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/src/broken/UsesRestTemplate.java

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+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

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+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

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+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

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+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

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+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

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+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

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+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

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+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

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+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

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+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);
+		}
+	}
+}