Script to get latest revision from svn as a git repository

Here is a script that I use to fetch the latest revision of a svn project. The trick lies in finding that revision number. It isn't the Revision of the repository but the Last Changed Rev. The rest is straightforward git svn.

#!/bin/sh

SVN_URL=$1
GIT_DIR=$2
REV=`svn info $SVN_URL | awk -F': ' '/Last Changed Rev/ { print $2 }'`

mkdir -p $GIT_DIR
cd $GIT_DIR
git svn init --stdlayout $SVN_URL
git svn fetch -r $REV:HEAD

eclipse on vista 64

Last week I removed the JRE that came with my laptop not realizing that eclipse needs a 32 bit JVM. It never tells you this, it just fails to start up. I finally found a .log (yes, without a prefix) in the .metadata directory of the workspace that I was trying to start. It had this exception

java.lang.UnsatisfiedLinkError: Cannot load 32-bit SWT libraries on 64-bit JVM

.

Now I knew what happened and off-course now I have twice the amount of JDK's to manage on my system.

JASIG Conference

This week I'm visiting Dallas (TX) to attend the JASIG Spring 2009 Conference. The BA flight in was long and the conference hotel is nice.

Not out of memory

When I tried to build Sakai on a Solaris box today it failed. The only cryptic clue I received was this stacktrace

[exec] java.io.IOException: Cannot run program "env": error=12, Not enough space env=""
[exec] at java.lang.ProcessBuilder.start(ProcessBuilder.java:459)
[exec] at java.lang.Runtime.exec(Runtime.java:593)
[exec] at java.lang.Runtime.exec(Runtime.java:431)
[exec] at java.lang.Runtime.exec(Runtime.java:328)
[exec] at hidden.org.codehaus.plexus.util.cli.CommandLineUtils.getSystemEnvVars(CommandLineUtils.java:218)
[exec] at hidden.org.codehaus.plexus.util.cli.CommandLineUtils.getSystemEnvVars(CommandLineUtils.java:182)
[exec] at org.apache.maven.project.interpolation.RegexBasedModelInterpolator.<init>(RegexBasedModelInterpolator.java:63)
[exec] at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
[exec] at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
[exec] at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
[exec] at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
[exec] at java.lang.Class.newInstance0(Class.java:355)
[exec] at java.lang.Class.newInstance(Class.java:308)
[exec] at org.codehaus.plexus.component.factory.java.JavaComponentFactory.newInstance(JavaComponentFactory.java:44)
[exec] at org.codehaus.plexus.DefaultPlexusContainer.createComponentInstance(DefaultPlexusContainer.java:1464)
[exec] at org.codehaus.plexus.component.manager.AbstractComponentManager.createComponentInstance(AbstractComponentManager.java:93)
[exec] at org.codehaus.plexus.component.manager.ClassicSingletonComponentManager.getComponent(ClassicSingletonComponentManager.java:92)
[exec] at org.codehaus.plexus.DefaultPlexusContainer.lookup(DefaultPlexusContainer.java:331)
[exec] at org.codehaus.plexus.component.composition.FieldComponentComposer.assignRequirementToField(FieldComponentComposer.java:129)
[exec] at org.codehaus.plexus.component.composition.FieldComponentComposer.assembleComponent(FieldComponentComposer.java:73)
[exec] at org.codehaus.plexus.component.composition.DefaultComponentComposerManager.assembleComponent(DefaultComponentComposerManager.java:68)
[exec] at org.codehaus.plexus.DefaultPlexusContainer.composeComponent(DefaultPlexusContainer.java:1486)
[exec] at org.codehaus.plexus.personality.plexus.lifecycle.phase.CompositionPhase.execute(CompositionPhase.java:29)
[exec] at org.codehaus.plexus.lifecycle.AbstractLifecycleHandler.start(AbstractLifecycleHandler.java:101)
[exec] at org.codehaus.plexus.component.manager.AbstractComponentManager.startComponentLifecycle(AbstractComponentManager.java:105)
[exec] at org.codehaus.plexus.component.manager.AbstractComponentManager.createComponentInstance(AbstractComponentManager.java:95)
[exec] at org.codehaus.plexus.component.manager.ClassicSingletonComponentManager.getComponent(ClassicSingletonComponentManager.java:92)
[exec] at org.codehaus.plexus.DefaultPlexusContainer.lookup(DefaultPlexusContainer.java:331)
[exec] at org.codehaus.plexus.component.composition.FieldComponentComposer.assignRequirementToField(FieldComponentComposer.java:129)
[exec] at org.codehaus.plexus.component.composition.FieldComponentComposer.assembleComponent(FieldComponentComposer.java:73)
[exec] at org.codehaus.plexus.component.composition.DefaultComponentComposerManager.assembleComponent(DefaultComponentComposerManager.java:68)
[exec] at org.codehaus.plexus.DefaultPlexusContainer.composeComponent(DefaultPlexusContainer.java:1486)
[exec] at org.codehaus.plexus.personality.plexus.lifecycle.phase.CompositionPhase.execute(CompositionPhase.java:29)
[exec] at org.codehaus.plexus.lifecycle.AbstractLifecycleHandler.start(AbstractLifecycleHandler.java:101)
[exec] at org.codehaus.plexus.component.manager.AbstractComponentManager.startComponentLifecycle(AbstractComponentManager.java:105)
[exec] at org.codehaus.plexus.component.manager.AbstractComponentManager.createComponentInstance(AbstractComponentManager.java:95)
[exec] at org.codehaus.plexus.component.manager.ClassicSingletonComponentManager.getComponent(ClassicSingletonComponentManager.java:92)
[exec] at org.codehaus.plexus.DefaultPlexusContainer.lookup(DefaultPlexusContainer.java:331)
[exec] at org.codehaus.plexus.embed.Embedder.lookup(Embedder.java:78)
[exec] at org.apache.maven.cli.MavenCli.createMavenInstance(MavenCli.java:474)
[exec] at org.apache.maven.cli.MavenCli.main(MavenCli.java:257)
[exec] at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
[exec] at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
[exec] at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
[exec] at java.lang.reflect.Method.invoke(Method.java:597)
[exec] at org.codehaus.classworlds.Launcher.launchEnhanced(Launcher.java:315)
[exec] at org.codehaus.classworlds.Launcher.launch(Launcher.java:255)
[exec] at org.codehaus.classworlds.Launcher.mainWithExitCode(Launcher.java:430)
[exec] at org.codehaus.classworlds.Launcher.main(Launcher.java:375)
[exec] Caused by: java.io.IOException: error=12, Not enough space
[exec] at java.lang.UNIXProcess.forkAndExec(Native Method)
[exec] at java.lang.UNIXProcess.<init>(UNIXProcess.java:53)
[exec] at java.lang.ProcessImpl.start(ProcessImpl.java:65)
[exec] at java.lang.ProcessBuilder.start(ProcessBuilder.java:452)
[exec] ... 48 more

