In my last post BuildListener using Groovy In Ant Scriptdef, I got a scripted BuildListener to work. Was wondering if there were a way to use a Proxy to stand in for the listener.
See update below for another attempt that succeeds.
In short, I can’t. The first problem was classloader issues, but I think I fixed that by clearing the CLASSPATH:
set CLASSPATH =
Then a host of issues, until finally I give up. I think the big complexity is that BuildListener is an Interface. That means you have to jump hoops to proxy it. I’m sure Groovy can do this, but I don’t see it yet. May need more info on Groovy’s MOP.
Perhaps there is too much indirection being used. Is modern software engineering just ingenious ways to hide a GOTO? Just kidding.
Using commons-proxy library
Apache’s commons-proxy puts a more usable framework around different proxy factories.
Listing 1 – Proxy using Javassist library
import org.apache.commons.proxy.factory.javassist.*
import java.lang.reflect.*
import org.apache.commons.proxy.*
import org.apache.tools.ant.*
class MyListener implements Invoker {
static int count = 0;
Object invoke(Object proxy, Method method, Object[] arguments)
throws Throwable{
new File("finished.run").setText("count: ${count++}")
}
}
MyListener proxy = new MyListener()
java.lang.ClassLoader loader = proxy.class.getClassLoader()
JavassistProxyFactory factory = new JavassistProxyFactory()
Object listener = factory.createInvokerProxy(
loader,
proxy,
[BuildListener.class] as Class[]
);
project.addBuildListener(listener)
// end source
Listing 2 – build script
<project name="listener" default="default" basedir=".">
<!--
File: build.xml, author: J.Betancourt,
date:2011-08-18T2137
-->
<path id="libs">
<fileset dir="lib">
<include name="commons-proxy-1.0.jar" />
<include name="javassist.jar"/>
<include name="groovy-all-1.8.0.jar"/>
</fileset>
</path>
<!-- Groovy library -->
<typedef resource="org/codehaus/groovy/antlib.xml" classpathref="libs" />
<!-- sets a BuildListener to the project -->
<scriptdef name="set-listener" language="Groovy"
classpathref="libs" src="lib/BuildListener.groovy">
<attribute name="endTarget"/>
</scriptdef>
<!-- install the listener -->
<set-listener endTarget="list"/>
<target name="default">
<fail message="doh!"/>
</target>
</project>
Listing 3 – stacktrace snippet
C:tempantgroovyListener>ant
Buildfile: C:tempantgroovyListenerbuild.xml
BUILD FAILED
java.lang.ClassCircularityError: groovy/runtime/metaclass/java/io/FileMetaClass
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:169)
at groovy.lang.MetaClassRegistry$MetaClassCreationHandle.createWithCustomLookup(MetaClassRegistry.java:127)
at groovy.lang.MetaClassRegistry$MetaClassCreationHandle.create(MetaClassRegistry.java:122)
at org.codehaus.groovy.reflection.ClassInfo.getMetaClassUnderLock(ClassInfo.java:165)
at org.codehaus.groovy.reflection.ClassInfo.getMetaClass(ClassInfo.java:182)
at org.codehaus.groovy.runtime.metaclass.MetaClassRegistryImpl.getMetaClass(MetaClassRegistryImpl.java:242)
at org.codehaus.groovy.runtime.InvokerHelper.getMetaClass(InvokerHelper.java:751)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.createCallConstructorSite(CallSiteArray.java:71)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCallConstructor(CallSiteArray.java:54)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callConstructor(AbstractCallSite.java:182)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callConstructor(AbstractCallSite.java:190)
at MyListener.invoke(Script1.groovy:10)
at JavassistUtilsGenerated_0.messageLogged(JavassistUtilsGenerated_0.java)
at org.apache.tools.ant.Project.fireMessageLoggedEvent(Project.java:2254)
at org.apache.tools.ant.Project.fireMessageLogged(Project.java:2290)
This works, but just as wordy as the original using a BuildListener class implementation.
import org.apache.tools.ant.*
listenerMap = [
theTarget : attributes.get("endtarget"),
buildFinished: { event ->
new File("finished.run").
