Upgrade to Java 17 and Spring Boot 3.5.16

[devin-ai-integration]

Summary

Java 8 → 17, Spring Boot 2.0.2.RELEASE → 3.5.16 (Jakarta EE 10, Tomcat 10.1), plus build tooling that can actually run on a 17 JDK: Gradle wrapper 4.6 → 8.14.5, Maven wrapper 3.3.9 → 3.9.16. No javax.* imports existed, so the Jakarta switch is a no-op for the source.

Non-obvious bits beyond the version bumps:

• pom.xml had <packaging>pom</packaging>, so spring-boot-maven-plugin:repackage never produced a runnable artifact. Changed to jar; ./mvnw clean package now yields a bootable target/gs-spring-boot-0.1.0.jar.
• build.gradle only declared starter-web + junit while the code uses JdbcTemplate and H2, so a Gradle build of Application.java could not have compiled. Added starter-jdbc, h2, and the properties migrator so the Gradle and Maven builds are equivalent. Also compile/testCompile → implementation/testImplementation, bootJar.baseName/version → archiveBaseName/archiveVersion (removed in Gradle 8), and Java version via a toolchain rather than the sourceCompatibility project property (removed in Gradle 9).
• Two source changes were forced by Spring Framework 6, not by Java 17:
  • jdbcTemplate.query(sql, Object[] args, RowMapper) was removed in 6.0 → varargs form query(sql, rowMapper, "Josh").
  • The startup call to http://gturnquist-quoters.cfapps.io/api/random (a domain that no longer resolves) is hit twice — in main and in the CommandLineRunner bean — and under Boot 3 an exception there fails the whole application run. Both call sites now go through one logRandomQuote helper that catches RestClientException and warns instead of aborting startup.
• Deleted the stale gs-spring-boot.iml (pinned JDK_1_8 and 2.0.2 dependency versions) and gitignored *.iml, target/, build/, .gradle/; committed build output was previously tracked under target/.
• application.properties contains only a commented-out server.port, so nothing to migrate.

Verified locally on JDK 17: mvn clean package and ./gradlew build both succeed, the boot jar starts on Tomcat 10.1, GET / returns 200, GET /topic returns the topic JSON, the H2 customer insert/query runs, and the unreachable quote endpoint only logs a warning.

Link to Devin session: https://app.devin.ai/sessions/de65fc6627bf43f2b4a8d92ba9239d18
Requested by: @joebensoncog97

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[devin-ai-integration]

Runtime verification — Java 17 / Spring Boot 3.5.16 upgrade

Built and ran the boot jar on JDK 17 (openjdk 17.0.19) and exercised every controller route end-to-end.

REST API — all routes verified against the running jar

Route	Result
GET / / GET /?name=Devin	✅ {"id":4,"content":"Hello, World!"} / Hello, Devin!, counter increments
GET /topic	✅ 3 topics
POST /topic	✅ 200, kotlin appears in list
PUT /topic/kotlin	✅ 200, subjectName → Kotlin Updated
DELETE /topic/kotlin	✅ 200, list back to 3
GET /topic/minimum/length/4	✅ spring + javascript only
GET /topic/sort	✅ java, javascript, spring
GET /datetime, /topic/string/operation, /topic/file/operation	✅ all render real data

Full CRUD round trip (POST → PUT → DELETE) verified in the browser:

Startup: Tomcat 10.1.55, H2 insert/query, quote URL WARN-only

o.apache.catalina.core.StandardEngine : Starting Servlet engine: [Apache Tomcat/10.1.55]
hello.Application : Started Application in 1.14 seconds
hello.Application : WARN Unable to fetch a quote from http://gturnquist-quoters.cfapps.io/api/random: ...
hello.Application : Inserting customer record for John Woo / Jeff Dean / Josh Bloch / Josh Long
hello.Application : Querying for customer records where first_name = 'Josh':
hello.Application : Customer{id=3, firstName='Josh', lastName='Bloch'}
hello.Application : Customer{id=4, firstName='Josh', lastName='Long'}

The Josh rows confirm the new varargs JdbcTemplate.query(...) form works on Spring 6, and the unreachable quote URL only WARNs rather than failing startup.

Adversarial input — no Spring 6 migration fallout

Case	Status
POST /topic malformed JSON {bad	400 ✅
POST /topic no body	400 ✅
GET /topic/minimum/length/abc	400 ✅
GET /nope	404 ✅
GET /topic/doesnotexist	500 ⚠️

The single 500 is java.util.NoSuchElementException: No value present at TopicService.getTopicWithId (Optional.get() without a presence check) — pre-existing behaviour, unrelated to this upgrade; no javax.* or removed-API references anywhere in the trace. Worth a follow-up fix (return 404) but not a blocker for this PR.

Builds

• mvn clean package → BUILD SUCCESS, target/gs-spring-boot-0.1.0.jar (boot-repackaged) ✅
• ./gradlew clean build → BUILD SUCCESSFUL, build/libs/gs-spring-boot-0.1.0.jar ✅ (needed a Maven Central mirror init script because repo1.maven.org rate-limits the test box — environment issue, no code change made)
• ./mvnw could not be verified: downloading the 3.9.16 distribution returned HTTP 429 from repo1.maven.org on this box. The wrapper script was also non-executable in git; fixed in this PR (chmod +x mvnw).