After digging around it and trying different ulimit settings it turned out to be that the /tmp partition was too full.

Every Class

This week I wanted to find out which classes are loaded in running environment.

One way of achieving this is replacing the boot classloader and finding a way to keep a reference to every loaded class by every child classloader. This sounded like too much work and I find it very scary to replace system classes with my own which probably don't have the same quality.

Another approach is to write a javaagent. This gives access to the java.lang.instrument.Instrumentation class which in turn has the getAllLoadedClasses() method. Exactly the information I was after and without many nasty side effects or jumping through burning hoops.

Now that I found this information I needed a way to publish it. A colleague of mine pointed me in the direction of JMX. Using JConsole to view which classes are loaded sound great to me so after a little hacking I came up with a javaagent which registers itself as an MBean.

Here's the code:

MANIFEST.MF

Manifest-Version: 1.0
Premain-Class: somecoder.classes.Classes

ClassesMBean.java

package somecoder.classes;

public interface ClassesMBean {
 String[] getClasses();
 long getClassCount();
}

Classes.java

package somecoder.classes;

import java.lang.instrument.Instrumentation;
import java.lang.management.ManagementFactory;

import javax.management.ObjectName;

public final class Classes implements ClassesMBean {
 private Instrumentation inst;

 private Classes(final Instrumentation inst) {
  this.inst = inst;
 }

 public static void premain(final String agentArgs,
   final Instrumentation inst) {
  try {
   final Classes classLister = new Classes(inst);
    ManagementFactory.getPlatformMBeanServer().registerMBean(classLister, new ObjectName("Classes:type=Agent"));
  } catch (Exception e) {
   e.printStackTrace();
  }
 }

 public long getClassCount() {
  return inst.getAllLoadedClasses().length;
 }

 public String[] getClasses() {
  final Class[] classes = inst.getAllLoadedClasses();
  final String[] strings = new String[classes.length];
  for (int i = 0; i < classes.length; i++) {
   strings[i] = classes[i].getName();
  }
  return strings;
 }
}