Upgrade to Java 17 and Spring Boot 3.2.5

[devin-ai-integration]

Summary

Upgrades this project from Java 8 / Spring Boot 2.0.2.RELEASE to Java 17 / Spring Boot 3.2.5, following the migration plan in the linked Devin session.

pom.xml

• Spring Boot parent: 2.0.2.RELEASE → 3.2.5.
• java.version: 1.8 → 17.
• Removed spring-boot-properties-migrator (a 1.x → 2.x migration aid; not needed for 3.x).
• Kept spring-boot-starter-web, spring-boot-starter-jdbc, and h2 as-is — they resolve to Spring Boot 3.2.x compatible versions through the parent BOM.
• Changed <packaging> from pom to jar so Java sources are actually compiled and a runnable Spring Boot jar is produced. With pom packaging, mvn compile/mvn package skips Java compilation, so this was already broken on master.

build.gradle

• spring-boot-gradle-plugin: 2.0.2.RELEASE → 3.2.5.
• sourceCompatibility / targetCompatibility: 1.8 → 17.
• bootJar block: baseName → archiveBaseName, version → archiveVersion (the old DSL was removed in Gradle 7+).
• Replaced deprecated configurations: compile → implementation, testCompile → testImplementation.

src/main/java/hello/Application.java

• H2 2.x SQL syntax fix: DROP TABLE customers IF EXISTS → DROP TABLE IF EXISTS customers. The legacy form was removed in H2 2.x (which is what Spring Boot 3.x bundles).
• Migrated off the deprecated JdbcTemplate.query(sql, Object[] args, RowMapper) overload to JdbcTemplate.query(sql, RowMapper, varargs...) — note the argument-order swap (RowMapper now comes before the parameter values).

gs-spring-boot.iml

• LANGUAGE_LEVEL: JDK_1_8 → JDK_17. (IDE-generated; updated for consistency.)

Maven wrapper

• Regenerated via mvn wrapper:wrapper (Maven 3.9.6, only-script distribution). Spring Boot 3.2.5 requires Maven 3.6.3+, which the previous wrapper (3.3.9) doesn't satisfy. The legacy .mvn/wrapper/maven-wrapper.jar is removed because the new only-script wrapper doesn't need it.

Not touched

No source-level javax.* → jakarta.* rename was needed — the codebase doesn't import any javax.* packages directly. Transitive javax.annotation-api / javax.validation-api are auto-replaced by Jakarta equivalents through Spring Boot 3.2.x dependency management.

Review & Testing Checklist for Human

• Confirm you're OK with the <packaging>pom</packaging> → jar change. This is required for mvn compile/mvn package to actually compile sources and was outside the original migration plan, but the repo cannot build a runnable jar without it.
• Decide whether the regenerated Maven wrapper (Maven 3.9.6, only-script distribution; .mvn/wrapper/maven-wrapper.jar removed) matches your team's wrapper conventions, or if you'd prefer a different Maven version / wrapper type.
• Run the app locally with Java 17 (./mvnw spring-boot:run) and hit the documented endpoints: GET /, /datetime, /topic, /topic/string/operation, /topic/file/operation, /topic/sort. The app does have a pre-existing call from Application.main to http://gturnquist-quoters.cfapps.io/api/random that throws UnknownHostException on networks that can't resolve that host — this is unrelated to the upgrade and existed on master.
• If you also build with Gradle: the Gradle wrapper in this repo is still pinned to Gradle 4.6, which cannot run on Java 17. You'll need to upgrade the Gradle wrapper (e.g., to 8.x) before ./gradlew clean build will succeed. Out of scope for this PR per the migration plan.
• Verify CI passes.

Test plan I ran on the box

• JAVA_HOME=/usr/lib/jvm/java-17-openjdk-amd64 ./mvnw -B clean compile → BUILD SUCCESS.
• JAVA_HOME=/usr/lib/jvm/java-17-openjdk-amd64 ./mvnw -B clean package -DskipTests → BUILD SUCCESS, produces target/gs-spring-boot-0.1.0.jar.
• java -jar target/gs-spring-boot-0.1.0.jar --server.port=8181 → Tomcat started on port 8181, Started Application in 2.359 seconds. The app then crashes from the pre-existing external RestTemplate call described above; this is not a regression.

Notes

• The repo has compiled .class files under target/classes/ checked into git (which is unusual for a Java project). I did not include the recompiled bytecode in this PR — those artifacts will be regenerated on the first Java 17 build and should not churn alongside source-level changes. Consider adding target/ to .gitignore in a follow-up.

Link to Devin session: https://app.devin.ai/sessions/e344dd76e80c4292a4e88d3a709e0e6b
Requested by: @vanessasalas-cog

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