Add boot42-preview module: Spring Boot 4.2.0-M2 vs 4.1.1 forwarded headers, AMQP starters, buildpack cache, RestTemplate removal warnings

Co-Authored-By: Claude Sonnet 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01Gth99spB1CzQmBFofXmU4Z

boot42-preview/README.md

@@ -0,0 +1,16 @@
+# boot42-preview
+
+Companion module for the ankurm.com article *Spring Boot 4.2 Preview: AMQP 1.0, Buildpack Image Cache and What to Test Now*.
+Everything runs against **4.2.0-M2** (a milestone, not GA) and, where a comparison matters, against **4.1.1** (GA).
+
+| Path | What it is |
+|---|---|
+| `pom.xml` / `pom-41.xml` | the same project on 4.2.0-M2 and on 4.1.1 (a `${revision}` parent does not resolve from a repository, hence two files) |
+| `src/test/.../ForwardedHeadersTest` | what the container believes under each forwarded-header strategy |
+| `src/test/.../BindingOrderTest` | Set and Map iteration order from a properties file |
+| `src/broken/UsesRestTemplate.java` | not built; compiled by the facts script to capture the deprecation warnings |
+| `src/main/.../RestClientReplacement` | the replacement, compiled clean |
+| `examples/build-image-cache-fragment.xml` | **not executed** (needs Docker and a registry) |
+| `output/` | every transcript quoted in the article; `./scripts/run-all.sh` regenerates them |
+
+There is deliberately no `docs/` folder: the explanations live in the article.

boot42-preview/examples/build-image-cache-fragment.xml

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+<!-- NOT EXECUTED: needs a Docker daemon and a registry. Element names come from the setters javap shows in
+     output/04-buildpack-cache-classes.txt (CacheInfo.setImage, ImageCacheInfo.setName). -->
+<plugin>
+  <groupId>org.springframework.boot</groupId>
+  <artifactId>spring-boot-maven-plugin</artifactId>
+  <configuration>
+    <image>
+      <buildCache>
+        <image>
+          <name>registry.example.com/team/demo-build-cache:latest</name>
+        </image>
+      </buildCache>
+    </image>
+  </configuration>
+</plugin>

boot42-preview/output/01-forwarded-headers-on-4.1.1.txt

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+# 01-forwarded-headers  (Spring Boot 4.1.1, JDK 25)
+none/x-forwarded       scheme=http secure=false host=localhost port=<random>
+none/rfc7239           scheme=http secure=false host=localhost port=<random>
+native/x-forwarded     scheme=https secure=true host=shop.example.com port=443
+native/rfc7239         scheme=http secure=false host=localhost port=<random>
+framework/x-forwarded  scheme=https secure=true host=shop.example.com port=443
+framework/rfc7239      scheme=https secure=true host=shop.example.com port=443
+framework+standard/x-forwarded scheme=https secure=true host=shop.example.com port=443
+framework+standard/rfc7239 scheme=https secure=true host=shop.example.com port=443
+header-format=forwarded -> started (property ignored)

boot42-preview/output/01-forwarded-headers.txt

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+# 01-forwarded-headers  (Spring Boot 4.2.0-M2, JDK 25)
+none/x-forwarded       scheme=http secure=false host=localhost port=<random>
+none/rfc7239           scheme=http secure=false host=localhost port=<random>
+native/x-forwarded     scheme=https secure=true host=shop.example.com port=443
+native/rfc7239         scheme=http secure=false host=localhost port=<random>
+framework/x-forwarded  scheme=https secure=true host=shop.example.com port=443
+framework/rfc7239      scheme=http secure=false host=localhost port=<random>
+framework+standard/x-forwarded scheme=http secure=false host=localhost port=<random>
+framework+standard/rfc7239 scheme=https secure=true host=shop.example.com port=443
+header-format=forwarded -> IllegalArgumentException: No enum constant org.springframework.boot.webmvc.autoconfigure.WebMvcProperties.HeaderFormat.forwarded

