAVA_HOME=/path/to/jdk-25
+mvn spring-boot:run          # http://localhost:8080/contacts
+mvn test                     # 10 MockMvc tests, rewrite output/01..09
+./scripts/run-all.sh         # tests + live curl + browser check, regenerates all of output/
+```
+
+The browser check needs Node 20+ and a one-time `npx playwright install chromium`.
+
+## Where things are
+
+| Concern | File |
+|---|---|
+| Layout fragment (`layout(title, content)`), htmx config meta tag, WebJar script tag | `templates/layout/base.html` |
+| List page + the `table` fragment htmx receives | `templates/contacts/list.html` |
+| Row, edit-row (also the error state) | `templates/contacts/fragments.html` |
+| Create form (full page and `form` fragment) | `templates/contacts/new.html` |
+| Fragment vs full page decision (`HX-Request`, `HX-History-Restore-Request`) | `Htmx.java`, `ContactController.java` |
+| `Vary` header | `VaryHtmxFilter.java` |
+| Contract tests | `ContactUiTest.java`, `Transcript.java` |
+| Real-browser behaviour checks | `browser-check/check.mjs` |
+
+## Output
+
+| File | Shows |
+|---|---|
+| `output/00-mvn-test.txt` | surefire summary |
+| `output/01-full-page-vs-fragment.txt` | same URL, with and without `HX-Request` |
+| `output/02-history-restore-gets-full-page.txt` | the history-miss case |
+| `output/03-htmx-webjar.txt` | version-less WebJar path resolved to the pinned version |
+| `output/04-pagination-and-search.txt` | last page, page past the end, search |
+| `output/05-create-validation-errors.txt` | 422 with errors, fragment and full page |
+| `output/06-create-success.txt` | `HX-Redirect` vs 302 |
+| `output/07-inline-edit.txt` | edit row, failed save, successful save |
+| `output/08-delete.txt` | 200 + `HX-Trigger`, 404 |
+| `output/09-delete-last-page-clamps.txt` | pager after deleting the last page's rows |
+| `output/10-live-curl.txt` | real Tomcat answering with curl |
+| `output/11-browser-check.txt` | Chromium: swaps, history, 204 and 422 traps |
+
+Not covered: Spring Security / CSRF (no Security dependency in this module), file uploads, and htmx 4.

thymeleaf-htmx/browser-check/check.mjs

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+// Drives the running app in headless Chromium so the htmx behaviour claims are observed, not assumed.
+// usage: node check.mjs http://localhost:18083
+import { chromium } from 'playwright';
+
+const base = process.argv[2] ?? 'http://localhost:18083';
+const out = [];
+const log = (s) => { out.push(s); console.log(s); };
+const rows = (page) => page.locator('#contact-table tbody tr[id]');
+const names = async (page) => (await rows(page).locator('td:first-child').allTextContents()).map(s => s.trim());
+
+const browser = await chromium.launch();
+const ctx = await browser.newContext();
+const page = await ctx.newPage();
+const requests = [];
+page.on('request', r => { if (r.url().startsWith(base) && !r.url().includes('/webjars/') && !r.url().endsWith('.css'))
+  requests.push(`${r.method()} ${r.url().replace(base, '')}  HX-Request=${r.headers()['hx-request'] ?? '-'} HX-History-Restore-Request=${r.headers()['hx-history-restore-request'] ?? '-'}`); });
+
+log('== 1. load, then search without a page reload');
+await page.goto(base + '/contacts');
+await page.evaluate(() => { window.__marker = 'same-document'; });
+log('htmx loaded: ' + await page.evaluate(() => typeof htmx + ' ' + htmx.version));
+log('rows on first page: ' + (await rows(page).count()));
+await page.fill('input[name=q]', 'kamat');
+await page.waitForFunction(() => document.querySelectorAll('#contact-table tbody tr[id]').length === 1);
+log('after typing "kamat": ' + JSON.stringify(await names(page)));
+log('address bar: ' + page.url().replace(base, ''));
+log('elements with id contact-table: ' + await page.locator('#contact-table').count());
+log('document survived (no reload): ' + (await page.evaluate(() => window.__marker)));
+
+log('\n== 2. pagination + back button');
+await page.fill('input[name=q]', '');
+await page.waitForFunction(() => document.querySelector('.pager span')?.textContent.includes('23 contacts'));
+// no history snapshots: Back is a cache miss, so htmx must ask the server for the whole page
+await page.evaluate(() => { htmx.config.historyCacheSize = 0; localStorage.removeItem('htmx-history-cache'); });
+await page.click('text=Next');
+await page.waitForFunction(() => document.querySelector('.pager span')?.textContent.startsWith('Page 2'));
+log('page 2 names: ' + JSON.stringify(await names(page)));
+log('address bar: ' + page.url().replace(base, ''));
+const mark = requests.length;
+await page.goBack();
+await page.waitForFunction(() => document.querySelector('.pager span')?.textContent.startsWith('Page 1'));
+log('Back request: ' + requests.slice(mark).join(' | '));
+log('after Back: h1=' + JSON.stringify(await page.locator('h1').textContent()) + ', pager=' + JSON.stringify(await page.locator('.pager span').textContent()));
+
+log('\n== 3. inline edit with a validation error');
+const first = rows(page).first();
+await first.locator('text=Edit').click();
+await page.waitForSelector('tr.editing');
+await page.fill('tr.editing input[name=name]', '');
+await page.fill('tr.editing input[name=email]', 'nope');
+await page.click('tr.editing >> text=Save');
+await page.waitForSelector('tr.editing small.error');
+log('row still editing, errors: ' + JSON.stringify(await page.locator('tr.editing small.error').allTextContents()));
+await page.fill('tr.editing input[name=name]', 'Aarav K.');
+await page.fill('tr.editing input[name=email]', '[email protected]');
+await page.click('tr.editing >> text=Save');
+await page.waitForSelector('tr:not(.editing) td:text-is("Aarav K.")');
+log('saved, row is read-only again: ' + JSON.stringify(await names(page)));
+
+log('\n== 4. delete with confirm');
+const beforeDelete = requests.length;
+page.once('dialog', d => { log('confirm dialog: ' + JSON.stringify(d.message())); d.accept(); });
+await rows(page).first().locator('text=Delete').click();
+await page.waitForFunction(() => document.querySelector('.pager span')?.textContent.includes('22 contacts'));
+log('pager after delete: ' + JSON.stringify(await page.locator('.pager span').textContent()));
+await page.waitForTimeout(500);
+log('requests caused by one delete: ' + JSON.stringify(requests.slice(beforeDelete)));
+
+log('\n== 5. create form: 422 re-render, then success');
+await page.goto(base + '/contacts/new');
+await page.fill('input[name=name]', '');
+await page.fill('input[name=email]', 'x');
+await page.fill('input[name=role]', 'Tester');
+await page.click('button[type=submit]');
+await page.waitForSelector('small.error');
+log('errors shown in place: ' + JSON.stringify(await page.locator('small.error').allTextContents()));
+log('still on: ' + page.url().replace(base, '') + ', typed email kept: ' + await page.inputValue('input[name=email]'));
+await page.fill('input[name=name]', 'Zoya Khan');
+await page.fill('input[name=email]', '[email protected]');
+await page.click('button[type=submit]');
+await page.waitForURL(base + '/contacts');
+log('HX-Redirect landed on: ' + page.url().replace(base, ''));
+
+log('\n== 6. the two status-code traps, observed');
+// (a) a 204 answer to DELETE: htmx 2 does not swap it, the row stays
+await page.route('**/contacts/*', async route => {
+  if (route.request().method() === 'DELETE') return route.fulfill({ status: 204 });
+  return route.continue();
+});
+const before = await rows(page).count();
+page.once('dialog', d => d.accept());
+await rows(page).first().locator('text=Delete').click();
+await page.waitForTimeout(800);
+log(`DELETE answered 204: rows before=${before}, after=${await rows(page).count()} (row not removed)`);
+await page.unroute('**/contacts/*');
+
+// (b) the same 422 without the htmx-config meta tag
+await page.route('**/contacts/*/edit', route => route.continue());
+await page.route('**/contacts', async route => {
+  if (route.request().method() !== 'GET' || route.request().headers()['hx-request']) return route.continue();
+  const resp = await route.fetch();
+  const html = (await resp.text()).replace(/<meta name="htmx-config"[\s\S]*?>/, '');
+  return route.fulfill({ response: resp, body: html });
+});
+await page.goto(base + '/contacts');
+log('htmx-config meta present: ' + (await page.locator('meta[name=htmx-config]').count()));
+await rows(page).first().locator('text=Edit').click();
+await page.waitForSelector('tr.editing');
+await page.fill('tr.editing input[name=name]', '');
+await page.click('tr.editing >> text=Save');
+await page.waitForTimeout(800);
+log('Save answered 422 without the meta tag: errors visible = ' + (await page.locator('tr.editing small.error').count()));
+
+log('\n== requests the browser made (excluding static files)');
+for (const r of requests) log(r);
+await browser.close();

thymeleaf-htmx/browser-check/package.json

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+{ "name": "thymeleaf-htmx-browser-check", "private": true, "type": "module",
+  "dependencies": { "playwright": "1.64.1" } }

thymeleaf-htmx/output/00-mvn-test.txt

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+Tests run: 10, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 11.50 s -- in com.ankurm.thymeleafhtmx.ContactUiTest

