Three new article modules: configuration binding, profiles and config data, Spring AOP

configuration-properties/ @ConfigurationProperties vs @Value on Spring Boot 4.1.1. The relaxed-binding matrix is generated by binding each spelling rather than transcribed, and re-checked against real processes -- the in-process probe was wrong twice before it was right. Records the three findings that came out of it: @Value does get relaxed resolution inside Spring Boot (Boot attaches ConfigurationPropertySources), the configuration processor silently stops generating metadata on JDK 23+ when declared as a plain dependency, and @Valid is not what makes nested constraints run. profiles-and-config/ Precedence, profiles, spring.config.import and config trees. /precedence reports every source holding a property in rank order with file and line, which turns "my profile file had no effect" into a two-line answer. Also pins the counterintuitive one: an imported file outranks the file that imported it. spring-aop/ Designators, proxy types, and aspects that do not fire. One advice per supported designator so the reference table is generated from real matches; all fourteen unsupported designators fed to the parser. Two corrections to the reference documentation: unsupported designators throw UnsupportedPointcutPrimitiveException (extends RuntimeException, not IllegalArgumentException), and spring-boot-starter-aop was renamed to spring-boot-starter-aspectj in Boot 4. 19 contract tests across the three modules, 15 captured transcripts, all regenerated by scripts/run-all.sh. Verified on Spring Boot 4.1.1, Spring Framework 7.0.9, JDK 25.0.4.1. Co-Authored-By: Claude Opus 5 <[email protected]> Claude-Session: https://claude.ai/code/session_01Gip4srpzMwjgoba6uEfbr5
2026-09-08 16:47:48 +00:00
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+package com.ankurm.profiles;
+
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.WebApplicationType;
+import org.springframework.context.ConfigurableApplicationContext;
+import org.springframework.core.env.ConfigurableEnvironment;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Pins the precedence claims the article makes, so a future Spring Boot upgrade that changes
+ * any of them fails the build rather than quietly making the article wrong.
+ */
+class PrecedenceContractTests {
+
+    private ConfigurableApplicationContext run(String... args) {
+        SpringApplication application = new SpringApplication(ProfilesApplication.class);
+        application.setWebApplicationType(WebApplicationType.NONE);
+        return application.run(args);
+    }
+
+    @Test
+    @DisplayName("a profile-specific file beats application.yaml")
+    void profileFileBeatsBaseFile() {
+        try (var context = run("--spring.profiles.active=prod")) {
+            assertThat(context.getEnvironment().getProperty("demo.greeting"))
+                    .isEqualTo("from-application-prod-yaml");
+        }
+    }
+
+    @Test
+    @DisplayName("a profile group activates every profile it names")
+    void profileGroupExpands() {
+        try (var context = run("--spring.profiles.active=prod")) {
+            assertThat(context.getEnvironment().getActiveProfiles())
+                    .containsExactlyInAnyOrder("prod", "prod-db", "prod-metrics");
+            assertThat(context.getEnvironment().getProperty("demo.pool-size")).isEqualTo("40");
+        }
+    }
+
+    @Test
+    @DisplayName("a command-line argument beats every config file")
+    void commandLineBeatsConfigData() {
+        try (var context = run("--spring.profiles.active=prod",
+                "--demo.greeting=from-command-line")) {
+            assertThat(context.getEnvironment().getProperty("demo.greeting"))
+                    .isEqualTo("from-command-line");
+        }
+    }
+
+    /**
+     * The counterintuitive one, and the reason the article has a callout about it: an
+     * imported document outranks the document that imported it.
+     */
+    @Test
+    @DisplayName("spring.config.import: the IMPORTED file wins over the importing file")
+    void importedFileWins() {
+        try (var context = run("--spring.profiles.active=import")) {
+            ConfigurableEnvironment environment = context.getEnvironment();
+            assertThat(environment.getProperty("demo.imported-only"))
+                    .as("the import was processed at all")
+                    .isEqualTo("yes-this-file-was-read");
+            assertThat(environment.getProperty("demo.greeting"))
+                    .as("and it beat application-import.yaml, which declared the import")
+                    .isEqualTo("from-imported-yaml");
+        }
+    }
+
+    @Test
+    @DisplayName("later documents in a multi-document file win over earlier ones")
+    void multiDocumentOrdering() {
+        try (var context = run("--spring.profiles.active=multidoc")) {
+            assertThat(context.getEnvironment().getProperty("demo.greeting"))
+                    .isEqualTo("from-multidoc-default-document");
+        }
+        try (var context = run("--spring.profiles.active=multidoc,staging")) {
+            assertThat(context.getEnvironment().getProperty("demo.greeting"))
+                    .isEqualTo("from-multidoc-staging-document");
+        }
+    }
+
+    @Test
+    @DisplayName("a config tree beats application.yaml but still loses to nothing above it")
+    void configTreeIsConfigData(@org.junit.jupiter.api.io.TempDir java.nio.file.Path mount)
+            throws Exception {
+        java.nio.file.Files.writeString(mount.resolve("demo.greeting"), "from-config-tree");
+
+        try (var context = run("--spring.config.import=configtree:" + mount + "/")) {
+            assertThat(context.getEnvironment().getProperty("demo.greeting"))
+                    .isEqualTo("from-config-tree");
+        }
+        // A command-line argument still outranks it: a config tree is config data.
+        try (var context = run("--spring.config.import=configtree:" + mount + "/",
+                "--demo.greeting=from-command-line")) {
+            assertThat(context.getEnvironment().getProperty("demo.greeting"))
+                    .isEqualTo("from-command-line");
+        }
+    }
+}