boot42-preview/output/02-set-and-map-binding-order-on-4.1.1.txt

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+# 02-set-and-map-binding-order  (Spring Boot 4.1.1, JDK 25)
+file order    : zulu, alpha, mike, bravo, yankee, charlie
+Set class     : java.util.LinkedHashSet
+Set order     : [zulu, alpha, mike, bravo, yankee, charlie]
+Map class     : java.util.LinkedHashMap
+Map key order : [zulu, alpha, mike, bravo, yankee, charlie]

boot42-preview/output/02-set-and-map-binding-order.txt

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+# 02-set-and-map-binding-order  (Spring Boot 4.2.0-M2, JDK 25)
+file order    : zulu, alpha, mike, bravo, yankee, charlie
+Set class     : java.util.LinkedHashSet
+Set order     : [zulu, alpha, mike, bravo, yankee, charlie]
+Map class     : java.util.LinkedHashMap
+Map key order : [zulu, alpha, mike, bravo, yankee, charlie]

boot42-preview/output/03-amqp-starters.txt

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+# 03-amqp-starters (POM descriptions and contents straight from Maven Central)
+spring-boot-starter-amqp           4.1.1      HTTP 200  "Starter for using Spring AMQP and Rabbit MQ"  -> spring-boot-amqp
+spring-boot-starter-amqp           4.2.0-M2   HTTP 200  "Starter for generic AMQP 1.0 support"  -> spring-boot-amqp
+spring-boot-starter-rabbitmq       4.1.1      HTTP 404  (does not exist)
+spring-boot-starter-rabbitmq       4.2.0-M2   HTTP 200  "Starter for using RabbitMQ messaging and streaming broker"  -> spring-boot-rabbitmq
+spring-boot-starter-amqp-rabbitmq  4.1.1      HTTP 404  (does not exist)
+spring-boot-starter-amqp-rabbitmq  4.2.0-M2   HTTP 200  "Starter for using Spring AMQP with Rabbit MQ over AMQP 1.0 protocol"  -> spring-boot-amqp-rabbitmq
+
+# auto-configuration each module registers (AutoConfiguration.imports)
+--- spring-boot-amqp 4.1.1
+  org.springframework.boot.amqp.autoconfigure.RabbitAutoConfiguration
+  org.springframework.boot.amqp.autoconfigure.health.RabbitHealthContributorAutoConfiguration
+  org.springframework.boot.amqp.autoconfigure.metrics.RabbitMetricsAutoConfiguration
+--- spring-boot-amqp 4.2.0-M2
+  org.springframework.boot.amqp.autoconfigure.AmqpAutoConfiguration
+
+--- spring-boot-rabbitmq 4.2.0-M2
+  org.springframework.boot.rabbitmq.autoconfigure.RabbitAutoConfiguration
+  org.springframework.boot.rabbitmq.autoconfigure.health.RabbitHealthContributorAutoConfiguration
+  org.springframework.boot.rabbitmq.autoconfigure.metrics.RabbitMetricsAutoConfiguration
+--- spring-boot-amqp-rabbitmq 4.2.0-M2
+  org.springframework.boot.amqp.rabbitmq.autoconfigure.AmqpRabbitAutoConfiguration
+  org.springframework.boot.amqp.rabbitmq.autoconfigure.health.AmqpRabbitHealthContributorAutoConfiguration
+