thymeleaf-htmx/output/01-full-page-vs-fragment.txt

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+# request (curl notation, sent through MockMvc): curl /contacts
+HTTP 200
+Vary: HX-Request
+Vary: HX-History-Restore-Request
+---- body (3831 chars) ----
+<!DOCTYPE html>
+<html lang="en">
+<head>
+  <meta charset="utf-8">
+  <meta name="viewport" content="width=device-width, initial-scale=1">
+  <title>Contacts</title>
+  <!-- htmx 2 swaps 2xx/3xx only. 422 must be allowed to swap, or validation errors never appear. -->
+  <meta name="htmx-config"
+        content='{"responseHandling":[{"code":"204","swap":false},{"code":"[23]..","swap":true},{"code":"422","swap":true,"error":false},{"code":"[45]..","swap":false,"error":true},{"code":"...","swap":false}]}'>
+  <link rel="stylesheet" href="/css/app.css">
+  <script src="/webjars/htmx.org/2.0.11/dist/htmx.min.js" defer></script>
+</head>
+<body>
+  <header><a href="/contacts">Contacts</a></header>
+  <main>
+  <h1>Contacts</h1>
+
+  <p><a href="/contacts/new">New contact</a></p>
+
+  <form action="/contacts" method="get" role="search">
+    <input type="search" name="q" value="" placeholder="Search name or email"
+           hx-get="/contacts" hx-trigger="input changed delay:300ms, search"
+           hx-target="#contact-table" hx-swap="outerHTML" hx-push-url="true">
+    <noscript><button type="submit">Search</button></noscript>
+  </form>
+
+  <!-- th:fragment "table" is exactly what an htmx request gets back -->
+  <div id="contact-table" hx-trigger="contactsChanged from:body" hx-target="this" hx-swap="outerHTML" hx-get="/contacts?page=0">
+    <table>
+      <thead><tr><th>Name</th><th>Email</th><th>Role</th><th></th></tr></thead>
+      <tbody>
+        
+          <tr id="contact-1">
+  <td>Aarav Kulkarni</td>
+  <td>[email protected]</td>
+  <td>Developer</td>
+  <td>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-get="/contacts/1/edit">Edit</button>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-delete="/contacts/1" hx-confirm="Delete Aarav Kulkarni?">Delete</button>
+  </td>
+</tr>
+        
+          <tr id="contact-2">
+  <td>Bhavna Joshi</td>
+  <td>[email protected]</td>
+  <td>Tester</td>
+  <td>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-get="/contacts/2/edit">Edit</button>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-delete="/contacts/2" hx-confirm="Delete Bhavna Joshi?">Delete</button>
+  </td>
+</tr>
+        
+          <tr id="contact-3">
+  <td>Chinmay Desai</td>
+  <td>[email protected]</td>
+  <td>Architect</td>
+  <td>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-get="/contacts/3/edit">Edit</button>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-delete="/contacts/3" hx-confirm="Delete Chinmay Desai?">Delete</button>
+  </td>
+</tr>
+        
+          <tr id="contact-4">
+  <td>Divya Nair</td>
+  <td>[email protected]</td>
+  <td>Manager</td>
+  <td>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-get="/contacts/4/edit">Edit</button>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-delete="/contacts/4" hx-confirm="Delete Divya Nair?">Delete</button>
+  </td>
+</tr>
+        
+          <tr id="contact-5">
+  <td>Eshaan Patil</td>
+  <td>[email protected]</td>
+  <td>Developer</td>
+  <td>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-get="/contacts/5/edit">Edit</button>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-delete="/contacts/5" hx-confirm="Delete Eshaan Patil?">Delete</button>
+  </td>
+</tr>
+        
+        
+      </tbody>
+    </table>
+    <nav class="pager" aria-label="Pages">
+      
+      <span>Page 1 of 5 (23 contacts)</span>
+      <a href="/contacts?page=1" hx-target="#contact-table" hx-push-url="true" hx-get="/contacts?page=1">Next &raquo;</a>
+    </nav>
+  </div>
+</main>
+</body>
+</html>
+
+# request (curl notation, sent through MockMvc): curl -H 'HX-Request: true' /contacts
+HTTP 200
+Vary: HX-Request
+Vary: HX-History-Restore-Request
+---- body (2598 chars) ----
+<div id="contact-table" hx-trigger="contactsChanged from:body" hx-target="this" hx-swap="outerHTML" hx-get="/contacts?page=0">
+    <table>
+      <thead><tr><th>Name</th><th>Email</th><th>Role</th><th></th></tr></thead>
+      <tbody>
+        
+          <tr id="contact-1">
+  <td>Aarav Kulkarni</td>
+  <td>[email protected]</td>
+  <td>Developer</td>
+  <td>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-get="/contacts/1/edit">Edit</button>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-delete="/contacts/1" hx-confirm="Delete Aarav Kulkarni?">Delete</button>
+  </td>
+</tr>
+        
+          <tr id="contact-2">
+  <td>Bhavna Joshi</td>
+  <td>[email protected]</td>
+  <td>Tester</td>
+  <td>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-get="/contacts/2/edit">Edit</button>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-delete="/contacts/2" hx-confirm="Delete Bhavna Joshi?">Delete</button>
+  </td>
+</tr>
+        
+          <tr id="contact-3">
+  <td>Chinmay Desai</td>
+  <td>[email protected]</td>
+  <td>Architect</td>
+  <td>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-get="/contacts/3/edit">Edit</button>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-delete="/contacts/3" hx-confirm="Delete Chinmay Desai?">Delete</button>
+  </td>
+</tr>
+        
+          <tr id="contact-4">
+  <td>Divya Nair</td>
+  <td>[email protected]</td>
+  <td>Manager</td>
+  <td>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-get="/contacts/4/edit">Edit</button>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-delete="/contacts/4" hx-confirm="Delete Divya Nair?">Delete</button>
+  </td>
+</tr>
+        
+          <tr id="contact-5">
+  <td>Eshaan Patil</td>
+  <td>[email protected]</td>
+  <td>Developer</td>
+  <td>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-get="/contacts/5/edit">Edit</button>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-delete="/contacts/5" hx-confirm="Delete Eshaan Patil?">Delete</button>
+  </td>
+</tr>
+        
+        
+      </tbody>
+    </table>
+    <nav class="pager" aria-label="Pages">
+      
+      <span>Page 1 of 5 (23 contacts)</span>
+      <a href="/contacts?page=1" hx-target="#contact-table" hx-push-url="true" hx-get="/contacts?page=1">Next &raquo;</a>
+    </nav>
+  </div>
+

thymeleaf-htmx/output/02-history-restore-gets-full-page.txt

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+# htmx sends BOTH headers when the history cache misses; it swaps the reply into <body>
+# request (curl notation, sent through MockMvc): curl -H 'HX-Request: true' -H 'HX-History-Restore-Request: true' '/contacts?page=1'
+HTTP 200
+Vary: HX-Request
+Vary: HX-History-Restore-Request
+---- body (3937 chars) ----
+<!DOCTYPE html>
+<html lang="en">
+<head>
+  <meta charset="utf-8">
+  <meta name="viewport" content="width=device-width, initial-scale=1">
+  <title>Contacts</title>
+  <!-- htmx 2 swaps 2xx/3xx only. 422 must be allowed to swap, or validation errors never appear. -->
+  <meta name="htmx-config"
+        content='{"responseHandling":[{"code":"204","swap":false},{"code":"[23]..","swap":true},{"code":"422","swap":true,"error":false},{"code":"[45]..","swap":false,"error":true},{"code":"...","swap":false}]}'>
+  <link rel="stylesheet" href="/css/app.css">
+  <script src="/webjars/htmx.org/2.0.11/dist/htmx.min.js" defer></script>
+</head>
+<body>
+  <header><a href="/contacts">Contacts</a></header>
+  <main>
+  <h1>Contacts</h1>
+
+  <p><a href="/contacts/new">New contact</a></p>
+
+  <form action="/contacts" method="get" role="search">
+    <input type="search" name="q" value="" placeholder="Search name or email"
+           hx-get="/contacts" hx-trigger="input changed delay:300ms, search"
+           hx-target="#contact-table" hx-swap="outerHTML" hx-push-url="true">
+    <noscript><button type="submit">Search</button></noscript>
+  </form>
+
+  <!-- th:fragment "table" is exactly what an htmx request gets back -->
+  <div id="contact-table" hx-trigger="contactsChanged from:body" hx-target="this" hx-swap="outerHTML" hx-get="/contacts?page=1">
+    <table>
+      <thead><tr><th>Name</th><th>Email</th><th>Role</th><th></th></tr></thead>
+      <tbody>
+        
+          <tr id="contact-6">
+  <td>Farah Sheikh</td>
+  <td>[email protected]</td>
+  <td>Tester</td>
+  <td>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-get="/contacts/6/edit">Edit</button>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-delete="/contacts/6" hx-confirm="Delete Farah Sheikh?">Delete</button>
+  </td>
+</tr>
+        
+          <tr id="contact-7">
+  <td>Gauri Deshpande</td>
+  <td>[email protected]</td>
+  <td>Architect</td>
+  <td>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-get="/contacts/7/edit">Edit</button>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-delete="/contacts/7" hx-confirm="Delete Gauri Deshpande?">Delete</button>
+  </td>
+</tr>
+        
+          <tr id="contact-8">
+  <td>Harsh Mehta</td>
+  <td>[email protected]</td>
+  <td>Manager</td>
+  <td>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-get="/contacts/8/edit">Edit</button>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-delete="/contacts/8" hx-confirm="Delete Harsh Mehta?">Delete</button>
+  </td>
+</tr>
+        
+          <tr id="contact-9">
+  <td>Isha Rao</td>
+  <td>[email protected]</td>
+  <td>Developer</td>
+  <td>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-get="/contacts/9/edit">Edit</button>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-delete="/contacts/9" hx-confirm="Delete Isha Rao?">Delete</button>
+  </td>
+</tr>
+        
+          <tr id="contact-10">
+  <td>Jayesh Pawar</td>
+  <td>[email protected]</td>
+  <td>Tester</td>
+  <td>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-get="/contacts/10/edit">Edit</button>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-delete="/contacts/10" hx-confirm="Delete Jayesh Pawar?">Delete</button>
+  </td>
+</tr>
+        
+        
+      </tbody>
+    </table>
+    <nav class="pager" aria-label="Pages">
+      <a href="/contacts?page=0" hx-target="#contact-table" hx-push-url="true" hx-get="/contacts?page=0">&laquo; Prev</a>
+      <span>Page 2 of 5 (23 contacts)</span>
+      <a href="/contacts?page=2" hx-target="#contact-table" hx-push-url="true" hx-get="/contacts?page=2">Next &raquo;</a>
+    </nav>
+  </div>
+</main>
+</body>
+</html>
+

thymeleaf-htmx/output/03-htmx-webjar.txt

@@ -0,0 +1,3 @@
+# script tag as rendered (the template asks for /webjars/htmx.org/dist/htmx.min.js, no version)
+# <script src="/webjars/htmx.org/2.0.11/dist/htmx.min.js" defer></script>
+# GET /webjars/htmx.org/2.0.11/dist/htmx.min.js -> 200, 52182 bytes, Content-Type text/javascript

