[jboss-user] [EJB 3.0] - Solution for Lazy proxy class leak
Hi,
It is a known problem that 4.0.4 and EJB-3 leaks Hibernate lazy proxy classes generated by
Javassist. The cache introduced in Javassist-3.4 (4.0.4 ships with Javassist-3.2) should
solve the problem, but unfortunately doesn't. Probably because Hibernate uses a
different MethodHandler for each new proxy and so you get a cache miss.
However it is possible to use Javassist-3.4 and supply a custom ClassLoaderProvider
instance. It is important that this provide creates a new CL instance that just delegates.
So the CL can be collected (and so can the proxy). Here is how to do that. The code can be
put into a service mbean:
| ProxyFactory.useCache = false;
| ProxyFactory.classLoaderProvider = new ClassLoaderProvider() {
| public ClassLoader get(ProxyFactory pf) {
| ClassLoader parent = getClassLoader(pf);
| ClassLoader cl = new ClassLoader(parent) {
| @Override
| public Class loadClass(final String className) throws
ClassNotFoundException {
| try {
| return super.loadClass(className);
| } catch (ClassNotFoundException e) {
| // only allow loading of ProxyObject from this loader
| if (className.equals(ProxyObject.class.getName())) {
| return
ProxyObject.class.getClassLoader().loadClass(className);
| }
| // was some other classname, throw the CNFE
| throw e;
| }
| }
| };
| return cl;
| }
|
| private ClassLoader getClassLoader(ProxyFactory pf) {
| Class superClass = pf.getSuperclass();
| Class[] interfaces = pf.getInterfaces();
| ClassLoader loader = null;
| if (superClass != null &&
!superClass.getName().equals("java.lang.Object"))
| loader = superClass.getClassLoader();
| else if (interfaces != null && interfaces.length > 0)
| loader = interfaces[0].getClassLoader();
|
| if (loader == null) {
| loader = getClass().getClassLoader();
| // In case javassist is in the endorsed dir
| if (loader == null) {
| loader = Thread.currentThread().getContextClassLoader();
| if (loader == null)
| loader = ClassLoader.getSystemClassLoader();
| }
| }
|
| return loader;
| }
|
| };
|
I don't know if this leak is fixed in later JBoss versions.
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