boot42-preview/output/04-buildpack-cache-classes.txt

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+# 04-buildpack-cache-classes (javap, spring-boot-buildpack-platform and spring-boot-maven-plugin)
+--- buildpack-platform 4.1.1: classes matching Cache
+  Cache$Bind.class
+  Cache$Format.class
+  Cache$Volume.class
+  Cache.class
+--- buildpack-platform 4.2.0-M2: classes matching Cache
+  Cache.class
+  ImageCache.class
+  LocalCache$Bind.class
+  LocalCache$Volume.class
+  LocalCache.class
+--- javap Cache (4.2.0-M2)
+Compiled from "Cache.java"
+public interface Cache {
+  public default LocalCache$Volume getVolume();
+  public default LocalCache$Bind getBind();
+  public default ImageCache getImage();
+  public static LocalCache volume(java.lang.String);
+  public static LocalCache volume(VolumeName);
+  public static LocalCache bind(java.lang.String);
+  public static ImageCache image(java.lang.String);
+}
+--- javap org.springframework.boot.maven.CacheInfo (4.2.0-M2)
+Compiled from "CacheInfo.java"
+public class CacheInfo {
+  public CacheInfo();
+  public void setVolume(LocalCacheInfo$VolumeCacheInfo);
+  public void setBind(LocalCacheInfo$BindCacheInfo);
+  public void setImage(CacheInfo$ImageCacheInfo);
+  Cache asCache();
+  static CacheInfo fromVolume(LocalCacheInfo$VolumeCacheInfo);
+  static CacheInfo fromBind(LocalCacheInfo$BindCacheInfo);
+  static CacheInfo fromImage(CacheInfo$ImageCacheInfo);
+}
+--- javap org.springframework.boot.maven.LocalCacheInfo (4.2.0-M2)
+Compiled from "LocalCacheInfo.java"
+public class LocalCacheInfo {
+  public LocalCacheInfo();
+  LocalCacheInfo(LocalCache);
+  public void setVolume(LocalCacheInfo$VolumeCacheInfo);
+  public void setBind(LocalCacheInfo$BindCacheInfo);
+  LocalCache asCache();
+  static LocalCacheInfo fromVolume(LocalCacheInfo$VolumeCacheInfo);
+  static LocalCacheInfo fromBind(LocalCacheInfo$BindCacheInfo);
+}
+--- javap -p Image, fields mentioning cache/workspace (4.2.0-M2)
+  LocalCacheInfo buildWorkspace;
+  CacheInfo buildCache;
+  LocalCacheInfo launchCache;

boot42-preview/output/05-resttemplate-deprecations.txt

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+# 05-resttemplate-deprecations (javac -Xlint:deprecation on src/broken/UsesRestTemplate.java)
+--- Spring Boot 4.1.1
+--- Spring Boot 4.2.0-M2
+UsesRestTemplate.java:8: warning: [removal] RestTemplate in org.springframework.web.client has been deprecated and marked for removal
+	RestTemplate viaBuilder(RestTemplateBuilder builder) {
+	^
+UsesRestTemplate.java:8: warning: [removal] RestTemplateBuilder in org.springframework.boot.restclient has been deprecated and marked for removal
+	RestTemplate viaBuilder(RestTemplateBuilder builder) {
+	                        ^
+UsesRestTemplate.java:12: warning: [removal] TestRestTemplate in org.springframework.boot.resttestclient has been deprecated and marked for removal
+	TestRestTemplate viaTest(TestRestTemplate t) {
+	^
+UsesRestTemplate.java:12: warning: [removal] TestRestTemplate in org.springframework.boot.resttestclient has been deprecated and marked for removal
+	TestRestTemplate viaTest(TestRestTemplate t) {
+	                         ^
+UsesRestTemplate.java:16: warning: [removal] RestTemplate in org.springframework.web.client has been deprecated and marked for removal
+	RestTemplate plain() {
+	^
+UsesRestTemplate.java:17: warning: [removal] RestTemplate in org.springframework.web.client has been deprecated and marked for removal
+		return new RestTemplate();
+		           ^
+6 warnings

boot42-preview/output/06-restclient-replacement.txt

@@ -0,0 +1,2 @@
+# 06-restclient-replacement (javac -Xlint:deprecation on the RestClient version, Spring Boot 4.2.0-M2)
+javac finished; lines above this one are warnings (none means a clean compile)