thymeleaf-htmx/output/04-pagination-and-search.txt

@@ -0,0 +1,138 @@
+# request (curl notation, sent through MockMvc): curl -H 'HX-Request: true' '/contacts?page=4'
+HTTP 200
+---- body (1763 chars) ----
+<div id="contact-table" hx-trigger="contactsChanged from:body" hx-target="this" hx-swap="outerHTML" hx-get="/contacts?page=4">
+    <table>
+      <thead><tr><th>Name</th><th>Email</th><th>Role</th><th></th></tr></thead>
+      <tbody>
+        
+          <tr id="contact-21">
+  <td>Uma Pillai</td>
+  <td>[email protected]</td>
+  <td>Developer</td>
+  <td>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-get="/contacts/21/edit">Edit</button>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-delete="/contacts/21" hx-confirm="Delete Uma Pillai?">Delete</button>
+  </td>
+</tr>
+        
+          <tr id="contact-22">
+  <td>Vikram Singh</td>
+  <td>[email protected]</td>
+  <td>Tester</td>
+  <td>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-get="/contacts/22/edit">Edit</button>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-delete="/contacts/22" hx-confirm="Delete Vikram Singh?">Delete</button>
+  </td>
+</tr>
+        
+          <tr id="contact-23">
+  <td>Yash Thakur</td>
+  <td>[email protected]</td>
+  <td>Architect</td>
+  <td>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-get="/contacts/23/edit">Edit</button>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-delete="/contacts/23" hx-confirm="Delete Yash Thakur?">Delete</button>
+  </td>
+</tr>
+        
+        
+      </tbody>
+    </table>
+    <nav class="pager" aria-label="Pages">
+      <a href="/contacts?page=3" hx-target="#contact-table" hx-push-url="true" hx-get="/contacts?page=3">&laquo; Prev</a>
+      <span>Page 5 of 5 (23 contacts)</span>
+      
+    </nav>
+  </div>
+
+# request (curl notation, sent through MockMvc): curl -H 'HX-Request: true' '/contacts?page=99'
+HTTP 200
+---- body (1763 chars) ----
+<div id="contact-table" hx-trigger="contactsChanged from:body" hx-target="this" hx-swap="outerHTML" hx-get="/contacts?page=4">
+    <table>
+      <thead><tr><th>Name</th><th>Email</th><th>Role</th><th></th></tr></thead>
+      <tbody>
+        
+          <tr id="contact-21">
+  <td>Uma Pillai</td>
+  <td>[email protected]</td>
+  <td>Developer</td>
+  <td>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-get="/contacts/21/edit">Edit</button>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-delete="/contacts/21" hx-confirm="Delete Uma Pillai?">Delete</button>
+  </td>
+</tr>
+        
+          <tr id="contact-22">
+  <td>Vikram Singh</td>
+  <td>[email protected]</td>
+  <td>Tester</td>
+  <td>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-get="/contacts/22/edit">Edit</button>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-delete="/contacts/22" hx-confirm="Delete Vikram Singh?">Delete</button>
+  </td>
+</tr>
+        
+          <tr id="contact-23">
+  <td>Yash Thakur</td>
+  <td>[email protected]</td>
+  <td>Architect</td>
+  <td>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-get="/contacts/23/edit">Edit</button>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-delete="/contacts/23" hx-confirm="Delete Yash Thakur?">Delete</button>
+  </td>
+</tr>
+        
+        
+      </tbody>
+    </table>
+    <nav class="pager" aria-label="Pages">
+      <a href="/contacts?page=3" hx-target="#contact-table" hx-push-url="true" hx-get="/contacts?page=3">&laquo; Prev</a>
+      <span>Page 5 of 5 (23 contacts)</span>
+      
+    </nav>
+  </div>
+
+# request (curl notation, sent through MockMvc): curl -H 'HX-Request: true' '/contacts?q=KAMAT'
+HTTP 200
+---- body (828 chars) ----
+<div id="contact-table" hx-trigger="contactsChanged from:body" hx-target="this" hx-swap="outerHTML" hx-get="/contacts?q=KAMAT&amp;page=0">
+    <table>
+      <thead><tr><th>Name</th><th>Email</th><th>Role</th><th></th></tr></thead>
+      <tbody>
+        
+          <tr id="contact-19">
+  <td>Sneha Kamat</td>
+  <td>[email protected]</td>
+  <td>Architect</td>
+  <td>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-get="/contacts/19/edit">Edit</button>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-delete="/contacts/19" hx-confirm="Delete Sneha Kamat?">Delete</button>
+  </td>
+</tr>
+        
+        
+      </tbody>
+    </table>
+    <nav class="pager" aria-label="Pages">
+      
+      <span>Page 1 of 1 (1 contacts)</span>
+      
+    </nav>
+  </div>
+

thymeleaf-htmx/output/05-create-validation-errors.txt

@@ -0,0 +1,64 @@
+# request (curl notation, sent through MockMvc): curl -H 'HX-Request: true' -d 'name=&email=not-an-email&role=Developer' /contacts
+HTTP 422
+---- body (636 chars) ----
+<form id="contact-form" action="/contacts" method="post"
+        hx-post="/contacts" hx-target="this" hx-swap="outerHTML">
+    <p>
+      <label>Name <input id="name" name="name" value="" class="invalid"></label>
+      <small class="error">Name is required</small>
+    </p>
+    <p>
+      <label>Email <input id="email" name="email" value="not-an-email" class="invalid"></label>
+      <small class="error">Email must look like name@host</small>
+    </p>
+    <p>
+      <label>Role <input id="role" name="role" value="Developer"></label>
+      
+    </p>
+    <button type="submit">Create</button>
+    <a href="/contacts">Cancel</a>
+  </form>
+
+# request (curl notation, sent through MockMvc): curl -d 'name=&[email protected]&role=Tester' /contacts   (no JavaScript, no HX header)
+HTTP 422
+---- body (1461 chars) ----
+<!DOCTYPE html>
+<html lang="en">
+<head>
+  <meta charset="utf-8">
+  <meta name="viewport" content="width=device-width, initial-scale=1">
+  <title>New contact</title>
+  <!-- htmx 2 swaps 2xx/3xx only. 422 must be allowed to swap, or validation errors never appear. -->
+  <meta name="htmx-config"
+        content='{"responseHandling":[{"code":"204","swap":false},{"code":"[23]..","swap":true},{"code":"422","swap":true,"error":false},{"code":"[45]..","swap":false,"error":true},{"code":"...","swap":false}]}'>
+  <link rel="stylesheet" href="/css/app.css">
+  <script src="/webjars/htmx.org/2.0.11/dist/htmx.min.js" defer></script>
+</head>
+<body>
+  <header><a href="/contacts">Contacts</a></header>
+  <main>
+  <h1>New contact</h1>
+
+  <!-- With JS: hx-post swaps this form for the re-rendered one on a 422.
+       Without JS: the same form posts normally and the full page comes back. -->
+  <form id="contact-form" action="/contacts" method="post"
+        hx-post="/contacts" hx-target="this" hx-swap="outerHTML">
+    <p>
+      <label>Name <input id="name" name="name" value="" class="invalid"></label>
+      <small class="error">Name is required</small>
+    </p>
+    <p>
+      <label>Email <input id="email" name="email" value="[email protected]"></label>
+      
+    </p>
+    <p>
+      <label>Role <input id="role" name="role" value="Tester"></label>
+      
+    </p>
+    <button type="submit">Create</button>
+    <a href="/contacts">Cancel</a>
+  </form>
+</main>
+</body>
+</html>
+

thymeleaf-htmx/output/06-create-success.txt

@@ -0,0 +1,16 @@
+# request (curl notation, sent through MockMvc): curl -H 'HX-Request: true' -d 'name=Zoya Khan&[email protected]&role=Developer' /contacts
+HTTP 200
+Vary: HX-Request
+Vary: HX-History-Restore-Request
+HX-Redirect: /contacts
+---- body (0 chars) ----
+
+
+# request (curl notation, sent through MockMvc): curl -d 'name=Zubin Irani&[email protected]&role=Tester' /contacts
+HTTP 302
+Vary: HX-Request
+Vary: HX-History-Restore-Request
+Location: /contacts
+---- body (0 chars) ----
+
+

thymeleaf-htmx/output/07-inline-edit.txt

@@ -0,0 +1,63 @@
+# request (curl notation, sent through MockMvc): curl -H 'HX-Request: true' /contacts/1/edit        (Edit button)
+HTTP 200
+---- body (523 chars) ----
+<tr id="contact-1" class="editing">
+  <td>
+    <input name="name" value="Aarav Kulkarni">
+    
+  </td>
+  <td>
+    <input name="email" value="[email protected]">
+    
+  </td>
+  <td>
+    <input name="role" value="Developer">
+    
+  </td>
+  <td>
+    <button type="button"
+            hx-include="closest tr" hx-target="closest tr" hx-swap="outerHTML" hx-put="/contacts/1">Save</button>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-get="/contacts/1">Cancel</button>
+  </td>
+</tr>
+
+# request (curl notation, sent through MockMvc): curl -X PUT -H 'HX-Request: true' -d 'name=&email=broken&role=Architect' /contacts/1   (Save, invalid)
+HTTP 422
+---- body (625 chars) ----
+<tr id="contact-1" class="editing">
+  <td>
+    <input name="name" value="" class="invalid">
+    <small class="error">Name is required</small>
+  </td>
+  <td>
+    <input name="email" value="broken" class="invalid">
+    <small class="error">Email must look like name@host</small>
+  </td>
+  <td>
+    <input name="role" value="Architect">
+    
+  </td>
+  <td>
+    <button type="button"
+            hx-include="closest tr" hx-target="closest tr" hx-swap="outerHTML" hx-put="/contacts/1">Save</button>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-get="/contacts/1">Cancel</button>
+  </td>
+</tr>
+
+# request (curl notation, sent through MockMvc): curl -X PUT -H 'HX-Request: true' -d 'name=Aarav K.&[email protected]&role=Architect' /contacts/1   (Save, valid)
+HTTP 200
+---- body (382 chars) ----
+<tr id="contact-1">
+  <td>Aarav K.</td>
+  <td>[email protected]</td>
+  <td>Architect</td>
+  <td>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-get="/contacts/1/edit">Edit</button>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-delete="/contacts/1" hx-confirm="Delete Aarav K.?">Delete</button>
+  </td>
+</tr>
+

