Migrate to Java 21 / Spring Boot 3.2.5

[devin-ai-integration]

Summary

End-to-end migration of this repo from Java 8 / Spring Boot 2.0.2 to Java 21 / Spring Boot 3.2.5. Work was split across three child Devin sessions and merged onto an integration branch (devin/1777913688-java21-migration-base); this PR brings that integration branch into master.

Build configuration — Maven (child PR #20)

• pom.xml
  • Spring Boot parent: 2.0.2.RELEASE → 3.2.5
  • <java.version>: 1.8 → 21
  • Removed spring-boot-properties-migrator (1.x→2.x migration aid; not published for 3.x)
  • Other deps (spring-boot-starter-web, spring-boot-starter-jdbc, h2) inherit compatible versions from the new parent BOM
• .mvn/wrapper/maven-wrapper.properties: Maven 3.3.9 → 3.9.6 (3.9+ required for Java 21)

Build configuration — Gradle (child PR #19)

• build.gradle
  • spring-boot-gradle-plugin: 2.0.2.RELEASE → 3.2.5
  • sourceCompatibility / targetCompatibility: 1.8 → 21
  • compile(...) → implementation(...), testCompile(...) → testImplementation(...)
  • bootJar { baseName / version } → bootJar { archiveBaseName / archiveVersion }
• gradle/wrapper/gradle-wrapper.properties: Gradle 4.6 → 8.7 (8.5+ required for Java 21)

Source — Application.java (child PR #21)

• H2 2.x SQL syntax: DROP TABLE customers IF EXISTS → DROP TABLE IF EXISTS customers
• Replaced deprecated JdbcTemplate.query(sql, Object[], RowMapper) with the varargs-last query(sql, RowMapper, Object...)
• Replaced defunct http://gturnquist-quoters.cfapps.io/api/random (both occurrences) with the placeholder https://jsonplaceholder.typicode.com/posts/1. RestTemplate retained.
• Verified no javax.* imports under src/main/java/hello/ (none found, no jakarta.* rewrites needed)

Local verification under JDK 21

• ./mvnw clean package -DskipTests → BUILD SUCCESS. Maven 3.9.6 was auto-downloaded by the wrapper, the Spring Boot 3.2.5 BOM resolved cleanly, all dependencies fetched. Caveat: the pom.xml carries <packaging>pom</packaging> (pre-existing), so this phase does NOT actually compile src/main/java/hello/*.java — it just runs the lifecycle to package for a pom-typed artifact. See "Pre-existing issues" below.
• Direct javac of all 13 source files under JDK 21 against the maven-resolved classpath → succeeds (all 13 .class files produced under /tmp/javac-out). This is the strongest signal that the migration's source changes compile cleanly under Java 21 + Spring Boot 3.2.5.
• ./gradlew build (Gradle 8.7 auto-downloaded) → fails at :compileJava because org.springframework.jdbc.core.JdbcTemplate is missing on the classpath. This is pre-existing, not introduced by this migration — see below.

Pre-existing issues (NOT introduced by this migration, but worth flagging)

1. pom.xml has <packaging>pom</packaging> — wrong packaging for a Spring Boot app; ./mvnw package doesn't run maven-compiler-plugin. Out of scope per the original task spec, but a one-character follow-up (pom → jar) would make ./mvnw clean package actually compile and produce a runnable jar.
2. build.gradle is missing spring-boot-starter-jdbc and h2 dependencies — only spring-boot-starter-web is declared, so ./gradlew compileJava cannot resolve JdbcTemplate. Confirmed present on master before this PR. The Maven pom.xml has these deps, so Maven has always been the working build path for this repo.

Both are tiny pre-existing follow-ups; they do not block the Java 21 migration itself, which is verified by the direct javac compile under JDK 21.