setText(
"Build Finished: message='${event.message}' exception='${event.exception}'"
)
project.executeTarget(listenerMap.theTarget)
},
buildStarted : {},
messageLogged : {},
targetFinished : {},
targetStarted : {},
taskFinished : {},
taskStarted : {},
]
listener = listenerMap as BuildListener
project.addBuildListener(listener )
Uses the technique outlined at:
Groovy Way to implement interfaces
Conclusion
Updates
Further Reading
- commons-proxy
- Overriding Java methods in Groovy for unit testing
- http://stackoverflow.com/questions/4244038/groovy-ant-task-using-different-classloader
- http://jira.codehaus.org/browse/GROOVY-3064
- http://stackoverflow.com/questions/472559/how-to-load-an-optional-task-into-ant-without-lib-or-global-installation
- http://stackoverflow.com/questions/3862525/how-to-create-a-proxy-of-an-interface-in-java
- How to create proxy for List interface ?
- Groovy Ant Task using different classloader
ant task setContextClassloader- AntBuilder: Groovy Meets Ant
- Practically Groovy: The @Delegate annotation
- Extending Ant
- Groovy
- Using Ant from Groovy
- Scriptdef
- PropertyFile Task
- Ant Groovy Task
- Ouroboros
- SED
Listing 4 – Full stacktrace
C:tempantgroovyListener>ant
Buildfile: C:tempantgroovyListenerbuild.xml
BUILD FAILED
java.lang.ClassCircularityError: groovy/runtime/metaclass/java/io/FileMetaClass
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:169)
at groovy.lang.MetaClassRegistry$MetaClassCreationHandle.createWithCustomLookup(MetaClassRegistry.java:127)
at groovy.lang.MetaClassRegistry$MetaClassCreationHandle.create(MetaClassRegistry.java:122)
at org.codehaus.groovy.reflection.ClassInfo.getMetaClassUnderLock(ClassInfo.java:165)
at org.codehaus.groovy.reflection.ClassInfo.getMetaClass(ClassInfo.java:182)
at org.codehaus.groovy.runtime.metaclass.MetaClassRegistryImpl.getMetaClass(MetaClassRegistryImpl.java:242)
at org.codehaus.groovy.runtime.InvokerHelper.getMetaClass(InvokerHelper.java:751)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.createCallConstructorSite(CallSiteArray.java:71)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCallConstructor(CallSiteArray.java:54)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callConstructor(AbstractCallSite.java:182)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callConstructor(AbstractCallSite.java:190)
at MyListener.invoke(Script1.groovy:10)
at JavassistUtilsGenerated_0.messageLogged(JavassistUtilsGenerated_0.java)
at org.apache.tools.ant.Project.fireMessageLoggedEvent(Project.java:2254)
at org.apache.tools.ant.Project.fireMessageLogged(Project.java:2290)
at org.apache.tools.ant.Project.log(Project.java:470)
at org.apache.tools.ant.Project.log(Project.java:459)
at org.apache.tools.ant.AntClassLoader.log(AntClassLoader.java:396)
at org.apache.tools.ant.AntClassLoader.findClass(AntClassLoader.java:1310)
at org.apache.tools.ant.AntClassLoader.loadClass(AntClassLoader.java:1064)
at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:169)
at groovy.lang.MetaClassRegistry$MetaClassCreationHandle.createWithCustomLookup(MetaClassRegistry.java:127)
at groovy.lang.MetaClassRegistry$MetaClassCreationHandle.create(MetaClassRegistry.java:122)
at org.codehaus.groovy.reflection.ClassInfo.getMetaClassUnderLock(ClassInfo.java:165)
at org.codehaus.groovy.reflection.ClassInfo.getMetaClass(ClassInfo.java:182)
at org.codehaus.groovy.runtime.metaclass.MetaClassRegistryImpl.getMetaClass(MetaClassRegistryImpl.java:242)
at org.codehaus.groovy.runtime.InvokerHelper.getMetaClass(InvokerHelper.java:751)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.createCallConstructorSite(CallSiteArray.java:71)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCallConstructor(CallSiteArray.java:54)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callConstructor(AbstractCallSite.java:182)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callConstructor(AbstractCallSite.java:190)
at MyListener.invoke(Script1.groovy:10)
at JavassistUtilsGenerated_0.taskFinished(JavassistUtilsGenerated_0.java)