thymeleaf-htmx/output/08-delete.txt

@@ -0,0 +1,15 @@
+# request (curl notation, sent through MockMvc): curl -X DELETE -H 'HX-Request: true' /contacts/1
+HTTP 200
+Vary: HX-Request
+Vary: HX-History-Restore-Request
+HX-Trigger: contactsChanged
+---- body (0 chars) ----
+
+
+# request (curl notation, sent through MockMvc): curl -X DELETE -H 'HX-Request: true' /contacts/999999
+HTTP 404
+Vary: HX-Request
+Vary: HX-History-Restore-Request
+---- body (0 chars) ----
+
+

thymeleaf-htmx/output/09-delete-last-page-clamps.txt

@@ -0,0 +1,79 @@
+# deleted the 3 rows on page 5, then the table (which re-fetches page 5 after HX-Trigger) asks for page index 4
+# request (curl notation, sent through MockMvc): curl -H 'HX-Request: true' '/contacts?page=4'
+HTTP 200
+---- body (2602 chars) ----
+<div id="contact-table" hx-trigger="contactsChanged from:body" hx-target="this" hx-swap="outerHTML" hx-get="/contacts?page=3">
+    <table>
+      <thead><tr><th>Name</th><th>Email</th><th>Role</th><th></th></tr></thead>
+      <tbody>
+        
+          <tr id="contact-16">
+  <td>Pooja Verma</td>
+  <td>[email protected]</td>
+  <td>Manager</td>
+  <td>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-get="/contacts/16/edit">Edit</button>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-delete="/contacts/16" hx-confirm="Delete Pooja Verma?">Delete</button>
+  </td>
+</tr>
+        
+          <tr id="contact-17">
+  <td>Qasim Ansari</td>
+  <td>[email protected]</td>
+  <td>Developer</td>
+  <td>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-get="/contacts/17/edit">Edit</button>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-delete="/contacts/17" hx-confirm="Delete Qasim Ansari?">Delete</button>
+  </td>
+</tr>
+        
+          <tr id="contact-18">
+  <td>Rohan Sawant</td>
+  <td>[email protected]</td>
+  <td>Tester</td>
+  <td>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-get="/contacts/18/edit">Edit</button>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-delete="/contacts/18" hx-confirm="Delete Rohan Sawant?">Delete</button>
+  </td>
+</tr>
+        
+          <tr id="contact-19">
+  <td>Sneha Kamat</td>
+  <td>[email protected]</td>
+  <td>Architect</td>
+  <td>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-get="/contacts/19/edit">Edit</button>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-delete="/contacts/19" hx-confirm="Delete Sneha Kamat?">Delete</button>
+  </td>
+</tr>
+        
+          <tr id="contact-20">
+  <td>Tanmay Ghosh</td>
+  <td>[email protected]</td>
+  <td>Manager</td>
+  <td>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-get="/contacts/20/edit">Edit</button>
+    <button type="button"
+            hx-target="closest tr" hx-swap="outerHTML" hx-delete="/contacts/20" hx-confirm="Delete Tanmay Ghosh?">Delete</button>
+  </td>
+</tr>
+        
+        
+      </tbody>
+    </table>
+    <nav class="pager" aria-label="Pages">
+      <a href="/contacts?page=2" hx-target="#contact-table" hx-push-url="true" hx-get="/contacts?page=2">&laquo; Prev</a>
+      <span>Page 4 of 4 (20 contacts)</span>
+      
+    </nav>
+  </div>
+

thymeleaf-htmx/output/10-live-curl.txt

@@ -0,0 +1,35 @@
+$ curl -si http://localhost:18082/contacts | tr -d '\r' | grep -v -E '^(Date|Transfer-Encoding)' | head -10
+HTTP/1.1 200 
+Vary: HX-Request
+Vary: HX-History-Restore-Request
+Content-Type: text/html;charset=UTF-8
+Content-Language: en-US
+
+<!DOCTYPE html>
+<html lang="en">
+<head>
+  <meta charset="utf-8">
+
+$ curl -si -H 'HX-Request: true' http://localhost:18082/contacts | tr -d '\r' | grep -v -E '^(Date|Transfer-Encoding)' | head -8
+HTTP/1.1 200 
+Vary: HX-Request
+Vary: HX-History-Restore-Request
+Content-Type: text/html;charset=UTF-8
+Content-Language: en-US
+
+<div id="contact-table" hx-trigger="contactsChanged from:body" hx-target="this" hx-swap="outerHTML" hx-get="/contacts?page=0">
+    <table>
+
+$ curl -s -o /dev/null -w '%{http_code} %{content_type}\n' http://localhost:18082/webjars/htmx.org/dist/htmx.min.js
+200 text/javascript
+
+$ curl -si -X DELETE -H 'HX-Request: true' http://localhost:18082/contacts/23
+HTTP/1.1 200 
+Vary: HX-Request
+Vary: HX-History-Restore-Request
+HX-Trigger: contactsChanged
+Content-Length: 0
+
+
+$ curl -si -X DELETE -H 'HX-Request: true' http://localhost:18082/contacts/23   (again)
+HTTP/1.1 404 

thymeleaf-htmx/output/11-browser-check.txt

@@ -0,0 +1,52 @@
+== 1. load, then search without a page reload
+htmx loaded: object 2.0.11
+rows on first page: 5
+after typing "kamat": ["Sneha Kamat"]
+address bar: /contacts?q=kamat
+elements with id contact-table: 1
+document survived (no reload): same-document
+
+== 2. pagination + back button
+page 2 names: ["Farah Sheikh","Gauri Deshpande","Harsh Mehta","Isha Rao","Jayesh Pawar"]
+address bar: /contacts?page=1
+Back request: GET /contacts?q=  HX-Request=true HX-History-Restore-Request=true
+after Back: h1="Contacts", pager="Page 1 of 5 (23 contacts)"
+
+== 3. inline edit with a validation error
+row still editing, errors: ["Name is required","Email must look like name@host"]
+saved, row is read-only again: ["Aarav K.","Bhavna Joshi","Chinmay Desai","Divya Nair","Eshaan Patil"]
+
+== 4. delete with confirm
+confirm dialog: "Delete Aarav K.?"
+pager after delete: "Page 1 of 5 (22 contacts)"
+requests caused by one delete: ["DELETE /contacts/1  HX-Request=true HX-History-Restore-Request=-","GET /contacts?page=0  HX-Request=true HX-History-Restore-Request=-"]
+
+== 5. create form: 422 re-render, then success
+errors shown in place: ["Name is required","Email must look like name@host"]
+still on: /contacts/new, typed email kept: x
+HX-Redirect landed on: /contacts
+
+== 6. the two status-code traps, observed
+DELETE answered 204: rows before=5, after=5 (row not removed)
+htmx-config meta present: 0
+Save answered 422 without the meta tag: errors visible = 0
+
+== requests the browser made (excluding static files)
+GET /contacts  HX-Request=- HX-History-Restore-Request=-
+GET /contacts?q=kamat  HX-Request=true HX-History-Restore-Request=-
+GET /contacts?q=  HX-Request=true HX-History-Restore-Request=-
+GET /contacts?page=1  HX-Request=true HX-History-Restore-Request=-
+GET /contacts?q=  HX-Request=true HX-History-Restore-Request=true
+GET /contacts/1/edit  HX-Request=true HX-History-Restore-Request=-
+PUT /contacts/1  HX-Request=true HX-History-Restore-Request=-
+PUT /contacts/1  HX-Request=true HX-History-Restore-Request=-
+DELETE /contacts/1  HX-Request=true HX-History-Restore-Request=-
+GET /contacts?page=0  HX-Request=true HX-History-Restore-Request=-
+GET /contacts/new  HX-Request=- HX-History-Restore-Request=-
+POST /contacts  HX-Request=true HX-History-Restore-Request=-
+POST /contacts  HX-Request=true HX-History-Restore-Request=-
+GET /contacts  HX-Request=- HX-History-Restore-Request=-
+DELETE /contacts/2  HX-Request=true HX-History-Restore-Request=-
+GET /contacts  HX-Request=- HX-History-Restore-Request=-
+GET /contacts/2/edit  HX-Request=true HX-History-Restore-Request=-
+PUT /contacts/2  HX-Request=true HX-History-Restore-Request=-

thymeleaf-htmx/pom.xml

@@ -0,0 +1,80 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
+  <modelVersion>4.0.0</modelVersion>
+
+  <parent>
+    <groupId>org.springframework.boot</groupId>
+    <artifactId>spring-boot-starter-parent</artifactId>
+    <version>4.1.2</version>
+    <relativePath/>
+  </parent>
+
+  <groupId>com.ankurm</groupId>
+  <artifactId>thymeleaf-htmx</artifactId>
+  <version>1.0.0</version>
+  <name>thymeleaf-htmx</name>
+  <description>Server-side CRUD UI with Spring Boot 4, Thymeleaf and htmx: no JS framework</description>
+
+  <properties>
+    <java.version>25</java.version>
+    <htmx.version>2.0.11</htmx.version>
+  </properties>
+
+  <dependencies>
+    <dependency>
+      <groupId>org.springframework.boot</groupId>
+      <artifactId>spring-boot-starter-webmvc</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>org.springframework.boot</groupId>
+      <artifactId>spring-boot-starter-thymeleaf</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>org.springframework.boot</groupId>
+      <artifactId>spring-boot-starter-validation</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>org.springframework.boot</groupId>
+      <artifactId>spring-boot-starter-data-jpa</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>com.h2database</groupId>
+      <artifactId>h2</artifactId>
+      <scope>runtime</scope>
+    </dependency>
+
+    <!-- htmx as a WebJar: the jar is pinned in this pom, served from /webjars/**. -->
+    <dependency>
+      <groupId>org.webjars.npm</groupId>
+      <artifactId>htmx.org</artifactId>
+      <version>${htmx.version}</version>
+    </dependency>
+    <!-- lets templates ask for /webjars/htmx.org/dist/htmx.min.js without the version -->
+    <dependency>
+      <groupId>org.webjars</groupId>
+      <artifactId>webjars-locator-lite</artifactId>
+    </dependency>
+
+    <dependency>
+      <groupId>org.springframework.boot</groupId>
+      <artifactId>spring-boot-starter-webmvc-test</artifactId>
+      <scope>test</scope>
+    </dependency>
+    <dependency>
+      <groupId>org.springframework.boot</groupId>
+      <artifactId>spring-boot-starter-thymeleaf-test</artifactId>
+      <scope>test</scope>
+    </dependency>
+  </dependencies>
+
+  <build>
+    <plugins>
+      <plugin>
+        <groupId>org.springframework.boot</groupId>
+        <artifactId>spring-boot-maven-plugin</artifactId>
+      </plugin>
+    </plugins>
+  </build>
+</project>

