Make JDK 17 the minimum Java version

[greggdonovan]

• Update lib/java/build.gradle to require JDK 17 minimum
• Update lib/java/gradle/sourceConfiguration.gradle to target Java 17
• Update contrib/thrift-maven-plugin/pom.xml to use Java 17
• Update .github/workflows/build.yml cross-test to use JDK 17
• Update lib/kotlin/*.gradle.kts files to target JVM 17
• Add Jdk17Test.java to verify JDK 17 runtime features
• Apply JDK 17 features:
  • Pattern matching for instanceof in TBaseHelper, TUnion
  • Switch expressions in TBinaryProtocol, TCompactProtocol, TJSONProtocol

https://claude.ai/code/session_01EQ812qEBnt14Gq7gKCriiS

[greptile-apps]

Greptile Overview

Greptile Summary

This PR updates the Java, Kotlin, Maven, and CI build configurations to require JDK 17 (toolchains/--release 17), removes the legacy Java Option type/test coverage, and applies Java 17 language features (pattern matching for instanceof, switch expressions) in core protocol and helper classes. It also adds package-info.java NullMarked annotations across the Java library and introduces a Jdk17Test to assert JDK 17 runtime behavior.

Overall, the changes align the build + published metadata with a Java 17 baseline across Gradle/Maven/CI and modernize runtime code paths accordingly.

Confidence Score: 3/5

• This PR is close to safe to merge, but has at least one concrete runtime-nullness bug to address first.
• Most changes are build/toolchain alignment and Java-17 syntax updates. However, TUnion.toString() can now throw an NPE given the newly annotated nullable value, and there is an unresolved question about Kotlin cross-test server JVM target consistency.
• lib/java/src/main/java/org/apache/thrift/TUnion.java; verify Kotlin cross-test server module configuration if present

Important Files Changed

Filename	Overview
.github/workflows/build.yml	Updates CI to use JDK 17 in cross-tests and bumps Gradle wrapper version/hash.
compiler/cpp/src/thrift/generate/t_java_generator.cc	Simplifies generator options and defaults to Jakarta annotations; generates NullMarked package-info with fully-qualified JSpecify annotations (style inconsistency but compiles).
contrib/thrift-maven-plugin/pom.xml	Ensures Maven plugin compiles with Java 17 compiler properties.
lib/java/build.gradle	Adds/updates JDK 17 minimum enforcement and aligns Gradle build with toolchain/release settings.
lib/java/gradle/sourceConfiguration.gradle	Targets Java 17 using toolchains and options.release = 17 for consistent bytecode.
lib/java/src/main/java/org/apache/thrift/TUnion.java	Applies instanceof pattern matching and @nullable annotations; introduces possible NPE in toString() when value is null.
lib/kotlin/build.gradle.kts	Updates Kotlin library build to use Java toolchain 17 and Kotlin JVM target 17.
lib/kotlin/cross-test-client/build.gradle.kts	Updates Kotlin cross-test client to target JVM 17 and align with Java 17 toolchain.

Sequence Diagram

sequenceDiagram
  participant Dev as Developer/CI
  participant GHA as GitHub Actions
  participant Gradle as Gradle (Java/Kotlin)
  participant Maven as Maven (plugin)
  participant Thrift as Thrift Java runtime

  Dev->>GHA: push PR (require JDK 17)
  GHA->>GHA: setup-java (17)
  GHA->>Gradle: build/test (toolchain=17, --release 17)
  Gradle->>Thrift: compile Java sources (Java 17 features)
  Gradle->>Thrift: run tests (incl. Jdk17Test)
  GHA->>Maven: build thrift-maven-plugin (source/target 17)
  Maven-->>GHA: artifact built
  Gradle-->>GHA: build/test results

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[greptile-apps]

_{8 files reviewed, 2 comments}

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[greptile-apps]

Additional Comments (2)

lib/java/src/main/java/org/apache/thrift/TUnion.java
Null dereference in toString
getFieldValue() is now annotated @Nullable, but toString() still does sb.append(v.toString()) when v is not a ByteBuffer. If a union instance has setField_ != null while value_ is null (possible via subclasses/serialization bugs), this will throw an NPE. Consider handling null explicitly (e.g., append "null" or guard before deref).

Prompt To Fix With AI

This is a comment left during a code review.
Path: lib/java/src/main/java/org/apache/thrift/TUnion.java
Line: 200:203

Comment:
**Null dereference in toString**
`getFieldValue()` is now annotated `@Nullable`, but `toString()` still does `sb.append(v.toString())` when `v` is not a `ByteBuffer`. If a union instance has `setField_ != null` while `value_` is null (possible via subclasses/serialization bugs), this will throw an NPE. Consider handling null explicitly (e.g., append `"null"` or guard before deref).

How can I resolve this? If you propose a fix, please make it concise.

---

lib/kotlin/cross-test-client/build.gradle.kts
JDK 17 enforcement gap
This PR updates Kotlin builds to target JVM 17, but only cross-test-client is changed. If lib/kotlin/cross-test-server/build.gradle.kts exists in this repo, it likely still targets an older JVM and will produce mismatched bytecode in cross-tests. Please ensure the server module is updated to the same Java/Kotlin jvmTarget=17 / toolchain settings (or confirm it’s intentionally absent). Is there a lib/kotlin/cross-test-server module in this repository? If so, can you update it to match the client’s JVM 17/toolchain settings?

Prompt To Fix With AI

This is a comment left during a code review.
Path: lib/kotlin/cross-test-client/build.gradle.kts
Line: 1:3

Comment:
**JDK 17 enforcement gap**
This PR updates Kotlin builds to target JVM 17, but only `cross-test-client` is changed. If `lib/kotlin/cross-test-server/build.gradle.kts` exists in this repo, it likely still targets an older JVM and will produce mismatched bytecode in cross-tests. Please ensure the server module is updated to the same Java/Kotlin `jvmTarget=17` / toolchain settings (or confirm it’s intentionally absent). Is there a `lib/kotlin/cross-test-server` module in this repository? If so, can you update it to match the client’s JVM 17/toolchain settings?

How can I resolve this? If you propose a fix, please make it concise.