Add project-structure module: the same Boot 4.1 app laid out package-by-layer and package-by-feature, with the public surface counted and the javac boundary captured

Co-Authored-By: Claude Sonnet 5.5 <[email protected]> Claude-Session: https://claude.ai/code/session_01HhW8LD8r3EigoBaCGrQZx5 Co-Authored-By: Claude Sonnet 5.5 <[email protected]> Claude-Session: https://claude.ai/code/session_01HhW8LD8r3EigoBaCGrQZx5
2026-10-21 16:43:45 +00:00
parent 008211f2fa
commit ba709737de
41 changed files with 1039 additions and 0 deletions
@@ -0,0 +1,95 @@
+package com.ankurm.structure;
+
+import com.ankurm.structure.scan.broken.app.BrokenApp;
+import com.ankurm.structure.scan.fixed.FixedApp;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.springframework.boot.WebApplicationType;
+import org.springframework.boot.builder.SpringApplicationBuilder;
+import org.springframework.boot.test.system.CapturedOutput;
+import org.springframework.boot.test.system.OutputCaptureExtension;
+import org.springframework.context.ConfigurableApplicationContext;
+
+import javax.tools.*;
+import java.net.URI;
+import java.net.URL;
+import java.net.URLClassLoader;
+import java.net.http.HttpClient;
+import java.net.http.HttpRequest;
+import java.net.http.HttpResponse;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/** The two ways a project layout silently breaks component scanning. */
+@ExtendWith(OutputCaptureExtension.class)
+class ScanTrapTests {
+
+    @Test
+    void appClassInTheWrongPackage() throws Exception {
+        HttpClient http = HttpClient.newHttpClient();
+        try (Transcript t = new Transcript("05-scan-starts-at-the-app-class.txt",
+                "The controller is found only if it is in or below the @SpringBootApplication class's package")) {
+            for (var c : List.of(
+                    new Object[]{"broken", BrokenApp.class, "app class in scan.broken.app, controller in scan.broken.web (a sibling)"},
+                    new Object[]{"fixed", FixedApp.class, "app class in scan.fixed, controller in scan.fixed.web (below it)"})) {
+                try (ConfigurableApplicationContext ctx = new SpringApplicationBuilder((Class<?>) c[1])
+                        .properties("server.port=0", "spring.main.banner-mode=off", "logging.level.root=WARN").run()) {
+                    String base = "http://localhost:" + ctx.getEnvironment().getProperty("local.server.port");
+                    HttpResponse<String> r = http.send(HttpRequest.newBuilder(URI.create(base + "/hello")).GET().build(),
+                            HttpResponse.BodyHandlers.ofString());
+                    t.section((String) c[2]);
+                    t.line("GET /hello -> %d", r.statusCode());
+                    t.line("HelloController registered as a bean: %s", ctx.getBeanNamesForType(Object.class).length > 0
+                            && java.util.Arrays.stream(ctx.getBeanDefinitionNames()).anyMatch(n -> n.equals("helloController")));
+                    if (c[0].equals("broken")) assertThat(r.statusCode()).isEqualTo(404);
+                    else assertThat(r.statusCode()).isEqualTo(200);
+                }
+            }
+        }
+    }
+
+    @Test
+    void appClassInTheDefaultPackage(CapturedOutput output) throws Exception {
+        String source = "import org.springframework.boot.autoconfigure.SpringBootApplication;\n"
+                + "@SpringBootApplication\n"
+                + "public class DefaultPackageApp {\n"
+                + "}\n";
+        Path out = Files.createTempDirectory("defaultpkg");
+        JavaCompiler javac = ToolProvider.getSystemJavaCompiler();
+        JavaFileObject file = new SimpleJavaFileObject(URI.create("string:///DefaultPackageApp.java"), JavaFileObject.Kind.SOURCE) {
+            @Override public CharSequence getCharContent(boolean ignore) { return source; }
+        };
+        boolean compiled = javac.getTask(null, null, null,
+                List.of("-proc:none", "-d", out.toString(), "-classpath", System.getProperty("java.class.path")), null, List.of(file)).call();
+        assertThat(compiled).isTrue();
+
+        try (Transcript t = new Transcript("06-default-package.txt", "A @SpringBootApplication class in the default package (no package statement)")) {
+            t.line("source compiled:");
+            for (String l : source.split("\n")) t.line("    %s", l);
+            t.blank();
+            Class<?> app;
+            try (URLClassLoader cl = new URLClassLoader(new URL[]{out.toUri().toURL()}, getClass().getClassLoader())) {
+                app = Class.forName("DefaultPackageApp", true, cl);
+                String result;
+                try (ConfigurableApplicationContext ctx = new SpringApplicationBuilder(app)
+                        .web(WebApplicationType.NONE).properties("spring.main.banner-mode=off").run()) {
+                    result = "context started with " + ctx.getBeanDefinitionCount() + " bean definitions";
+                } catch (Throwable e) {
+                    Throwable root = e;
+                    while (root.getCause() != null) root = root.getCause();
+                    result = "context FAILED to start: " + e.getClass().getSimpleName() + " / root cause "
+                            + root.getClass().getSimpleName() + ": " + String.valueOf(root.getMessage()).lines().findFirst().orElse("");
+                }
+                t.section("what Spring Boot logged about the default package");
+                output.getAll().lines().filter(l -> l.contains("default package") || l.contains("WARNING"))
+                        .map(l -> l.replaceFirst("^\\S+\\s+", "")).forEach(t::line);
+                t.section("result");
+                t.line(result);
+            }
+            assertThat(output.getAll()).contains("default package");
+        }
+    }
+}