thymeleaf-htmx/scripts/browser-check.sh

@@ -0,0 +1,10 @@
+#!/usr/bin/env bash
+# Needs Node 20+ and a one-time `npx playwright install chromium`. Starts a FRESH jar (data is mutated).
+set -euo pipefail
+cd "$(dirname "$0")/.."
+PORT=${PORT:-18083}
+java -Xmx256m -jar target/thymeleaf-htmx-1.0.0.jar --server.port=$PORT > /tmp/thymeleaf-htmx-browser.log 2>&1 &
+PID=$!
+trap 'kill $PID 2>/dev/null || true' EXIT
+for i in $(seq 1 60); do curl -s -o /dev/null localhost:$PORT/contacts && break; sleep 1; done
+(cd browser-check && npm install --silent && node check.mjs http://localhost:$PORT)

thymeleaf-htmx/scripts/live-demo.sh

@@ -0,0 +1,24 @@
+#!/usr/bin/env bash
+# Boots the packaged jar on a private port and shows the same URL answering twice.
+set -euo pipefail
+cd "$(dirname "$0")/.."
+PORT=${PORT:-18082}
+java -Xmx256m -jar target/thymeleaf-htmx-1.0.0.jar --server.port=$PORT > /tmp/thymeleaf-htmx-live.log 2>&1 &
+PID=$!
+trap 'kill $PID 2>/dev/null || true' EXIT
+for i in $(seq 1 60); do curl -s -o /dev/null localhost:$PORT/contacts && break; sleep 1; done
+B=http://localhost:$PORT
+echo "\$ curl -si $B/contacts | tr -d '\r' | grep -v -E '^(Date|Transfer-Encoding)' | head -10"
+curl -si $B/contacts | tr -d '\r' | grep -v -E '^(Date|Transfer-Encoding)' | head -10
+echo
+echo "\$ curl -si -H 'HX-Request: true' $B/contacts | tr -d '\r' | grep -v -E '^(Date|Transfer-Encoding)' | head -8"
+curl -si -H 'HX-Request: true' $B/contacts | tr -d '\r' | grep -v -E '^(Date|Transfer-Encoding)' | head -8
+echo
+echo "\$ curl -s -o /dev/null -w '%{http_code} %{content_type}\n' $B/webjars/htmx.org/dist/htmx.min.js"
+curl -s -o /dev/null -w '%{http_code} %{content_type}\n' $B/webjars/htmx.org/dist/htmx.min.js
+echo
+echo "\$ curl -si -X DELETE -H 'HX-Request: true' $B/contacts/23"
+curl -si -X DELETE -H 'HX-Request: true' $B/contacts/23 | tr -d '\r' | grep -v '^Date'
+echo
+echo "\$ curl -si -X DELETE -H 'HX-Request: true' $B/contacts/23   (again)"
+curl -si -X DELETE -H 'HX-Request: true' $B/contacts/23 | head -1

thymeleaf-htmx/scripts/run-all.sh

@@ -0,0 +1,12 @@
+#!/usr/bin/env bash
+# Regenerates every file in output/ : the test suite writes the MockMvc transcripts,
+# then a real Tomcat is started and driven with curl for 10-live-*.txt.
+set -euo pipefail
+cd "$(dirname "$0")/.."
+rm -rf output && mkdir -p output
+mvn -B -q test > /tmp/thymeleaf-htmx-mvn.log 2>&1 || { cat /tmp/thymeleaf-htmx-mvn.log; exit 1; }
+mvn -B -q -DskipTests package > /dev/null 2>&1
+./scripts/live-demo.sh > output/10-live-curl.txt
+grep -E 'Tests run' target/surefire-reports/*.txt | sed 's#.*/##' >  output/00-mvn-test.txt
+if [ -d browser-check/node_modules ] || command -v node >/dev/null; then ./scripts/browser-check.sh > output/11-browser-check.txt; fi
+ls output

thymeleaf-htmx/src/main/java/com/ankurm/thymeleafhtmx/Contact.java

@@ -0,0 +1,45 @@
+package com.ankurm.thymeleafhtmx;
+
+import jakarta.persistence.Column;
+import jakarta.persistence.Entity;
+import jakarta.persistence.GeneratedValue;
+import jakarta.persistence.GenerationType;
+import jakarta.persistence.Id;
+
+/** The persistent record. The form is a separate type ({@link ContactForm}) so that
+ *  validation rules and request binding never touch the entity. */
+@Entity
+public class Contact {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private Long id;
+
+    @Column(nullable = false)
+    private String name;
+
+    @Column(nullable = false, unique = true)
+    private String email;
+
+    @Column(nullable = false)
+    private String role;
+
+    protected Contact() { }
+
+    public Contact(String name, String email, String role) {
+        this.name = name;
+        this.email = email;
+        this.role = role;
+    }
+
+    public void apply(ContactForm form) {
+        this.name = form.getName();
+        this.email = form.getEmail();
+        this.role = form.getRole();
+    }
+
+    public Long getId() { return id; }
+    public String getName() { return name; }
+    public String getEmail() { return email; }
+    public String getRole() { return role; }
+}

thymeleaf-htmx/src/main/java/com/ankurm/thymeleafhtmx/ContactController.java

@@ -0,0 +1,152 @@
+package com.ankurm.thymeleafhtmx;
+
+import jakarta.servlet.http.HttpServletRequest;
+import jakarta.servlet.http.HttpServletResponse;
+import jakarta.validation.Valid;
+import org.springframework.data.domain.Page;
+import org.springframework.data.domain.PageRequest;
+import org.springframework.data.domain.Pageable;
+import org.springframework.data.domain.Sort;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.ResponseEntity;
+import org.springframework.stereotype.Controller;
+import org.springframework.ui.Model;
+import org.springframework.validation.BindingResult;
+import org.springframework.web.bind.annotation.DeleteMapping;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.ModelAttribute;
+import org.springframework.web.bind.annotation.PathVariable;
+import org.springframework.web.bind.annotation.PostMapping;
+import org.springframework.web.bind.annotation.PutMapping;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RequestParam;
+import org.springframework.web.server.ResponseStatusException;
+import org.springframework.web.util.UriComponentsBuilder;
+
+@Controller
+@RequestMapping("/contacts")
+class ContactController {
+
+    static final int PAGE_SIZE = 5;
+
+    private final ContactRepository repo;
+
+    ContactController(ContactRepository repo) {
+        this.repo = repo;
+    }
+
+    // ---- list + search + pagination: one handler, two representations ----------------------
+
+    @GetMapping
+    String list(@RequestParam(defaultValue = "") String q,
+                @RequestParam(defaultValue = "0") int page,
+                Model model, HttpServletRequest request) {
+        Page<Contact> result = find(q, page);
+        if (page > 0 && result.getTotalPages() > 0 && page >= result.getTotalPages()) {
+            // Page.getNumber() echoes the requested index even past the end, so compare against
+            // getTotalPages(). Clamp to the last page (what happens after deleting its last row).
+            result = find(q, result.getTotalPages() - 1);
+        }
+        model.addAttribute("page", result);
+        model.addAttribute("q", q);
+        model.addAttribute("selfUrl", url(q, result.getNumber()));
+        model.addAttribute("prevUrl", result.hasPrevious() ? url(q, result.getNumber() - 1) : null);
+        model.addAttribute("nextUrl", result.hasNext() ? url(q, result.getNumber() + 1) : null);
+        return Htmx.wantsFragment(request) ? "contacts/list :: table" : "contacts/list";
+    }
+
+    /** Built here, not in the template, so an empty search never produces "?q=&page=1". */
+    private static String url(String q, int page) {
+        return UriComponentsBuilder.fromPath("/contacts")
+                .queryParamIfPresent("q", q.isBlank() ? java.util.Optional.empty() : java.util.Optional.of(q))
+                .queryParam("page", page)
+                .encode().build().toUriString();
+    }
+
+    private Page<Contact> find(String q, int page) {
+        Pageable pageable = PageRequest.of(Math.max(page, 0), PAGE_SIZE, Sort.by("name").and(Sort.by("id")));
+        return q.isBlank()
+                ? repo.findAll(pageable)
+                : repo.findByNameContainingIgnoreCaseOrEmailContainingIgnoreCase(q, q, pageable);
+    }
+
+    // ---- create -----------------------------------------------------------------------------
+
+    @GetMapping("/new")
+    String newForm(Model model, HttpServletRequest request) {
+        model.addAttribute("contactForm", new ContactForm());
+        return Htmx.wantsFragment(request) ? "contacts/new :: form" : "contacts/new";
+    }
+
+    @PostMapping
+    Object create(@Valid @ModelAttribute ContactForm contactForm, BindingResult errors,
+                  HttpServletRequest request, HttpServletResponse response) {
+        if (repo.existsByEmailIgnoreCase(contactForm.getEmail() == null ? "" : contactForm.getEmail())) {
+            errors.rejectValue("email", "duplicate", "That email is already in the list");
+        }
+        if (errors.hasErrors()) {
+            response.setStatus(HttpStatus.UNPROCESSABLE_ENTITY.value());
+            return Htmx.wantsFragment(request) ? "contacts/new :: form" : "contacts/new";
+        }
+        repo.save(newContact(contactForm));
+        if (Htmx.wantsFragment(request)) {
+            // htmx follows HX-Redirect with a full page navigation
+            return ResponseEntity.ok().header("HX-Redirect", "/contacts").build();
+        }
+        return "redirect:/contacts"; // classic post-redirect-get for plain browsers
+    }
+
+    private static Contact newContact(ContactForm f) {
+        Contact c = new Contact(f.getName(), f.getEmail(), f.getRole());
+        return c;
+    }
+
+    // ---- inline edit: three row states (read, edit, edit-with-errors) ------------------------
+
+    @GetMapping("/{id}")
+    String row(@PathVariable Long id, Model model) {
+        model.addAttribute("contact", load(id));
+        return "contacts/fragments :: row";
+    }
+
+    @GetMapping("/{id}/edit")
+    String editRow(@PathVariable Long id, Model model) {
+        Contact c = load(id);
+        model.addAttribute("contact", c);
+        model.addAttribute("contactForm", ContactForm.of(c));
+        return "contacts/fragments :: editRow";
+    }
+
+    @PutMapping("/{id}")
+    String update(@PathVariable Long id, @Valid @ModelAttribute ContactForm contactForm,
+                  BindingResult errors, Model model, HttpServletResponse response) {
+        Contact c = load(id);
+        model.addAttribute("contact", c);
+        String email = contactForm.getEmail() == null ? "" : contactForm.getEmail();
+        if (repo.existsByEmailIgnoreCaseAndIdNot(email, id)) {
+            errors.rejectValue("email", "duplicate", "That email is already in the list");
+        }
+        if (errors.hasErrors()) {
+            response.setStatus(HttpStatus.UNPROCESSABLE_ENTITY.value());
+            return "contacts/fragments :: editRow";
+        }
+        c.apply(contactForm);
+        repo.save(c);
+        return "contacts/fragments :: row";
+    }
+
+    // ---- delete -----------------------------------------------------------------------------
+
+    /** 200 with an empty body, NOT 204: htmx 2 does not swap a 204, so the row would stay.
+     *  HX-Trigger tells the table to refresh itself so the pager and page contents stay honest. */
+    @DeleteMapping("/{id}")
+    ResponseEntity<Void> delete(@PathVariable Long id) {
+        load(id);
+        repo.deleteById(id);
+        return ResponseEntity.ok().header("HX-Trigger", "contactsChanged").build();
+    }
+
+    private Contact load(Long id) {
+        return repo.findById(id).orElseThrow(() -> new ResponseStatusException(HttpStatus.NOT_FOUND));
+    }
+}