at org.apache.tools.ant.Project.fireTaskFinished(Project.java:2206)
at org.apache.tools.ant.Task.perform(Task.java:364)
at org.apache.tools.ant.Target.execute(Target.java:390)
at org.apache.tools.ant.helper.ProjectHelper2.parse(ProjectHelper2.java:180)
at org.apache.tools.ant.ProjectHelper.configureProject(ProjectHelper.java:82)
at org.apache.tools.ant.Main.runBuild(Main.java:793)
at org.apache.tools.ant.Main.startAnt(Main.java:217)
at org.apache.tools.ant.launch.Launcher.run(Launcher.java:280)
at org.apache.tools.ant.launch.Launcher.main(Launcher.java:109)
Total time: 1 second
java.lang.ClassCircularityError: groovy/runtime/metaclass/java/io/FileMetaClass
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:169)
at groovy.lang.MetaClassRegistry$MetaClassCreationHandle.createWithCustomLookup(MetaClassRegistry.java:127)
at groovy.lang.MetaClassRegistry$MetaClassCreationHandle.create(MetaClassRegistry.java:122)
at org.codehaus.groovy.reflection.ClassInfo.getMetaClassUnderLock(ClassInfo.java:165)
at org.codehaus.groovy.reflection.ClassInfo.getMetaClass(ClassInfo.java:182)
at org.codehaus.groovy.runtime.metaclass.MetaClassRegistryImpl.getMetaClass(MetaClassRegistryImpl.java:242)
at org.codehaus.groovy.runtime.InvokerHelper.getMetaClass(InvokerHelper.java:751)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.createCallConstructorSite(CallSiteArray.java:71)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCallConstructor(CallSiteArray.java:54)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callConstructor(AbstractCallSite.java:182)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callConstructor(AbstractCallSite.java:190)
at MyListener.invoke(Script1.groovy:10)
at JavassistUtilsGenerated_0.messageLogged(JavassistUtilsGenerated_0.java)
at org.apache.tools.ant.Project.fireMessageLoggedEvent(Project.java:2254)
at org.apache.tools.ant.Project.fireMessageLogged(Project.java:2290)
at org.apache.tools.ant.Project.log(Project.java:470)
at org.apache.tools.ant.Project.log(Project.java:459)
at org.apache.tools.ant.AntClassLoader.log(AntClassLoader.java:396)
at org.apache.tools.ant.AntClassLoader.findClass(AntClassLoader.java:1310)
at org.apache.tools.ant.AntClassLoader.loadClass(AntClassLoader.java:1064)
at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:169)
at groovy.lang.MetaClassRegistry$MetaClassCreationHandle.createWithCustomLookup(MetaClassRegistry.java:127)
at groovy.lang.MetaClassRegistry$MetaClassCreationHandle.create(MetaClassRegistry.java:122)
at org.codehaus.groovy.reflection.ClassInfo.getMetaClassUnderLock(ClassInfo.java:165)
at org.codehaus.groovy.reflection.ClassInfo.getMetaClass(ClassInfo.java:182)
at org.codehaus.groovy.runtime.metaclass.MetaClassRegistryImpl.getMetaClass(MetaClassRegistryImpl.java:242)
at org.codehaus.groovy.runtime.InvokerHelper.getMetaClass(InvokerHelper.java:751)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.createCallConstructorSite(CallSiteArray.java:71)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCallConstructor(CallSiteArray.java:54)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callConstructor(AbstractCallSite.java:182)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callConstructor(AbstractCallSite.java:190)
at MyListener.invoke(Script1.groovy:10)
at JavassistUtilsGenerated_0.taskFinished(JavassistUtilsGenerated_0.java)
at org.apache.tools.ant.Project.fireTaskFinished(Project.java:2206)
at org.apache.tools.ant.Task.perform(Task.java:364)
at org.apache.tools.ant.Target.execute(Target.java:390)
at org.apache.tools.ant.helper.ProjectHelper2.parse(ProjectHelper2.java:180)
at org.apache.tools.ant.ProjectHelper.configureProject(ProjectHelper.java:82)
at org.apache.tools.ant.Main.runBuild(Main.java:793)
at org.apache.tools.ant.Main.startAnt(Main.java:217)
at org.apache.tools.ant.launch.Launcher.run(Launcher.java:280)
at org.apache.tools.ant.launch.Launcher.main(Launcher.java:109)
groovy/runtime/metaclass/java/io/FileMetaClass
“Timeless” solo 12 string guitar played by Ralph Towner on his “Solo Concert” CD. YouTube