Compiling classes for multi-release JAR with module-info.java

[Paul Sandoz]

It’s also possible to do this:

javac --source-path=src/main/java9 --source-path=src/main/java -implicit:none -d target/classes-java9 --release 9 $(find src/main/java9 -name "*.java”)

but that approach is fragile (it assumes the implicitly referenced source can be processed for release 8 and 9).

Separately compiling the module descriptor source is likely a better approach.

Paul.

> On 11 Feb 2017, at 09:40, Alan Bateman <Alan.Bateman at oracle.com> wrote:
> 
> On 10/02/2017 23:06, Gunnar Morling wrote:
> 
>> :
>> 
>> If I don't have a module descriptor things work fine:
>> 
>>     javac --source-path=src/main/java -d target/classes --release 8
>> $(find src/main/java -name "*.java")
>>     javac --source-path=src/main/java9 -cp target/classes -d
>> target/classes-java9 --release 9 $(find src/main/java9 -name "*.java")
>>     jar --create --file mr.jar -C target/classes . --release 9 -C
>> target/classes-java9 .
>> 
>> Specifically, the second javac call picks up the (shared) class file
>> for "Version" from the classpath by pointing to the output directory
>> of the first compilation.
>> 
>> Things fail when adding a module descriptor:
>> 
>>     --- src/main/java9/module-info.java
>>         module com.example {
>>     }
>>     ---
> It is complicated but I think the reason you are running into issues is because the second javac command is essentially compiling a module with references to types on the class path.
> 
> If you move the module-info.java to the top-level directory directory then I would expect this should work:
> 
> javac --release 8 -d target/classes src/main/java/com/example/A.java src/main/java/com/example/Version.java
> javac -d target/classes src/main/java/module-info.java
> javac -d target/classes-java9 -cp target/classes src/main/java9/com/example/A.java
> jar --create --file mr.jar -C target/classes . --release 9 -C target/classes-java9 .
> 
> Jon might have other suggestions.
> 
> -Alan