thymeleaf-htmx/src/main/java/com/ankurm/thymeleafhtmx/ContactForm.java

@@ -0,0 +1,41 @@
+package com.ankurm.thymeleafhtmx;
+
+import jakarta.validation.constraints.Email;
+import jakarta.validation.constraints.NotBlank;
+import jakarta.validation.constraints.Size;
+
+/** What the browser posts. A plain getter/setter bean: th:field reads properties through getters
+ *  and this is the shape the Thymeleaf-Spring binding documentation shows. (Whether a record
+ *  would also work was not tested here.) */
+public class ContactForm {
+
+    @NotBlank(message = "Name is required")
+    @Size(max = 60, message = "Name must be at most 60 characters")
+    private String name;
+
+    @NotBlank(message = "Email is required")
+    @Email(message = "Email must look like name@host")
+    private String email;
+
+    @NotBlank(message = "Role is required")
+    private String role;
+
+    public ContactForm() { }
+
+    public ContactForm(String name, String email, String role) {
+        this.name = name;
+        this.email = email;
+        this.role = role;
+    }
+
+    public static ContactForm of(Contact c) {
+        return new ContactForm(c.getName(), c.getEmail(), c.getRole());
+    }
+
+    public String getName() { return name; }
+    public void setName(String name) { this.name = name; }
+    public String getEmail() { return email; }
+    public void setEmail(String email) { this.email = email; }
+    public String getRole() { return role; }
+    public void setRole(String role) { this.role = role; }
+}

thymeleaf-htmx/src/main/java/com/ankurm/thymeleafhtmx/ContactRepository.java

@@ -0,0 +1,15 @@
+package com.ankurm.thymeleafhtmx;
+
+import org.springframework.data.domain.Page;
+import org.springframework.data.domain.Pageable;
+import org.springframework.data.jpa.repository.JpaRepository;
+
+public interface ContactRepository extends JpaRepository<Contact, Long> {
+
+    Page<Contact> findByNameContainingIgnoreCaseOrEmailContainingIgnoreCase(
+            String name, String email, Pageable pageable);
+
+    boolean existsByEmailIgnoreCase(String email);
+
+    boolean existsByEmailIgnoreCaseAndIdNot(String email, Long id);
+}

thymeleaf-htmx/src/main/java/com/ankurm/thymeleafhtmx/Htmx.java

@@ -0,0 +1,18 @@
+package com.ankurm.thymeleafhtmx;
+
+import jakarta.servlet.http.HttpServletRequest;
+
+/** The two request headers that decide "fragment or full page". */
+final class Htmx {
+
+    private Htmx() { }
+
+    /** True for an htmx-issued request that wants a fragment.
+     *  htmx also sends HX-Request on a history-cache miss, but then it swaps the response
+     *  into the whole body, so that case needs the full page. */
+    static boolean wantsFragment(HttpServletRequest request) {
+        boolean hx = "true".equals(request.getHeader("HX-Request"));
+        boolean historyRestore = "true".equals(request.getHeader("HX-History-Restore-Request"));
+        return hx && !historyRestore;
+    }
+}

thymeleaf-htmx/src/main/java/com/ankurm/thymeleafhtmx/SeedData.java

@@ -0,0 +1,27 @@
+package com.ankurm.thymeleafhtmx;
+
+import org.springframework.boot.ApplicationRunner;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+/** 23 rows, so that a page size of 5 gives five pages and the last one is short. */
+@Configuration
+class SeedData {
+
+    @Bean
+    ApplicationRunner seed(ContactRepository repo) {
+        return args -> {
+            if (repo.count() > 0) return;
+            String[] names = {"Aarav Kulkarni", "Bhavna Joshi", "Chinmay Desai", "Divya Nair", "Eshaan Patil",
+                    "Farah Sheikh", "Gauri Deshpande", "Harsh Mehta", "Isha Rao", "Jayesh Pawar",
+                    "Kavya Menon", "Lakshman Iyer", "Meera Shah", "Neel Bhatt", "Omkar Gokhale",
+                    "Pooja Verma", "Qasim Ansari", "Rohan Sawant", "Sneha Kamat", "Tanmay Ghosh",
+                    "Uma Pillai", "Vikram Singh", "Yash Thakur"};
+            String[] roles = {"Developer", "Tester", "Architect", "Manager"};
+            for (int i = 0; i < names.length; i++) {
+                String local = names[i].toLowerCase().replace(' ', '.');
+                repo.save(new Contact(names[i], local + "@example.com", roles[i % roles.length]));
+            }
+        };
+    }
+}

thymeleaf-htmx/src/main/java/com/ankurm/thymeleafhtmx/ThymeleafHtmxApplication.java

@@ -0,0 +1,11 @@
+package com.ankurm.thymeleafhtmx;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class ThymeleafHtmxApplication {
+    public static void main(String[] args) {
+        SpringApplication.run(ThymeleafHtmxApplication.class, args);
+    }
+}

thymeleaf-htmx/src/main/java/com/ankurm/thymeleafhtmx/VaryHtmxFilter.java

@@ -0,0 +1,23 @@
+package com.ankurm.thymeleafhtmx;
+
+import jakarta.servlet.FilterChain;
+import jakarta.servlet.ServletException;
+import jakarta.servlet.http.HttpServletRequest;
+import jakarta.servlet.http.HttpServletResponse;
+import org.springframework.stereotype.Component;
+import org.springframework.web.filter.OncePerRequestFilter;
+
+import java.io.IOException;
+
+/** The same URL now has two representations. Tell caches, or the back button will show a fragment. */
+@Component
+class VaryHtmxFilter extends OncePerRequestFilter {
+
+    @Override
+    protected void doFilterInternal(HttpServletRequest req, HttpServletResponse res, FilterChain chain)
+            throws ServletException, IOException {
+        res.addHeader("Vary", "HX-Request");
+        res.addHeader("Vary", "HX-History-Restore-Request");
+        chain.doFilter(req, res);
+    }
+}

thymeleaf-htmx/src/main/resources/application.properties

@@ -0,0 +1,2 @@
+spring.application.name=thymeleaf-htmx
+spring.jpa.open-in-view=false

thymeleaf-htmx/src/main/resources/static/css/app.css

@@ -0,0 +1,8 @@
+body { font-family: system-ui, sans-serif; max-width: 52rem; margin: 0 auto; padding: 1rem; }
+table { border-collapse: collapse; width: 100%; }
+th, td { text-align: left; padding: .4rem .6rem; border-bottom: 1px solid #ddd; }
+input.invalid { border: 2px solid #c0392b; }
+.error { color: #c0392b; display: block; }
+.pager { display: flex; gap: 1rem; margin-top: .75rem; }
+.htmx-request { opacity: .6; }
+tr.htmx-swapping { opacity: 0; transition: opacity .3s ease-out; }

thymeleaf-htmx/src/main/resources/templates/contacts/fragments.html

@@ -0,0 +1,45 @@
+<!DOCTYPE html>
+<html xmlns:th="http://www.thymeleaf.org">
+<body>
+
+<!-- read-only row -->
+<tr th:fragment="row" th:id="${'contact-' + contact.id}">
+  <td th:text="${contact.name}">Name</td>
+  <td th:text="${contact.email}">email</td>
+  <td th:text="${contact.role}">role</td>
+  <td>
+    <button type="button"
+            th:attr="hx-get=@{/contacts/{id}/edit(id=${contact.id})}"
+            hx-target="closest tr" hx-swap="outerHTML">Edit</button>
+    <button type="button"
+            th:attr="hx-delete=@{/contacts/{id}(id=${contact.id})},hx-confirm='Delete ' + ${contact.name} + '?'"
+            hx-target="closest tr" hx-swap="outerHTML">Delete</button>
+  </td>
+</tr>
+
+<!-- edit row: also what a failed save returns, with errors -->
+<tr th:fragment="editRow" th:id="${'contact-' + contact.id}" class="editing">
+  <td>
+    <input name="name" th:value="${contactForm.name}" th:classappend="${#fields.hasErrors('contactForm.name')} ? 'invalid'">
+    <small class="error" th:if="${#fields.hasErrors('contactForm.name')}" th:errors="${contactForm.name}">error</small>
+  </td>
+  <td>
+    <input name="email" th:value="${contactForm.email}" th:classappend="${#fields.hasErrors('contactForm.email')} ? 'invalid'">
+    <small class="error" th:if="${#fields.hasErrors('contactForm.email')}" th:errors="${contactForm.email}">error</small>
+  </td>
+  <td>
+    <input name="role" th:value="${contactForm.role}" th:classappend="${#fields.hasErrors('contactForm.role')} ? 'invalid'">
+    <small class="error" th:if="${#fields.hasErrors('contactForm.role')}" th:errors="${contactForm.role}">error</small>
+  </td>
+  <td>
+    <button type="button"
+            th:attr="hx-put=@{/contacts/{id}(id=${contact.id})}"
+            hx-include="closest tr" hx-target="closest tr" hx-swap="outerHTML">Save</button>
+    <button type="button"
+            th:attr="hx-get=@{/contacts/{id}(id=${contact.id})}"
+            hx-target="closest tr" hx-swap="outerHTML">Cancel</button>
+  </td>
+</tr>
+
+</body>
+</html>

