Migrate from Java 8 to Java 11

[devin-ai-integration]

Summary

Migrates the project from Java 8 / Spring Boot 2.0.2 to Java 11 / Spring Boot 2.7.18. All changes validated against both Maven and Gradle builds, plus a successful application startup test.

Changes

1. Spring Boot 2.0.2 → 2.7.18 (pom.xml, build.gradle)
2. Java version 1.8 → 11 (pom.xml properties, build.gradle source/targetCompatibility)
3. Fixed H2 SQL syntax — DROP TABLE customers IF EXISTS → DROP TABLE IF EXISTS customers (required by newer H2 bundled with Spring Boot 2.7.x)
4. Removed dead cfapps.io API calls — the quoter service is offline; removed both call sites in Application.java along with unused Quote, RestTemplate, and RestTemplateBuilder imports/beans
5. Removed spring-boot-properties-migrator dependency (only needed for 1.x → 2.x migration)
6. Fixed deprecated Gradle syntax — compile/testCompile → implementation/testImplementation; baseName/version → archiveBaseName/archiveVersion
7. Synced Gradle dependencies with Maven — added spring-boot-starter-jdbc and h2 to build.gradle
8. Upgraded Gradle wrapper 4.6 → 7.6.4 (Gradle 4.6 does not support Java 11+)
9. Fixed Maven packaging — changed <packaging>pom</packaging> to <packaging>jar</packaging> so spring-boot:run and JAR generation work correctly

Validation performed

Check	Result
./mvnw dependency:resolve	Pass
./mvnw compile	Pass
./mvnw clean package	Pass
./gradlew compileJava (JAVA_HOME=java11)	Pass
./gradlew clean build bootJar (JAVA_HOME=java11)	Pass
./mvnw spring-boot:run — app startup	Pass — H2 tables created, customers inserted and queried, no exceptions

Review & Testing Checklist for Human

• Run ./mvnw spring-boot:run and verify the app starts, H2 table creation succeeds, and customer records are inserted/queried
• Run JAVA_HOME=/path/to/java11 ./gradlew clean build to confirm Gradle build (Gradle 7.6.4 requires Java 11, not 21)
• Hit http://localhost:8080/ and http://localhost:8080/topic endpoints to verify REST API works
• Verify Quote and Value model classes are still present (kept for potential future use) but no longer called at startup

Notes

• The new Object[]{"Josh"} parameter in JdbcTemplate.query() triggers a deprecation warning (deprecated in Spring 5.3+). This is cosmetic and does not affect functionality.
• Gradle builds require JAVA_HOME pointing to Java 11 since the system default may differ.
• No CI is configured for this repository.

Link to Devin session: https://app.devin.ai/sessions/541b4ffde2084f378be727ec1bf4ed2a
Requested by: @parkerduff

[devin-ai-integration]

🤖 Devin AI Engineer

I'll be helping with this pull request! Here's what you should know:

✅ I will automatically:

• Address comments on this PR. Add '(aside)' to your comment to have me ignore it.
• Look at CI failures and help fix them

Note: I can only respond to comments from users who have write access to this repository.

⚙️ Control Options:

• Disable automatic comment and CI monitoring

[devin-ai-integration]

End-to-End Test Results

Method: Started app locally via ./mvnw spring-boot:run, tested REST endpoints in browser, validated Gradle build and Java version via shell.

Migration Validation (6/6 passed)

Test	Result
App starts without exceptions (H2 tables created, customers inserted/queried)	Passed
GET / returns {"id":1,"content":"Hello, World!"}	Passed
GET /topic returns 3 topics (spring, java, javascript)	Passed
GET /datetime returns java.time output (dates, leap year, timezone)	Passed
Gradle clean build succeeds with Java 11	Passed
java -version confirms 11.0.30 runtime	Passed

Screenshots

GET / — Greeting endpoint

GET /topic — Topic list endpoint

GET /datetime — DateTime endpoint

Devin session