boot42-preview/pom-41.xml

@@ -0,0 +1,57 @@
+<?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>4.1.1</version>
+    <relativePath/>
+  </parent>
+
+  <groupId>com.ankurm</groupId>
+  <artifactId>boot42-preview-on-41</artifactId>
+  <version>1.0.0</version>
+  <name>boot42-preview</name>
+  <description>Spring Boot 4.2 milestone preview: what to test now, run against 4.2.0-M2 and 4.1.1</description>
+
+  <properties>
+    <java.version>25</java.version>
+    <boot.label>4.1.1</boot.label>
+  </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-restclient</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>org.springframework.boot</groupId>
+      <artifactId>spring-boot-starter-webmvc-test</artifactId>
+      <scope>test</scope>
+    </dependency>
+  </dependencies>
+
+  <build>
+    <plugins>
+      <plugin>
+        <artifactId>maven-surefire-plugin</artifactId>
+        <configuration>
+          <systemPropertyVariables>
+            <boot.label>${boot.label}</boot.label>
+          </systemPropertyVariables>
+        </configuration>
+      </plugin>
+      <plugin>
+        <groupId>org.springframework.boot</groupId>
+        <artifactId>spring-boot-maven-plugin</artifactId>
+      </plugin>
+    </plugins>
+  </build>
+</project>

boot42-preview/pom.xml

@@ -0,0 +1,57 @@
+<?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>4.2.0-M2</version>
+    <relativePath/>
+  </parent>
+
+  <groupId>com.ankurm</groupId>
+  <artifactId>boot42-preview</artifactId>
+  <version>1.0.0</version>
+  <name>boot42-preview</name>
+  <description>Spring Boot 4.2 milestone preview: what to test now, run against 4.2.0-M2 and 4.1.1</description>
+
+  <properties>
+    <java.version>25</java.version>
+    <boot.label>4.2.0-M2</boot.label>
+  </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-restclient</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>org.springframework.boot</groupId>
+      <artifactId>spring-boot-starter-webmvc-test</artifactId>
+      <scope>test</scope>
+    </dependency>
+  </dependencies>
+
+  <build>
+    <plugins>
+      <plugin>
+        <artifactId>maven-surefire-plugin</artifactId>
+        <configuration>
+          <systemPropertyVariables>
+            <boot.label>${boot.label}</boot.label>
+          </systemPropertyVariables>
+        </configuration>
+      </plugin>
+      <plugin>
+        <groupId>org.springframework.boot</groupId>
+        <artifactId>spring-boot-maven-plugin</artifactId>
+      </plugin>
+    </plugins>
+  </build>
+</project>