thymeleaf-htmx/src/main/resources/templates/contacts/list.html

@@ -0,0 +1,43 @@
+<!DOCTYPE html>
+<html xmlns:th="http://www.thymeleaf.org"
+      th:replace="~{layout/base :: layout(~{::title}, ~{::main})}">
+<head><title>Contacts</title></head>
+<body>
+<main>
+  <h1>Contacts</h1>
+
+  <p><a th:href="@{/contacts/new}">New contact</a></p>
+
+  <form th:action="@{/contacts}" method="get" role="search">
+    <input type="search" name="q" th:value="${q}" placeholder="Search name or email"
+           hx-get="/contacts" hx-trigger="input changed delay:300ms, search"
+           hx-target="#contact-table" hx-swap="outerHTML" hx-push-url="true">
+    <noscript><button type="submit">Search</button></noscript>
+  </form>
+
+  <!-- th:fragment "table" is exactly what an htmx request gets back -->
+  <div id="contact-table" th:fragment="table"
+       th:attr="hx-get=${selfUrl}"
+       hx-trigger="contactsChanged from:body" hx-target="this" hx-swap="outerHTML">
+    <table>
+      <thead><tr><th>Name</th><th>Email</th><th>Role</th><th></th></tr></thead>
+      <tbody>
+        <th:block th:each="contact : ${page.content}">
+          <tr th:replace="~{contacts/fragments :: row}"></tr>
+        </th:block>
+        <tr th:if="${page.empty}"><td colspan="4">No contacts match.</td></tr>
+      </tbody>
+    </table>
+    <nav class="pager" aria-label="Pages">
+      <a th:if="${prevUrl != null}"
+         th:href="${prevUrl}" th:attr="hx-get=${prevUrl}"
+         hx-target="#contact-table" hx-push-url="true">&laquo; Prev</a>
+      <span th:text="${'Page ' + (page.number + 1) + ' of ' + (page.totalPages == 0 ? 1 : page.totalPages) + ' (' + page.totalElements + ' contacts)'}">Page 1 of 1</span>
+      <a th:if="${nextUrl != null}"
+         th:href="${nextUrl}" th:attr="hx-get=${nextUrl}"
+         hx-target="#contact-table" hx-push-url="true">Next &raquo;</a>
+    </nav>
+  </div>
+</main>
+</body>
+</html>

thymeleaf-htmx/src/main/resources/templates/contacts/new.html

@@ -0,0 +1,30 @@
+<!DOCTYPE html>
+<html xmlns:th="http://www.thymeleaf.org"
+      th:replace="~{layout/base :: layout(~{::title}, ~{::main})}">
+<head><title>New contact</title></head>
+<body>
+<main>
+  <h1>New contact</h1>
+
+  <!-- With JS: hx-post swaps this form for the re-rendered one on a 422.
+       Without JS: the same form posts normally and the full page comes back. -->
+  <form id="contact-form" th:fragment="form" th:action="@{/contacts}" method="post"
+        th:object="${contactForm}" hx-post="/contacts" hx-target="this" hx-swap="outerHTML">
+    <p>
+      <label>Name <input th:field="*{name}" th:errorclass="invalid"></label>
+      <small class="error" th:if="${#fields.hasErrors('name')}" th:errors="*{name}">error</small>
+    </p>
+    <p>
+      <label>Email <input th:field="*{email}" th:errorclass="invalid"></label>
+      <small class="error" th:if="${#fields.hasErrors('email')}" th:errors="*{email}">error</small>
+    </p>
+    <p>
+      <label>Role <input th:field="*{role}" th:errorclass="invalid"></label>
+      <small class="error" th:if="${#fields.hasErrors('role')}" th:errors="*{role}">error</small>
+    </p>
+    <button type="submit">Create</button>
+    <a th:href="@{/contacts}">Cancel</a>
+  </form>
+</main>
+</body>
+</html>

thymeleaf-htmx/src/main/resources/templates/layout/base.html

@@ -0,0 +1,18 @@
+<!DOCTYPE html>
+<html lang="en" xmlns:th="http://www.thymeleaf.org"
+      th:fragment="layout(title, content)">
+<head>
+  <meta charset="utf-8">
+  <meta name="viewport" content="width=device-width, initial-scale=1">
+  <title th:replace="${title}">Contacts</title>
+  <!-- htmx 2 swaps 2xx/3xx only. 422 must be allowed to swap, or validation errors never appear. -->
+  <meta name="htmx-config"
+        content='{"responseHandling":[{"code":"204","swap":false},{"code":"[23]..","swap":true},{"code":"422","swap":true,"error":false},{"code":"[45]..","swap":false,"error":true},{"code":"...","swap":false}]}'>
+  <link rel="stylesheet" th:href="@{/css/app.css}">
+  <script th:src="@{/webjars/htmx.org/dist/htmx.min.js}" defer></script>
+</head>
+<body>
+  <header><a th:href="@{/contacts}">Contacts</a></header>
+  <main th:replace="${content}">page content goes here</main>
+</body>
+</html>

