Hello,
I looked through AspectJ's Load Time Weaver and I combined it with your code
suggestion.
This is what I got out
import java.lang.instrument.ClassFileTransformer;
import java.lang.instrument.IllegalClassFormatException;
import java.security.ProtectionDomain;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import org.aspectj.weaver.loadtime.Aj;
import org.aspectj.weaver.loadtime.DefaultWeavingContext;
import org.aspectj.weaver.loadtime.definition.Definition;
import org.aspectj.weaver.tools.WeavingAdaptor;
public class AspectJLTW implements ClassFileTransformer {
private class MonitorWeavingContext extends DefaultWeavingContext {
public MonitorWeavingContext(ClassLoader loader) {
super(loader);
}
@Override
public List getDefinitions(ClassLoader loader, WeavingAdaptor adaptor) {
List definitions = new ArrayList();
Definition d = new Definition();
d.getAspectClassNames().add(aspectName);
d.appendWeaverOptions("-Xjoinpoints:synchronization");
definitions.add(d);
return definitions;
}
}
private final Map<ClassLoader, Aj> mapFromClassLoaderToAj;
private final String aspectName;
public AspectJLTW(String aspectName) {
try {
mapFromClassLoaderToAj = new ConcurrentHashMap<ClassLoader, Aj>();
this.aspectName = aspectName;
} catch (Exception e) {
throw new ExceptionInInitializerError(
"could not initialize JSR163 preprocessor due to: "
+ e.toString());
}
}
/**
* Weaving delegation
*
* @param loader
* the defining class loader
* @param className
* the name of class beeing loaded
* @param classBeingRedefined
* when hotswap is called
* @param protectionDomain
* @param bytes
* the bytecode before weaving
* @return the weaved bytecode
*/
public byte[] transform(ClassLoader loader, String className,
Class<?> classBeingRedefined, ProtectionDomain protectionDomain,
byte[] bytes) throws IllegalClassFormatException {
if (className.replace("/", ".").equals(aspectName))
return null;
Aj aj = getInstrumenter(loader);
byte[] b = aj.preProcess(className, bytes, loader);
if (Arrays.equals(bytes, b))
return null;
return b;
}
private Aj getInstrumenter(ClassLoader loader) {
if (mapFromClassLoaderToAj.containsKey(loader)) {
return mapFromClassLoaderToAj.get(loader);
}
Aj aj = new Aj(new MonitorWeavingContext(loader));
mapFromClassLoaderToAj.put(loader, aj);
return aj;
}
}
If you add "-Xbootclasspath/p:<path_to_aspects.jar>" JVM option, then you can
instrument inside the JDKs and also instrument already loaded classes.
I tried it on Java 1.6.0_15 on Mac OSX.
One little note: JVM complains about java.lang.UnsupportedOperationException:
class redefinition failed: attempted to change the schema (add/remove fields).
I suspect t has something to do with AspectJ adding extra fields. Is there a
way to force inlining of the aspects?
Best regards,
Silviu
On Nov 22, 2009, at 12:18 AM, Andy Clement wrote:
the code I posted was just an alternative way to interact with the
load time weaver. I didn't mean anything with bootclasspath.
Andy
2009/11/21 Andrica Silviu
<[email protected]<mailto:[email protected]>>:
Hi,
when you say this is an alternative way, what do you exactly mean? An
alternative way to the code I posted or an alternative way to -Xbootclasspath,
which, BTW, does not work. Crashes the JVM.
Cheers,
Silviu
On Nov 21, 2009, at 11:10 PM, Andy Clement wrote:
Glad to see you got it working.
There is an alternative way too. It involves defining a correct
weaving context that names the aspects and your options:
static class SimpleWeavingContext extends DefaultWeavingContext {
public SimpleWeavingContext(ClassLoader loader) {
super(loader);
}
@Override
public List getDefinitions(ClassLoader loader, WeavingAdaptor
adaptor) {
List definitions = new ArrayList();
Definition d = new Definition();
d.getAspectClassNames().add("MonitorAspect");
d.appendWeaverOptions("-Xjoinpoints:synchronization
-debug");
definitions.add(d);
return definitions;
}
}
and then using the ClassLoaderWeavingAdaptor:
byte[] bytes = readEntireInputStream(new
FileInputStream("bin/Test.class"));
URL[] aspects = getWeaversURL();
URL[] classpath = getClasspathURL();
URL[] realClasspath = new URL[aspects.length + classpath.length];
System.arraycopy(aspects, 0, realClasspath, 0, aspects.length);
System.arraycopy(classpath, 0, realClasspath, aspects.length,
classpath.length);
URLClassLoader myClassLoader = new URLClassLoader(realClasspath,
ClassLoader.getSystemClassLoader());
ClassLoaderWeavingAdaptor clwa = new ClassLoaderWeavingAdaptor();
clwa.initialize(myClassLoader, new
SimpleWeavingContext(myClassLoader));
byte[] newBytes = clwa.weaveClass("test.Test", bytes, true);
However, it will only work with AspectJ 1.6.7 dev builds after today
because I needed to open up initialize() so it was public rather than
protected. And I've only just committed that change.
Andy
2009/11/21 Andrica Silviu
<[email protected]<mailto:[email protected]>>:
Hi,
Indeed I forgot :) And I did create a wrapper class around the
WeavingAdaptor that sets the right permissions. The code is the following:
Please find attached the code.
It works brilliant as long as I don't instrument already loaded classes,
through java.lang.Instrumentation.instrumentation.retransformClasses(...);
or java.* classes, I don't exactly know. In this case, Java complains about
not finding the aspect. I am currently exploring the use of
-Xbootclassptah/p:<path_to_aspect>.
Thanks for the replies.
Best regards,
Silviu
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