boot42-preview/scripts/capture-facts.sh

@@ -0,0 +1,78 @@
+#!/usr/bin/env bash
+# Facts read from jars and POMs on Maven Central: nothing here needs a running application.
+set -euo pipefail
+cd "$(dirname "$0")/.."
+M="$HOME/.m2/repository/org/springframework/boot"
+CEN=https://repo1.maven.org/maven2/org/springframework/boot
+W=$(mktemp -d)
+for v in 4.1.1 4.2.0-M2; do for a in spring-boot-maven-plugin spring-boot-buildpack-platform spring-boot-amqp spring-boot-amqp-rabbitmq spring-boot-rabbitmq; do
+  mvn -B -q dependency:get -Dartifact=org.springframework.boot:$a:$v >/dev/null 2>&1 || true
+done; done
+
+{
+  echo "# 03-amqp-starters (POM descriptions and contents straight from Maven Central)"
+  for a in spring-boot-starter-amqp spring-boot-starter-rabbitmq spring-boot-starter-amqp-rabbitmq; do
+    for v in 4.1.1 4.2.0-M2; do
+      for try in 1 2 3 4 5; do
+        code=$(curl -s -o "$W/p.xml" -w '%{http_code}' "$CEN/$a/$v/$a-$v.pom")
+        [ "$code" = 429 ] || break
+        sleep $((try * 3))
+      done
+      if [ "$code" = 200 ]; then
+        d=$(grep -m1 '<description>' "$W/p.xml" | sed 's/ *<[^>]*>//g')
+        dep=$(grep -E '<artifactId>spring-boot-(amqp|rabbitmq|amqp-rabbitmq)</artifactId>' "$W/p.xml" | sed 's/ *<[^>]*>//g' | paste -sd, -)
+        printf '%-34s %-10s HTTP %s  "%s"  -> %s\n' "$a" "$v" "$code" "$d" "$dep"
+      else
+        printf '%-34s %-10s HTTP %s  (does not exist)\n' "$a" "$v" "$code"
+      fi
+    done
+  done
+  echo
+  echo "# auto-configuration each module registers (AutoConfiguration.imports)"
+  for a in spring-boot-amqp spring-boot-rabbitmq spring-boot-amqp-rabbitmq; do
+    for v in 4.1.1 4.2.0-M2; do
+      j="$M/$a/$v/$a-$v.jar"
+      if [ -f "$j" ]; then
+        echo "--- $a $v"; unzip -p "$j" META-INF/spring/org.springframework.boot.autoconfigure.AutoConfiguration.imports 2>/dev/null | sed 's/^/  /' || true; echo
+      fi
+    done
+  done
+} > output/03-amqp-starters.txt
+
+{
+  echo "# 04-buildpack-cache-classes (javap, spring-boot-buildpack-platform and spring-boot-maven-plugin)"
+  for v in 4.1.1 4.2.0-M2; do
+    echo "--- buildpack-platform $v: classes matching Cache"
+    unzip -l "$M/spring-boot-buildpack-platform/$v/spring-boot-buildpack-platform-$v.jar" | awk '{print $4}' | grep -E 'build/.*Cache' | sed 's#.*/build/#  #'
+  done
+  mkdir -p "$W/bp"
+  unzip -q -o "$M/spring-boot-buildpack-platform/4.2.0-M2/spring-boot-buildpack-platform-4.2.0-M2.jar" 'org/springframework/boot/buildpack/platform/build/*Cache*' -d "$W/bp"
+  unzip -q -o "$M/spring-boot-maven-plugin/4.2.0-M2/spring-boot-maven-plugin-4.2.0-M2.jar" 'org/springframework/boot/maven/*' -d "$W/bp"
+  echo "--- javap Cache (4.2.0-M2)"
+  javap -cp "$W/bp" org.springframework.boot.buildpack.platform.build.Cache 2>/dev/null | sed 's/org.springframework.boot.buildpack.platform.build.//g; s/org.springframework.boot.buildpack.platform.docker.type.//g'
+  for c in 'org.springframework.boot.maven.CacheInfo' 'org.springframework.boot.maven.LocalCacheInfo'; do
+    echo "--- javap $c (4.2.0-M2)"
+    javap -cp "$W/bp" "$c" 2>/dev/null | sed 's/org.springframework.boot.maven.//g; s/org.springframework.boot.buildpack.platform.build.//g'
+  done
+  echo "--- javap -p Image, fields mentioning cache/workspace (4.2.0-M2)"
+  javap -p -cp "$W/bp" org.springframework.boot.maven.Image 2>/dev/null | grep -E '(Cache|buildWorkspace)[a-zA-Z]* [a-zA-Z]+;$' | sed 's/org.springframework.boot.maven.//g'
+} > output/04-buildpack-cache-classes.txt
+
+{
+  echo "# 05-resttemplate-deprecations (javac -Xlint:deprecation on src/broken/UsesRestTemplate.java)"
+  for pom in pom-41.xml pom.xml; do
+    mvn -B -q -f $pom dependency:build-classpath -Dmdep.outputFile="$W/cp.txt" >/dev/null 2>&1
+    label=$([ $pom = pom.xml ] && echo 4.2.0-M2 || echo 4.1.1)
+    echo "--- Spring Boot $label"
+    mkdir -p "$W/out-$label"
+    javac -Xlint:deprecation -d "$W/out-$label" -cp "$(cat "$W/cp.txt")" src/broken/UsesRestTemplate.java 2>&1 | grep -v JAVA_TOOL | sed 's#^src/broken/##' || true
+  done
+} > output/05-resttemplate-deprecations.txt
+
+{
+  echo "# 06-restclient-replacement (javac -Xlint:deprecation on the RestClient version, Spring Boot 4.2.0-M2)"
+  mvn -B -q dependency:build-classpath -Dmdep.outputFile="$W/cp.txt" >/dev/null 2>&1
+  mkdir -p "$W/out-rc"
+  javac -Xlint:deprecation -Xlint:removal -d "$W/out-rc" -cp "$(cat "$W/cp.txt")" src/main/java/com/ankurm/boot42/RestClientReplacement.java 2>&1 | grep -v JAVA_TOOL | sed 's#^src/main/java/com/ankurm/boot42/##' || true
+  echo "javac finished; lines above this one are warnings (none means a clean compile)"
+} > output/06-restclient-replacement.txt

