help needed on gwt-maven-plugin

[nicolas.deloof]

Hi,

the gwt-maven-plugin development has a Classloader issue with tomcat
embedded
http://jira.codehaus.org/browse/MGWT-14

We have no idea of what's wrong, so any of you with ClassLoader /
Tomcat embedded skills would be welcome to help if possible.
Please apologies for "spaming" this group for a maven-dev related
issue.


The plugin generates a command script to lanch the GWT Shell from
command line. To bypass windows command line length limitation, it
uses a "booter" to setup an URLClassLoader with all project/gwt
libraries and run the GWTShell.main().

But the shell fails with :

[WARN] StandardContext[]Error loading WebappClassLoader
delegate: false
repositories:
----------> Parent Classloader:
sun.misc.Launcher$AppClassLoader@1ba34f2
com.google.gwt.dev.shell.GWTShellServlet
java.lang.ClassNotFoundException:
com.google.gwt.dev.shell.GWTShellServlet
org.apache.catalina.loader.WebappClassLoader.loadClass
(WebappClassLoader.java:1340)


To reproduce this issue, checkout https://svn.codehaus.org/mojo/trunk/mojo/gwt-maven-plugin
run "mvn clean install"
goto target\it\gwt-compile
run "mvn gwt:gwt"

Cheers,
Nicolas

[Scott Blum]

Hi Nicolas,

Can you supply the actual script produced and any Java classes that are used to setup the "booter"?

Thanks,

Scott

[nicolas de loof]

You can get the test project from http://people.apache.org/~nicolas/MGWT-14/ as a ZIP of browse its content.

plugin source is code at https://svn.codehaus.org/mojo/trunk/mojo/gwt-maven-plugin

The maven plugin creates :

-  a classpath entries list in target/gwt.classpath file (warning : files path are absolute)

-  a run.cmd script to lanch de GWT Shell using a booter

The "ForkBooter" class is used to launch a JVM and build a classloader with all required classpath entries, without requirement for a long command line :

/**

 * A (simplified) surefire-like bootstrapper to run some GWT component in a forked JVM without limitation of command

 * line length to define the classpath.

 * 

 * @author ndeloof

 * @version $Id: ForkBooter.java 8738 2009-01-17 21:15:43Z olamy $

 */

public class ForkBooter

{

    public static void main( String[] args )

        throws Exception

    {

        String fileName = args[0];

        String className = args[1];

        ClassLoader cl = getClassLoader( fileName );

        Class<?> gwt = cl.loadClass( className );

        

        Thread.currentThread().setContextClassLoader( cl );

        

        Method method = gwt.getMethod( "main", new Class[] { String[].class } );

        String[] compilerArgs = new String[args.length - 1];

        System.arraycopy( args, 1, compilerArgs, 0, args.length - 1 );

        method.invoke( null, (Object) compilerArgs );

    }

    private static ClassLoader getClassLoader( String fileName )

        throws FileNotFoundException, IOException, MalformedURLException

    {

        BufferedReader reader = new BufferedReader( new FileReader( fileName ) );

        List<URL> classpath = new LinkedList<URL>();

        String line;

        while ( ( line = reader.readLine() ) != null )

        {

            classpath.add( new File( line ).toURI().toURL() );

        }

        URL[] urls = (URL[]) classpath.toArray( new URL[classpath.size()] );

        return new URLClassLoader( urls, ClassLoader.getSystemClassLoader() );

    }

}

2009/1/20 Scott Blum <sco...@google.com>

[Scott Blum]

Thanks, nicolas.  Your test reproduced an issue, but I was unable to get Tomcat to work properly.  We will probably not fix this for 1.6 since Jetty works fine.

http://code.google.com/p/google-web-toolkit/issues/detail?id=1032

Scott

[John Tamplin]

On Tue, Jan 20, 2009 at 9:41 PM, Scott Blum <sco...@google.com> wrote:

Thanks, nicolas.  Your test reproduced an issue, but I was unable to get Tomcat to work properly.  We will probably not fix this for 1.6 since Jetty works fine.

http://code.google.com/p/google-web-toolkit/issues/detail?id=1032

Actually, I think jetty has a similar issue (see the internal error report Lex is looking at) -- I think the root cause is jarjar missed some reflective references to classes, so code is looking for classes under the un-mangled name yet the classes have been renamed inside our jar.

Can you try it with surpressing the jarjar mangling?

--
John A. Tamplin
Software Engineer (GWT), Google

[Scott Blum]

Jarjar is a trunk issue that I believe is unrelated.

[nicolas de loof]

The same script can run the shell with a "inlined" classpath :

set CLASSPATH=D:\platina\repository\com\google\gwt\gwt-user\1.5.3\gwt-user-1.5.3.jar;D:\platina\repository\com\google\gwt\gwt-dev\1.5.3\gwt-dev-1.5.3-windows.jar

...

java  -cp %CLASSPATH% -Dcatalina.base="D:\projets\apache\gwt-maven-plugin\target\it\gwt-compile\target\tomcat"   com.google.gwt.dev.GWTShell -gen ...

But this option fails on windows whith command line limitation on large projects with lot's of dependencies.

So I don't thing this issue is related to some jarjar packaging. It seems the TomcatEmbedded doesn't support to run inside a hierarchized classloader (looks really strange) and is fine only when all dependencies are set in the Classpath.

2009/1/21 Scott Blum <sco...@google.com>

[Olivier Modica]

Hi,

I wrote a blog post about this exact subject here:
http://development.lombardi.com/?p=380

I believe this will help. My understanding is that
EmbeddedTomcatServer doesn't set up the ClassLoader as you would
expect.

Thanks,
Olivier.