Where does System.err of Maven plugin go?

[basinilya]

Hi List.
I'm trying to debug the error (not reproducible with command line maven):

    JAXB errors arose while SchemaGen compiled sources to XML. (org.codehaus.mojo:jaxb2-maven-plugin:2.3.1:schemagen:schemagen:generate-resources)

    org.apache.maven.plugin.MojoExecutionException: JAXB errors arose while SchemaGen compiled sources to XML.
    	at org.codehaus.mojo.jaxb2.schemageneration.AbstractXsdGeneratorMojo.performExecution(AbstractXsdGeneratorMojo.java:385)

According to
https://github.com/mojohaus/jaxb2-maven-plugin/blob/a52f6c270f28753b4d92b71e36e629ad2c3a7ad8/src/main/java/org/codehaus/mojo/jaxb2/schemageneration/AbstractXsdGeneratorMojo.java#L411
it calls com.sun.tools.jxc.SchemaGenerator.run()

and according to the decompilation of SchemaGenerator$Runner it should print the errors to System.err before returning false:

/* 243 */       boolean res = task.call().booleanValue();
/*     */       
/* 245 */       for (Diagnostic<? extends JavaFileObject> d : diagnostics.getDiagnostics()) {
/* 246 */         System.err.println(d.toString());
/*     */       }
/* 248 */       return res;

I tried to run eclipsec.exe and I also checked the .log file in the Eclipse Workspace, but nothing is printed there. I also attached a debugger ti Eclipse, but the main Eclipse process doesn't load the above classes. Looks like m2e forks.

On the mailing list I was advised to install the M2E-Feature 'org.eclipse.m2e.logback.feature' which adds the Maven-Console that should show the print-out of Maven Plug-ins executed during the M2E-build within Eclipse.

I already had this feature installed, but the Maven Console did not show anything relevant.

Please tell me at least how to put a working breakpoint in SchemaGenerator$Runner. Is this really a forked process? How to start it in debug mode?

[mickaelistria]

Did you define some lifecycle mapping metadata for the execution of this mojo? Mojo execution is usually not a subprocess.
To debug the Eclipse IDE, you need to install "Ecipse Plugin Development Environment" from the main site in Help > Install New Software. Then you can start a "child" Eclipse IDE which will be connected to Eclipse debugger, so you can try adding breakpoints to AbstractXsdGeneratorMojo .
HTH

[basinilya]

@mickaelistria I'll try. Meanwhile do you know how to properly add maven plugin jars to debug classpath of a pde project? Should I manually add them to the classpath of the project named, say, "org.eclipse.m2e.maven.runtime"?

[mickaelistria]

I'm not sure what you're trying to achieve. The configuration of project is described in https://github.com/eclipse-m2e/m2e-core/blob/master/CONTRIBUTING.md#-developer-resources . I don't think you should try to modify classpath here as it's rules by OSGi/MANIFEST.MF, and we won't add into m2e support for random Maven plugins in the code org.eclipse.m2e.maven.runtime bundle. Only official or mainstream Maven plugins can be supported in core parts, other plugins will require to create a dedicated Eclipse plugin to support them.

[basinilya]

I mean org.codehaus.mojo.jaxb2-maven-plugin is not a dependency of any m2e plugins, but I need it in debug classpath to put a breakpoint in AbstractXsdGeneratorMojo when I choose Run -> Eclipse application

[mickaelistria]

I suggest you just import the code of jaxb2-maven-plugin in your workspace then. Make sure you pick the right tag!

[basinilya]

The problem is now solved.

• I didn't manage to reproduce it using Run As -> Eclipse application : doing so was adding some extra libraries to the eclipse classpath completely breaking JXC.
• Instead I added to eclipse.ini, -vmargs: -Xrunjdwp:transport=dt_socket,address=0.0.0.0:7878,server=y,suspend=y
  and debugged the plugin project org.eclipse.m2e.maven.runtime as a remote java application
• I had to make sure that in the PDE workspace there're no installed JREs below the "justj" bundled with Eclipse for the JDK sources to be attached correctly
• For some reason the entry/exit breakpoints weren't hitting on SchemaGenerator$Runner.compile(), but they were on the task it was calling: com.sun.tools.javac.api.JavacTaskImpl.call(). When the exit breakpoint hit I navigated to the parent frame and inpsected the local variable diagnostics and got the error messages I was looking for.

The reason why nothing was printed to System.err is that System.err is not used at all in the SchemaGenerator implemenation from org.glassfish.jaxb:jaxb-jxc:2.2.11. The local variable diagnostics is never read and its contents are lost.

So the solution is to upgrade to a more recent version of jaxb2-maven-plugin or jaxb-ri

The errors I was looking for were:

import com.common.util.xml.HasLateValidate;
                          ^, C:\ftpjob\CommonJavaProject\src\com\common\ftpconfiguration\Subtask.java:13: error: package com.common.util.xml does not exist
import com.common.util.xml.JAXB2ValidationEventCollector;
                          ^, C:\ftpjob\CommonJavaProject\src\com\common\ftpconfiguration\FtpConfig.java:23: error: package com.common.util.xml does not exist
...