Review & Testing Checklist for Human

• Run ./mvnw clean package under JDK 21 locally — should print BUILD SUCCESS (with the pom-packaging caveat above; see follow-up Fix build and startup: correct packaging type, handle defunct external API #1 if you want a real compile + executable jar).
• (Optional follow-up) Add spring-boot-starter-jdbc and h2 to build.gradle so ./gradlew build works as a second verification path. The fix is trivial: add implementation("org.springframework.boot:spring-boot-starter-jdbc") and runtimeOnly("com.h2database:h2"). Not in this PR because the user's task spec didn't authorize editing build.gradle beyond the four explicit bullets — happy to do it as a follow-up if desired.
• Boot the app and exercise endpoints: ./mvnw spring-boot:run (or convert packaging to jar first), then hit GET /, GET /topic, GET /datetime. Confirm Spring Boot 3.2.5 starts, the customers table loads (logs show Inserting customer record for ...), and the JdbcTemplate.query(...) for first_name = 'Josh' returns rows — that's the live exercise of both H2 2.x DROP TABLE IF EXISTS customers and the new varargs JdbcTemplate.query().
• Quote endpoint placeholder is intentional: jsonplaceholder.typicode.com/posts/1 returns {userId, id, title, body}, which won't fully populate Quote's type/value fields. The startup log line will print a Quote{type='null', value=null}. If you want real data flowing, swap to a local @RestController stub or introduce a new Post model — both out of scope for this PR.

Notes

• Child PRs that were merged into the integration branch in this PR (each scoped to a disjoint set of files; no merge conflicts):
  • Java 21 migration — Maven build config #20 — Maven build config
  • Java 21 migration — Gradle build config #19 — Gradle build config
  • Java 21 migration — Application.java source changes #21 — Application.java source changes
• No tests existed in the repo before this migration (src/test/ was absent), so there was nothing to exercise on the test path.
• Devin Review's flagged finding (Quote deserializes to all-null against the new placeholder URL) is acknowledged and intentional per the original task spec — replied in-thread on the PR.

Link to Devin session: https://app.devin.ai/sessions/e43cac2398914ee9a147ef4405dcffb3
Requested by: @dr-phil

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[devin-ai-integration]

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[devin-ai-integration]

Devin Review found 1 potential issue.

View 4 additional findings in Devin Review.

[devin-ai-integration]

🔴 New API endpoint response schema doesn't match Quote model, resulting in all-null deserialization

The API URL was changed from the old quoters service to https://jsonplaceholder.typicode.com/posts/1, but the Quote model class was not updated. The JSONPlaceholder endpoint returns {userId, id, title, body}, while Quote (src/main/java/hello/model/Quote.java:3-34) expects type (String) and value (Value), where Value (src/main/java/hello/model/Value.java:3-33) expects id (Long) and quote (String). Since Jackson's FAIL_ON_UNKNOWN_PROPERTIES defaults to false in Jackson 2.12+, the unknown fields are silently ignored and the Quote object is created with type=null and value=null. This affects both the manual RestTemplate call in main() (line 39) and the Spring-managed bean call in run() (lines 52-53), causing the application to log meaningless Quote{type='null', value=null} output instead of actual data.

Prompt for agents

The Quote and Value model classes need to be updated to match the JSONPlaceholder /posts/1 API response format. The API returns JSON like: {userId: 1, id: 1, title: "...", body: "..."}. Either: (1) create a new model class (e.g., Post) with fields userId (int), id (int), title (String), body (String), and update both getForObject calls in Application.java to use Post.class instead of Quote.class, or (2) find a different API that returns data matching the Quote/Value model structure. The affected locations are Application.java line 39 (in main()) and lines 52-53 (in the run() CommandLineRunner bean).

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[devin-ai-integration]

Acknowledged — this is intentional and matches the original task spec, which permitted "a working placeholder or mock endpoint (e.g., https://jsonplaceholder.typicode.com/posts/1 or a local stub)" precisely because the original gturnquist-quoters.cfapps.io service is permanently dead. The bot's analysis is correct that Quote will deserialize with all null fields against the JSONPlaceholder response shape.

I deliberately did NOT modify the Quote / Value model classes because:

1. The migration scope is "Java 8 → Java 21 / Spring Boot 2.0.2 → 3.2.5" — changing the domain model is out of scope.
2. Quote is only used in two startup-time RestTemplate calls that just log the result; they are not part of any user-facing flow.
3. Repointing the URL keeps the build green and the app reachable, which is the migration's actual goal. The "all-null Quote" log line is acceptable as a stub and is explicitly called out in the PR description's testing checklist (item 4).

If the team wants real data flowing through Quote again, the right follow-up is one of: (a) add a tiny local @RestController stub under src/main/java/hello/ returning a Quote-shaped JSON payload and point the RestTemplate at http://localhost:8080/..., or (b) introduce a new Post model and switch getForObject to use it. Either is a separate, non-migration change.