boot42-preview/scripts/run-all.sh

@@ -0,0 +1,11 @@
+#!/usr/bin/env bash
+# Regenerates every file under output/. Needs JDK 25 and Maven 3.9 with network access to Maven Central.
+#   ./scripts/run-all.sh
+# 01-02 come from the test suite (run on 4.2.0-M2, then on 4.1.1 via pom-41.xml, which writes the *-on-4.1.1 files).
+# 03-06 come from jars, POMs and javac. Port numbers are random, so the transcripts print "<random>".
+set -euo pipefail
+cd "$(dirname "$0")/.."
+mvn -B test
+mvn -B -f pom-41.xml test
+./scripts/capture-facts.sh
+ls -1 output

boot42-preview/src/broken/UsesRestTemplate.java

@@ -0,0 +1,19 @@
+import org.springframework.boot.restclient.RestTemplateBuilder;
+import org.springframework.boot.resttestclient.TestRestTemplate;
+import org.springframework.web.client.RestTemplate;
+
+/** Not part of the build: compiled by scripts/capture-facts.sh so the compiler's own words are committed. */
+class UsesRestTemplate {
+
+	RestTemplate viaBuilder(RestTemplateBuilder builder) {
+		return builder.build();
+	}
+
+	TestRestTemplate viaTest(TestRestTemplate t) {
+		return t;
+	}
+
+	RestTemplate plain() {
+		return new RestTemplate();
+	}
+}

boot42-preview/src/main/java/com/ankurm/boot42/Boot42PreviewApplication.java

@@ -0,0 +1,9 @@
+package com.ankurm.boot42;
+
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+/** Minimal application. Every experiment in this module lives in src/test. */
+@SpringBootApplication
+@org.springframework.boot.context.properties.EnableConfigurationProperties(OrderProperties.class)
+public class Boot42PreviewApplication {
+}

boot42-preview/src/main/java/com/ankurm/boot42/OrderProperties.java

@@ -0,0 +1,10 @@
+package com.ankurm.boot42;
+
+import java.util.Map;
+import java.util.Set;
+import org.springframework.boot.context.properties.ConfigurationProperties;
+
+/** A Set and a Map bound from a file where the keys are deliberately not alphabetical. */
+@ConfigurationProperties("app")
+public record OrderProperties(Set<String> regions, Map<String, Integer> limits) {
+}

boot42-preview/src/main/java/com/ankurm/boot42/RestClientReplacement.java

@@ -0,0 +1,15 @@
+package com.ankurm.boot42;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.web.client.RestClient;
+
+/** What the deprecated RestTemplateBuilder code turns into: an injected RestClient.Builder. */
+@Configuration(proxyBeanMethods = false)
+class RestClientReplacement {
+
+	@Bean
+	RestClient inventoryClient(RestClient.Builder builder) {
+		return builder.baseUrl("http://inventory.internal").build();
+	}
+}

boot42-preview/src/main/java/com/ankurm/boot42/WhoAmIController.java

@@ -0,0 +1,23 @@
+package com.ankurm.boot42;
+
+import jakarta.servlet.http.HttpServletRequest;
+import java.util.LinkedHashMap;
+import java.util.Map;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+/** Echoes what the servlet container believes about the request, after any forwarded-header handling. */
+@RestController
+class WhoAmIController {
+
+	@GetMapping("/whoami")
+	Map<String, Object> whoAmI(HttpServletRequest request) {
+		Map<String, Object> m = new LinkedHashMap<>();
+		m.put("scheme", request.getScheme());
+		m.put("secure", request.isSecure());
+		m.put("serverName", request.getServerName());
+		m.put("serverPort", request.getServerPort());
+		m.put("remoteAddr", request.getRemoteAddr());
+		return m;
+	}
+}

