Annotation Stripper

Core classes and Gradle plugin to strip requested annotations from compiled classes.

Originally build to hide Jakarta EE annotations from Java 8 (see Motivation / Background).

Gradle plugin / Kotlin DSL

plugins {
  `java-library`
  id("org.projectnessie.annotation-stripper") version "0.1.2"
}

dependencies {
  compileOnly("javax.ws.rs:javax.ws.rs-api:2.1.1")
  compileOnly("jakarta.ws.rs:jakarta.ws.rs-api:3.1.0")
}

annotationStripper {
  // registerDefault() registers annotation stripping on the "main" source set.
  registerDefault().configure {
    // Drop all annotations in the jakarta.* "namespace"
    annotationsToDrop("^jakarta[.].+".toRegex())
    // but keep the annotation for Java 11 and newer.
    unmodifiedClassesForJavaVersion.set(11)
    // The resulting class files (that end in the jar for this sample project) contains classes
    // without the jakarta.* annotations for Java 8, but keeps both javax.* and jakarta.*
    // annotations for Java 11 and newer by effectively producing a multi-release jar.
  }
}

Gradle plugin / Groovy DSL

plugins {
  id 'java-library'
  id 'org.projectnessie.annotation-stripper' version '0.1.2'
}

dependencies {
  compileOnly 'javax.ws.rs:javax.ws.rs-api:2.1.1'
  compileOnly 'jakarta.ws.rs:jakarta.ws.rs-api:3.1.0'
}

annotationStripper {
  // registerDefault() registers annotation stripping on the "main" source set.
  registerDefault().configure {
    // Drop all annotations in the jakarta.* "namespace"
    annotationsToDrop(~'^jakarta[.].+')
    // but keep the annotation for Java 11 and newer.
    unmodifiedClassesForJavaVersion.set(11)
    // The resulting class files (that end in the jar for this sample project) contains classes
    // without the jakarta.* annotations for Java 8, but keeps both javax.* and jakarta.*
    // annotations for Java 11 and newer by effectively producing a multi-release jar.
  }
}

Maven plugin

Not there - contributions are welcome!

Motivation / Background

This plugin originates from an effort to work around the old bug JDK-8152174, which was fixed in July 2016 for Java 9, but was never back-ported to Java 8.

Today, with Jakarta EE APIs being built for Java 11+ and the javax.->jakarta. rename, and our mandate to support Nessie clients with Java 8 and Java 11 or newer, while the Nessie Quarkus servers run on Java 11 or newer, the most viable solution was to "duplicate" the javax.* annotations with their jakarta.* counterparts.

For example a REST class like this

import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;

@Path("/hello")
class FooResource {
  @GET
  String helloWorld(@PathParam String echoMe) {
    return echoMe;
  }
} 

became

import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;

@Path("/hello")
@jakarta.ws.rs.Path("/path")
class FooResource {
  @GET
  @jakarta.ws.rs.GET
  String helloWorld(@PathParam @jakarta.ws.rs.PathParam("meep") String echoMe) {
    return echoMe;
  }
} 

The approach looks^Hed very promising, it relies on the Java specification, which says that annotations that are not present must be ignored (aka cannot be inspected via reflection). So old clients (but also servers) that use Java EE (aka javax.* annotations) work, but also Jakarta EE clients and servers work, for example Quarkus 3 or newer.

And it does! Until the code is run on even the newest Java 8, because of JDK-8152174.