Hi, The Lucene team was also thinking about this, and we came to the conclusion that we might need to do 2 things:
- Build a Multi-Release JAR file and only compile new classes with Java 9 there and put them into the special folder of JAR file. We plan this to make use of VarHandles on Java 9 for ByteBuffer access. You would then have the same class 2 times in JAR file, one for older versions in the default place and a replacement for Java 9+ - In addition we would have a separate compilation unit with only a single module-info.java and that’s compiled with Java 9's Javac. The resulting file could be placed in the JAR file, too (not sure where: In root or in the multi-release place??? The latter would allow us to merge this with the previous point and we would not need 3 compilation runs). We are using Apache Ant for building, so multiple invocations with javac are easy... I know that Apache Maven is also working on Multi-Release JAR files, I'd suggest to use this (if the 2nd point also works with module-info.class in the MR JAR as part of Java9 specific code). Uwe ----- Uwe Schindler uschind...@apache.org ASF Member, Apache Lucene PMC / Committer Bremen, Germany http://lucene.apache.org/ > -----Original Message----- > From: jigsaw-dev [mailto:jigsaw-dev-boun...@openjdk.java.net] On Behalf > Of Oliver Gondža > Sent: Friday, August 26, 2016 10:52 AM > To: jigsaw-dev@openjdk.java.net > Subject: Building jar targeting multiple Java versions, including 9 > > I am about to stretch support of my project from java 6, 7 and 8 to > version 9 as well. It does not work there out of the box as it accesses > sun.tools.attach.HotSpotVirtualMachine: > > ``` > class MyClass (in unnamed module @0x4d14b6c2) cannot access class > sun.tools.attach.HotSpotVirtualMachine (in module jdk.attach) because > module jdk.attach does not export sun.tools.attach to unnamed module > @0x4d14b6c2. > ``` > > Before I had a chance to experiment with introducing modules to my > application and declaring dependency on jdk.attach, my project refuses > to compile on java 9 as soon as I add module-info.java as I instruct > javac to produce java 6 bytecode (-target 1.6 -source 1.6): > > ``` > modules are not supported in -source 1.6; use -source 9 or higher to > enable modules > ``` > > How does one take advantage of modules (in this case I have no choice) > while keeping the project buildable for older Java versions? Or are > users expected not to use modules until their apps drop support for > older javas? I tried asking on SO[1] with no luck. > > [1] > http://stackoverflow.com/questions/38874646/building-modularized-java- > application-targeting-both-java-9-and-older > > Thank you > -- > oliver > Red Hat Jenkins Team