boot42-preview/src/main/resources/order.properties

@@ -0,0 +1,7 @@
+app.regions=zulu,alpha,mike,bravo,yankee,charlie
+app.limits.zulu=1
+app.limits.alpha=2
+app.limits.mike=3
+app.limits.bravo=4
+app.limits.yankee=5
+app.limits.charlie=6

boot42-preview/src/test/java/com/ankurm/boot42/BindingOrderTest.java

@@ -0,0 +1,26 @@
+package com.ankurm.boot42;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.ArrayList;
+import org.junit.jupiter.api.Test;
+import org.springframework.context.ConfigurableApplicationContext;
+
+/** 4.2.0-M1: Sets and Maps bind consistently and keep the order of the configuration file. */
+class BindingOrderTest {
+
+	@Test
+	void recordsIterationOrder() {
+		Transcript t = new Transcript("02-set-and-map-binding-order");
+		try (ConfigurableApplicationContext ctx = BootRun.start("spring.config.name=order")) {
+			OrderProperties p = ctx.getBean(OrderProperties.class);
+			t.line("file order    : zulu, alpha, mike, bravo, yankee, charlie");
+			t.line("Set class     : " + p.regions().getClass().getName());
+			t.line("Set order     : " + new ArrayList<>(p.regions()));
+			t.line("Map class     : " + p.limits().getClass().getName());
+			t.line("Map key order : " + new ArrayList<>(p.limits().keySet()));
+			t.write();
+			assertThat(p.regions()).hasSize(6);
+		}
+	}
+}

boot42-preview/src/test/java/com/ankurm/boot42/BootRun.java

@@ -0,0 +1,32 @@
+package com.ankurm.boot42;
+
+import java.util.Map;
+import org.springframework.boot.WebApplicationType;
+import org.springframework.boot.builder.SpringApplicationBuilder;
+import org.springframework.context.ConfigurableApplicationContext;
+import org.springframework.core.env.Environment;
+import org.springframework.web.client.RestClient;
+
+/** Starts the real application with the given properties on a random port. */
+final class BootRun {
+
+	private BootRun() {
+	}
+
+	static ConfigurableApplicationContext start(String... props) {
+		return new SpringApplicationBuilder(Boot42PreviewApplication.class)
+				.web(WebApplicationType.SERVLET)
+				.properties(props)
+				.properties("server.port=0", "spring.main.banner-mode=off", "logging.level.root=WARN")
+				.run();
+	}
+
+	static RestClient client(ConfigurableApplicationContext ctx) {
+		Environment env = ctx.getEnvironment();
+		return RestClient.create("http://localhost:" + env.getProperty("local.server.port"));
+	}
+
+	static Map<?, ?> whoAmI(ConfigurableApplicationContext ctx, Map<String, String> headers) {
+		return client(ctx).get().uri("/whoami").headers(h -> headers.forEach(h::add)).retrieve().body(Map.class);
+	}
+}