thymeleaf-htmx/src/test/java/com/ankurm/thymeleafhtmx/ContactUiTest.java

@@ -0,0 +1,237 @@
+package com.ankurm.thymeleafhtmx;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.webmvc.test.autoconfigure.AutoConfigureMockMvc;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.http.MediaType;
+import org.springframework.test.web.servlet.MockMvc;
+import org.springframework.test.web.servlet.MvcResult;
+import org.springframework.transaction.annotation.Transactional;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.delete;
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.post;
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.put;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
+
+/** The whole UI contract through MockMvc. The seed data is 23 contacts sorted by name, page size 5. */
+@SpringBootTest
+@AutoConfigureMockMvc
+@Transactional
+class ContactUiTest {
+
+    @Autowired MockMvc mvc;
+    @Autowired ContactRepository repo;
+
+    private static final String[] HEADERS = {"Vary", "HX-Redirect", "HX-Trigger", "Location"};
+
+    // ---- 1. same URL, two representations -----------------------------------------------
+
+    @Test
+    void fullPageVersusFragment() throws Exception {
+        MvcResult full = mvc.perform(get("/contacts")).andExpect(status().isOk()).andReturn();
+        MvcResult frag = mvc.perform(get("/contacts").header("HX-Request", "true"))
+                .andExpect(status().isOk()).andReturn();
+
+        String f = full.getResponse().getContentAsString();
+        String h = frag.getResponse().getContentAsString();
+
+        assertThat(f).contains("<!DOCTYPE html>", "<title>Contacts</title>", "<header>", "<table>");
+        assertThat(h).doesNotContain("<!DOCTYPE", "<html", "<head", "<title>", "<header>");
+        assertThat(h.strip()).startsWith("<div id=\"contact-table\"").endsWith("</div>");
+        assertThat(h).contains("<table>", "Page 1 of 5 (23 contacts)");
+        assertThat(h.length()).isLessThan(f.length());
+        // a cache must key on the header, or the back button shows a fragment
+        assertThat(full.getResponse().getHeaders("Vary")).contains("HX-Request", "HX-History-Restore-Request");
+        assertThat(frag.getResponse().getHeaders("Vary")).contains("HX-Request", "HX-History-Restore-Request");
+
+        new Transcript("01-full-page-vs-fragment.txt")
+                .exchange("curl /contacts", full, HEADERS)
+                .exchange("curl -H 'HX-Request: true' /contacts", frag, HEADERS)
+                .write();
+    }
+
+    @Test
+    void historyRestoreMissNeedsTheFullPage() throws Exception {
+        MvcResult r = mvc.perform(get("/contacts?page=1")
+                        .header("HX-Request", "true").header("HX-History-Restore-Request", "true"))
+                .andExpect(status().isOk()).andReturn();
+        assertThat(r.getResponse().getContentAsString()).contains("<!DOCTYPE html>", "<title>Contacts</title>");
+        new Transcript("02-history-restore-gets-full-page.txt")
+                .note("htmx sends BOTH headers when the history cache misses; it swaps the reply into <body>")
+                .exchange("curl -H 'HX-Request: true' -H 'HX-History-Restore-Request: true' '/contacts?page=1'",
+                        r, "Vary")
+                .write();
+    }
+
+    @Test
+    void layoutWiresHtmxFromTheWebJar() throws Exception {
+        String page = mvc.perform(get("/contacts")).andReturn().getResponse().getContentAsString();
+        assertThat(page).contains("<script src=\"/webjars/htmx.org/2.0.11/dist/htmx.min.js\" defer></script>");
+        MvcResult js = mvc.perform(get("/webjars/htmx.org/2.0.11/dist/htmx.min.js")).andExpect(status().isOk()).andReturn();
+        assertThat(js.getResponse().getContentAsString()).contains("2.0.11");
+        new Transcript("03-htmx-webjar.txt")
+                .note("script tag as rendered (the template asks for /webjars/htmx.org/dist/htmx.min.js, no version)")
+                .note(page.lines().filter(l -> l.contains("htmx.min.js")).findFirst().orElseThrow().strip())
+                .note("GET /webjars/htmx.org/2.0.11/dist/htmx.min.js -> " + js.getResponse().getStatus()
+                        + ", " + js.getResponse().getContentLength() + " bytes, Content-Type "
+                        + js.getResponse().getContentType())
+                .write();
+    }
+
+    // ---- 2. pagination and search ------------------------------------------------------
+
+    @Test
+    void pagination() throws Exception {
+        MvcResult last = mvc.perform(get("/contacts?page=4").header("HX-Request", "true")).andReturn();
+        String body = last.getResponse().getContentAsString();
+        assertThat(body).contains("Page 5 of 5 (23 contacts)", "Yash Thakur", "Vikram Singh")
+                .doesNotContain("Next &raquo;").contains("Prev");
+        assertThat(body.split("<tr id=", -1).length - 1).isEqualTo(3);
+
+        // past the end clamps to the last page rather than rendering an empty table
+        MvcResult beyond = mvc.perform(get("/contacts?page=99").header("HX-Request", "true")).andReturn();
+        assertThat(beyond.getResponse().getContentAsString()).contains("Page 5 of 5");
+
+        MvcResult search = mvc.perform(get("/contacts?q=KAMAT").header("HX-Request", "true")).andReturn();
+        String s = search.getResponse().getContentAsString();
+        assertThat(s).contains("Sneha Kamat", "Page 1 of 1 (1 contacts)").doesNotContain("Aarav");
+
+        new Transcript("04-pagination-and-search.txt")
+                .exchange("curl -H 'HX-Request: true' '/contacts?page=4'", last)
+                .exchange("curl -H 'HX-Request: true' '/contacts?page=99'", beyond)
+                .exchange("curl -H 'HX-Request: true' '/contacts?q=KAMAT'", search)
+                .write();
+    }
+
+    // ---- 3. create form with validation -----------------------------------------------
+
+    @Test
+    void invalidCreateReRendersTheFormWith422() throws Exception {
+        MvcResult hx = mvc.perform(post("/contacts").header("HX-Request", "true")
+                        .contentType(MediaType.APPLICATION_FORM_URLENCODED)
+                        .param("name", "").param("email", "not-an-email").param("role", "Developer"))
+                .andExpect(status().isUnprocessableContent()).andReturn();
+        String b = hx.getResponse().getContentAsString();
+        assertThat(b).startsWith("<form id=\"contact-form\"").doesNotContain("<html");
+        assertThat(b).contains("Name is required", "Email must look like name@host");
+        assertThat(b).contains("value=\"not-an-email\"", "value=\"Developer\"");   // user input preserved
+        assertThat(b).contains("class=\"invalid\"");
+        assertThat(repo.count()).isEqualTo(23);
+
+        MvcResult plain = mvc.perform(post("/contacts").contentType(MediaType.APPLICATION_FORM_URLENCODED)
+                        .param("name", "").param("email", "[email protected]").param("role", "Tester"))
+                .andExpect(status().isUnprocessableContent()).andReturn();
+        assertThat(plain.getResponse().getContentAsString()).contains("<!DOCTYPE html>", "Name is required");
+
+        new Transcript("05-create-validation-errors.txt")
+                .exchange("curl -H 'HX-Request: true' -d 'name=&email=not-an-email&role=Developer' /contacts", hx)
+                .exchange("curl -d 'name=&[email protected]&role=Tester' /contacts   (no JavaScript, no HX header)", plain)
+                .write();
+    }
+
+    @Test
+    void duplicateEmailIsAFieldError() throws Exception {
+        MvcResult r = mvc.perform(post("/contacts").header("HX-Request", "true")
+                        .param("name", "Someone").param("email", "[email protected]").param("role", "Tester"))
+                .andExpect(status().isUnprocessableContent()).andReturn();
+        assertThat(r.getResponse().getContentAsString()).contains("That email is already in the list");
+        assertThat(repo.count()).isEqualTo(23);
+    }
+
+    @Test
+    void validCreateRedirects() throws Exception {
+        MvcResult hx = mvc.perform(post("/contacts").header("HX-Request", "true")
+                        .param("name", "Zoya Khan").param("email", "[email protected]").param("role", "Developer"))
+                .andExpect(status().isOk()).andReturn();
+        assertThat(hx.getResponse().getHeader("HX-Redirect")).isEqualTo("/contacts");
+        assertThat(hx.getResponse().getContentAsString()).isEmpty();
+        assertThat(repo.count()).isEqualTo(24);
+
+        MvcResult plain = mvc.perform(post("/contacts")
+                        .param("name", "Zubin Irani").param("email", "[email protected]").param("role", "Tester"))
+                .andExpect(status().isFound()).andReturn();
+        assertThat(plain.getResponse().getHeader("Location")).isEqualTo("/contacts");
+        assertThat(repo.count()).isEqualTo(25);
+
+        new Transcript("06-create-success.txt")
+                .exchange("curl -H 'HX-Request: true' -d 'name=Zoya Khan&[email protected]&role=Developer' /contacts", hx, HEADERS)
+                .exchange("curl -d 'name=Zubin Irani&[email protected]&role=Tester' /contacts", plain, HEADERS)
+                .write();
+    }
+
+    // ---- 4. inline edit ----------------------------------------------------------------
+
+    @Test
+    void inlineEditCycle() throws Exception {
+        Long id = repo.findAll().stream().filter(c -> c.getName().equals("Aarav Kulkarni")).findFirst().orElseThrow().getId();
+
+        MvcResult edit = mvc.perform(get("/contacts/" + id + "/edit").header("HX-Request", "true"))
+                .andExpect(status().isOk()).andReturn();
+        String e = edit.getResponse().getContentAsString();
+        assertThat(e).contains("class=\"editing\"", "value=\"Aarav Kulkarni\"", "hx-put=\"/contacts/" + id + "\"");
+        assertThat(e).doesNotContain("<html", "<table");
+
+        MvcResult bad = mvc.perform(put("/contacts/" + id).header("HX-Request", "true")
+                        .contentType(MediaType.APPLICATION_FORM_URLENCODED)
+                        .param("name", "").param("email", "broken").param("role", "Architect"))
+                .andExpect(status().isUnprocessableContent()).andReturn();
+        assertThat(bad.getResponse().getContentAsString()).contains("class=\"editing\"", "Name is required", "Email must look like");
+        assertThat(repo.findById(id).orElseThrow().getName()).isEqualTo("Aarav Kulkarni"); // unchanged
+
+        MvcResult ok = mvc.perform(put("/contacts/" + id).header("HX-Request", "true")
+                        .contentType(MediaType.APPLICATION_FORM_URLENCODED)
+                        .param("name", "Aarav K.").param("email", "[email protected]").param("role", "Architect"))
+                .andExpect(status().isOk()).andReturn();
+        String o = ok.getResponse().getContentAsString();
+        assertThat(o).contains("<td>Aarav K.</td>").doesNotContain("class=\"editing\"");
+        assertThat(repo.findById(id).orElseThrow().getEmail()).isEqualTo("[email protected]");
+
+        MvcResult cancel = mvc.perform(get("/contacts/" + id).header("HX-Request", "true")).andReturn();
+        assertThat(cancel.getResponse().getContentAsString()).contains("<td>Aarav K.</td>");
+
+        new Transcript("07-inline-edit.txt")
+                .exchange("curl -H 'HX-Request: true' /contacts/" + id + "/edit        (Edit button)", edit)
+                .exchange("curl -X PUT -H 'HX-Request: true' -d 'name=&email=broken&role=Architect' /contacts/" + id + "   (Save, invalid)", bad)
+                .exchange("curl -X PUT -H 'HX-Request: true' -d 'name=Aarav K.&[email protected]&role=Architect' /contacts/" + id + "   (Save, valid)", ok)
+                .write();
+    }
+
+    // ---- 5. delete ---------------------------------------------------------------------
+
+    @Test
+    void deleteReturns200NotNoContent() throws Exception {
+        Long id = repo.findAll().get(0).getId();
+        MvcResult r = mvc.perform(delete("/contacts/" + id).header("HX-Request", "true")).andReturn();
+        assertThat(r.getResponse().getStatus()).isEqualTo(200);               // 204 would not be swapped
+        assertThat(r.getResponse().getContentAsString()).isEmpty();
+        assertThat(r.getResponse().getHeader("HX-Trigger")).isEqualTo("contactsChanged");
+        assertThat(repo.existsById(id)).isFalse();
+
+        MvcResult missing = mvc.perform(delete("/contacts/999999").header("HX-Request", "true")).andReturn();
+        assertThat(missing.getResponse().getStatus()).isEqualTo(404);
+
+        new Transcript("08-delete.txt")
+                .exchange("curl -X DELETE -H 'HX-Request: true' /contacts/" + id, r, HEADERS)
+                .exchange("curl -X DELETE -H 'HX-Request: true' /contacts/999999", missing, HEADERS)
+                .write();
+    }
+
+    @Test
+    void deletingTheLastRowOfTheLastPageClampsThePager() throws Exception {
+        // 23 contacts, 5 per page: page 5 has 3. Delete all three, then reload page 5 (index 4).
+        var last = repo.findAll(org.springframework.data.domain.PageRequest.of(4, 5,
+                org.springframework.data.domain.Sort.by("name").and(org.springframework.data.domain.Sort.by("id")))).getContent();
+        assertThat(last).hasSize(3);
+        for (Contact c : last) mvc.perform(delete("/contacts/" + c.getId()).header("HX-Request", "true"));
+        MvcResult r = mvc.perform(get("/contacts?page=4").header("HX-Request", "true")).andReturn();
+        String body = r.getResponse().getContentAsString();
+        assertThat(body).contains("Page 4 of 4 (20 contacts)");
+        new Transcript("09-delete-last-page-clamps.txt")
+                .note("deleted the 3 rows on page 5, then the table (which re-fetches page 5 after HX-Trigger) asks for page index 4")
+                .exchange("curl -H 'HX-Request: true' '/contacts?page=4'", r)
+                .write();
+    }
+}

thymeleaf-htmx/src/test/java/com/ankurm/thymeleafhtmx/Transcript.java

@@ -0,0 +1,50 @@
+package com.ankurm.thymeleafhtmx;
+
+import org.springframework.test.web.servlet.MvcResult;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.ArrayList;
+import java.util.List;
+
+/** Writes what a request really returned to output/NN-name.txt. Every console block in the
+ *  article is quoted from one of these files, and the test that wrote it asserts on the same data. */
+final class Transcript {
+
+    private final StringBuilder sb = new StringBuilder();
+    private final String file;
+
+    Transcript(String file) {
+        this.file = file;
+    }
+
+    /** Request line, the headers we care about, then the body exactly as returned. */
+    Transcript exchange(String request, MvcResult r, String... headerNames) throws Exception {
+        sb.append("# request (curl notation, sent through MockMvc): ").append(request).append('\n');
+        sb.append("HTTP ").append(r.getResponse().getStatus()).append('\n');
+        List<String> names = new ArrayList<>(List.of(headerNames));
+        for (String h : names) {
+            for (String v : r.getResponse().getHeaders(h)) {
+                sb.append(h).append(": ").append(v).append('\n');
+            }
+        }
+        String body = r.getResponse().getContentAsString();
+        sb.append("---- body (").append(body.length()).append(" chars) ----\n");
+        sb.append(body);
+        if (!body.endsWith("\n")) sb.append('\n');
+        sb.append('\n');
+        return this;
+    }
+
+    Transcript note(String text) {
+        sb.append("# ").append(text).append('\n');
+        return this;
+    }
+
+    void write() throws IOException {
+        Path out = Path.of("output", file);
+        Files.createDirectories(out.getParent());
+        Files.writeString(out, sb.toString());
+    }
+}