[GitHub] [cxf] reta opened a new pull request #566: CXF-8066: Support Doclet API (JDK13+)

[GitBox <gi...@apache.org>]

reta opened a new pull request #566: CXF-8066: Support Doclet API (JDK13+)
URL: https://github.com/apache/cxf/pull/566
 
 
   The problem
   ===
   Our `java2wadl` plugin uses some part of Javadoc API to extract the documentation pieces from the
   Java classes / methods / parameters. Since OpenJDK13, this API has been removed completely [2], [3]. To support JDK13 and above, we essentially have to rewrite the implementation completely. However, we would face another blocker here: how to support JDK8-11 and JDK13+ at the same time?
   
   The solution
   ===
   Use multi-release JAR. This is exactly the use case this feature has been designed for. So what it means 
   is that `java2wadl` has additional source folder `src/main/java13` with JDK13 implementation. It would be it however there is another subtle complication. 
   
   The complication 
   ===
   For multi-release JAR, the java2wadl has to be build with 2 JDKs (ideally), pre-JDK13 and JDK13, or 
   alternatively by latest JDK13 twice, once for `src/main/java` (using `--release 8`) and once for `src/main/java13` (equivalent to `--release 13`). The issue is that Javadoc-related API comes from `tools.jar`, which is not in scope of javac's `--release` flag, it really needs to be built by JDK8. As the workaround, we could used `--release 9` to mitigate this issue (since `tools.jar` was merged into JDK9+). This is not ideal (see please the next paragraph) but we get JDK13 builds back on track.
   
   The impact
   ===
   As of now, since our release jobs are using JDK8, there is no impact on release artifacts BUT `java2wadl` 
   will fail when used with JDK13+ea builds. When JDK13 is out, we could rely on toolchain plugin to build `java2wadl` with 2 JDKs (`JDK8` and `JDK13`).
   
   I think this is the first real precedent when we have to deal with large features / API removal from JDK, whereas reflection served as very well before. But this is certainly not the last one. 

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