boot42-preview/src/test/java/com/ankurm/boot42/ForwardedHeadersTest.java

@@ -0,0 +1,67 @@
+package com.ankurm.boot42;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.LinkedHashMap;
+import java.util.Map;
+import org.junit.jupiter.api.Test;
+import org.springframework.context.ConfigurableApplicationContext;
+
+/**
+ * 4.2.0-M1: "When server.forward-headers-strategy=FRAMEWORK is selected, X-Forwarded-* headers are used by
+ * default." Sends both header styles under each strategy and records what the container believes.
+ */
+class ForwardedHeadersTest {
+
+	private static final Map<String, String> X_FORWARDED = Map.of("X-Forwarded-Proto", "https",
+			"X-Forwarded-Host", "shop.example.com", "X-Forwarded-Port", "443");
+	private static final Map<String, String> RFC_7239 = Map.of("Forwarded", "proto=https;host=shop.example.com");
+
+	private static final Map<String, Map<String, String>> HEADERS = new LinkedHashMap<>();
+	static {
+		HEADERS.put("x-forwarded", X_FORWARDED);
+		HEADERS.put("rfc7239", RFC_7239);
+	}
+
+	@Test
+	void recordsBehaviourPerStrategy() {
+		Transcript t = new Transcript("01-forwarded-headers");
+		Map<String, Map<?, ?>> results = new LinkedHashMap<>();
+		for (String strategy : new String[] { "none", "native", "framework" }) {
+			for (var e : HEADERS.entrySet()) {
+				try (ConfigurableApplicationContext ctx = BootRun.start("server.forward-headers-strategy=" + strategy)) {
+					Map<?, ?> seen = BootRun.whoAmI(ctx, e.getValue());
+					String key = strategy + "/" + e.getKey();
+					results.put(key, seen);
+					t.line(String.format("%-22s scheme=%s secure=%s host=%s port=%s", key, seen.get("scheme"),
+							seen.get("secure"), seen.get("serverName"), seen.get("serverPort").toString().equals("443") ? "443" : "<random>"));
+				}
+			}
+		}
+		// the new 4.2 knob: which header family the FRAMEWORK strategy reads
+		for (var e : HEADERS.entrySet()) {
+			try (ConfigurableApplicationContext ctx = BootRun.start("server.forward-headers-strategy=framework",
+					"spring.mvc.forwarded-headers.header-format=standard")) {
+				Map<?, ?> seen = BootRun.whoAmI(ctx, e.getValue());
+				t.line(String.format("%-22s scheme=%s secure=%s host=%s port=%s", "framework+standard/" + e.getKey(),
+						seen.get("scheme"), seen.get("secure"), seen.get("serverName"), seen.get("serverPort").toString().equals("443") ? "443" : "<random>"));
+			}
+		}
+		// my first guess at the value was "forwarded"; record what the binder says about it
+		try (ConfigurableApplicationContext ctx = BootRun.start("server.forward-headers-strategy=framework",
+				"spring.mvc.forwarded-headers.header-format=forwarded")) {
+			t.line("header-format=forwarded -> started (property ignored)");
+		}
+		catch (Exception ex) {
+			Throwable root = ex;
+			while (root.getCause() != null) {
+				root = root.getCause();
+			}
+			t.line("header-format=forwarded -> " + root.getClass().getSimpleName() + ": " + root.getMessage());
+		}
+		t.write();
+		// a strategy of "none" must never trust either header
+		assertThat(results.get("none/x-forwarded").get("scheme")).isEqualTo("http");
+		assertThat(results.get("none/rfc7239").get("scheme")).isEqualTo("http");
+	}
+}

boot42-preview/src/test/java/com/ankurm/boot42/Transcript.java

@@ -0,0 +1,36 @@
+package com.ankurm.boot42;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.ArrayList;
+import java.util.List;
+
+/** Collects lines and writes output/NN-name.txt. The test asserts the same values it writes. */
+final class Transcript {
+
+	private final List<String> lines = new ArrayList<>();
+	private final Path file;
+
+	Transcript(String name) {
+		String v = System.getProperty("boot.label", "4.2.0-M2");
+		String suffix = v.equals("4.2.0-M2") ? "" : "-on-" + v;
+		this.file = Path.of("output", name + suffix + ".txt");
+		line("# " + name + "  (Spring Boot " + v + ", JDK " + Runtime.version().feature() + ")");
+	}
+
+	Transcript line(String s) {
+		lines.add(s);
+		return this;
+	}
+
+	void write() {
+		try {
+			Files.createDirectories(file.getParent());
+			Files.write(file, lines);
+		}
+		catch (IOException ex) {
+			throw new IllegalStateException(ex);
+		}
+	}
+}