Running GWT Devmode with Xvfb on CentOS

Question

I'm trying to run GWT Devmode with Ant on CentOS using Xvfb and I'm getting what appears to be a Java version error. The beginning of the stacktrace is

[java] JVM args ignored when same JVM is used
[java] Working directory ignored when same JVM is used.
[java] java.lang.NoClassDefFoundError: java.util.concurrent.Semaphore
[java]    at org.apache.tools.ant.taskdefs.ExecuteJava.execute(ant-1.6.5.jar.so)
[java]    at org.apache.tools.ant.taskdefs.Java.run(ant-1.6.5.jar.so)
[java]    at org.apache.tools.ant.taskdefs.Java.executeJava(ant-1.6.5.jar.so)
[java]    at org.apache.tools.ant.taskdefs.Java.execute(ant-1.6.5.jar.so)
[java]    at org.apache.tools.ant.UnknownElement.execute(ant-1.6.5.jar.so)
[java]    at org.apache.tools.ant.Task.perform(ant-1.6.5.jar.so)
[java]    at org.apache.tools.ant.Target.execute(ant-1.6.5.jar.so)
[java]    at org.apache.tools.ant.Target.performTasks(ant-1.6.5.jar.so)
[java]    at org.apache.tools.ant.Project.executeSortedTargets(ant-1.6.5.jar.so)
[java]    at org.apache.tools.ant.Project.executeTarget(ant-1.6.5.jar.so)
[java]    at org.apache.tools.ant.helper.DefaultExecutor.executeTargets(ant-1.6.5.jar.so)
[java]    at org.apache.tools.ant.Project.executeTargets(ant-1.6.5.jar.so)
[java]    at org.apache.tools.ant.Main.runBuild(ant-1.6.5.jar.so)
[java]    at org.apache.tools.ant.Main.startAnt(ant-1.6.5.jar.so)
[java]    at org.apache.tools.ant.launch.Launcher.run(ant-launcher-1.6.5.jar.so)
[java]    at org.apache.tools.ant.launch.Launcher.main(ant-launcher-1.6.5.jar.so)
[java] Caused by: java.lang.NoClassDefFoundError: java.util.concurrent.Semaphore
[java]    at com.google.gwt.dev.DevModeBase.<init>(DevModeBase.java:749)
[java]    at com.google.gwt.dev.DevMode.<init>(DevMode.java:341)
[java]    at com.google.gwt.dev.DevMode.main(DevMode.java:309)
[java]    at java.lang.reflect.Method.invoke(libgcj.so.7rh)

I installed Sun's java 1.7.0 and I think it's set properly. It shows up when I do "java -version" and when I do "alternatives --config java" (version 1.4.2 is set as the default but I've changed the current version).

This is the ant task I'm running. Note that I've tried all combinations of fork="true|false" and spawn="true|false"

<target name="devmode" depends="" description="Run development mode">
    <java fork="true" classname="com.google.gwt.dev.DevMode" 
        dir="${basedir}/war" spawn="true">
        <classpath>
            <pathelement location="src" />
            <path refid="project.class.path" />
            <path refid="tools.class.path" />
        </classpath>
        <jvmarg value="-Xmx512M" />
        <jvmarg value="-javaagent:${appengine.folder}/lib/agent/appengine-agent.jar" />
        <jvmarg value="-Duser.dir=${basedir}/war" />
        <arg line="-war" />
        <arg value="${basedir}/war" />
        <arg line="-logLevel" />
        <arg value="INFO" />
        <arg value="-server" />
        <arg value="com.google.appengine.tools.development.gwt.AppEngineLauncher" />
        <arg value="net.bookedin.bam.BAM" />

    </java>

</target>

My $CLASSPATH variable (assuming that matters) shows: /usr/java/jdk1.7.0_02/lib

score 0 · Accepted Answer · answered Feb 14 '12 at 12:23

Discovered the problem. While I had updated java to 1.7.0, javac was still pointing to the old 1.4.2 version. I used alternatives to install the new version and switch to it:

alternatives --install /usr/bin/javac javac /usr/java/jdk1.7.0_02/bin/javac 1
alternatives --config javac

Running GWT Devmode with Xvfb on CentOS

1 Answers1