JavahExecutable fails on Java10

[hendriks73]

Java 10 got rid of the javah executable and replaced it with javac -h.

[hendriks73]

Looks like the regular maven compiler plugin (v3.7.0) can be configured to spit out the headers like so:

        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <configuration>
                <compilerArgs>
                    <arg>-h</arg>
                    <arg>${project.build.directory}/native/include</arg>
                </compilerArgs>
            </configuration>
        </plugin>

[hendriks73]

But... to use the plugin on Java9/10, a dependency definitely needs to be updated. Please see #18.

[ctubbsii]

The 1.0-alpha-9 version was released. That milestone should be closed and this issue bumped to the next milestone (unless it was already fixed).

[dantran]

@hendriks73 is this fixed in alpha-9?

[hendriks73]

No, it's not.

Java9 and 10 do not have a javah executable anymore. So the native plugin should either

• somehow execute javac with the appropriate flags (not sure, if that's possible)
• show a warning that javah is not supported anymore
• find some other programmatic way to generate headers

That aside, users can use the regular compiler plugin to produce header files, as shown above.

There is one project - https://github.com/Glavo/gjavah it looks like an implementation of javah in pure java. It is mit licensed. Maybe it can be used instead of javah?

[ctubbsii]

Given that javac -h works even better than javah, I don't really see why this even needs to be maintained anymore. It's easy enough to update the maven-compiler-plugin to use -h and, if necessary, it's not too difficult to use profiles to support different Java versions to support pre- and post-Java8, which added the -h flag to javac.

[svby]

This is true but javac -h becomes useless when working with other JVM languages as it only operates on .java source files 😕

[ryantheseer]

Given that javac -h works even better than javah, I don't really see why this even needs to be maintained anymore. It's easy enough to update the maven-compiler-plugin to use -h and, if necessary, it's not too difficult to use profiles to support different Java versions to support pre- and post-Java8, which added the -h flag to javac.

I see that we can change org.codehaus.mojo.natives.javah.JavahExecutable to use javac -h instead of javah, but I believe the command-line changed from referring to the class file with its package name to using the .java file. Let's say I successfully branch this project, make that small change, build and install the plugin for maven, how would I call the plugin differently?

[ryantheseer]

Also, if I understand correctly, this plugin allows you to define a build artifact that builds the JNI header and the native library (.so, .dll, .dylib) in the same build call. Do I have to separate those into two steps if I use the maven-compiler-plugin as noted above?

[ryantheseer]

What I've done for now is to hack the org.codehaus.mojo.natives.javah.JavahExecutable to use javac -h instead of javah, and modified my pom.xml to use the .java source path for the <javahClassName> property instead of using the dot-separated package and class name. I can build it with JDK8 that way. Next step is to try with a newer JDK.