| HeirarchicalLoaderRepository3.java |
/*
* JBoss, the OpenSource J2EE webOS
*
* Distributable under LGPL license.
* See terms of license at gnu.org.
*/
package org.jboss.mx.loading;
import java.net.URL;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.Iterator;
import java.util.List;
import java.util.Set;
import javax.management.AttributeNotFoundException;
import javax.management.InstanceNotFoundException;
import javax.management.MBeanException;
import javax.management.MBeanServer;
import javax.management.ObjectName;
import javax.management.ReflectionException;
import org.jboss.logging.Logger;
import org.jboss.mx.loading.LoadMgr3.PkgClassLoader;
import org.jboss.mx.server.ServerConstants;
/** A simple extension of UnifiedLoaderRepository3 that adds the notion of a
* parent UnifiedLoaderRepository. Classes and resources are loaded from child
* first and then the parent depending on the java2ParentDelegation flag.
*
* @author Scott.Stark@jboss.org
* @version $Revision: 1.11.4.1 $
*/
public class HeirarchicalLoaderRepository3 extends UnifiedLoaderRepository3
{
// Attributes ----------------------------------------------------
private static final Logger log = Logger.getLogger(HeirarchicalLoaderRepository3.class);
private static ObjectName DEFAULT_LOADER_NAME;
static
{
try
{
DEFAULT_LOADER_NAME = new ObjectName(ServerConstants.DEFAULT_LOADER_NAME);
}
catch(Exception e)
{
log.error("Failed to initialize default loader name", e);
}
}
/** A ClassLoader override that prevents a child class loader from looking
* beyond its URLs for classes.
*/
static class NoParentClassLoader extends ClassLoader
{
NoParentClassLoader()
{
super(HeirarchicalLoaderRepository3.class.getClassLoader());
}
/** Override to always return null to force the UCL to only load from
* its URLs.
* @param name
* @return
*/
public URL getResource(String name)
{
return null;
}
/** Override to always throw a CNFE to force the UCL to only load from
* its URLs.
* @param name
* @param resolve
* @return nothing
* @throws ClassNotFoundException always
*/
protected synchronized Class loadClass(String name, boolean resolve)
throws ClassNotFoundException
{
throw new ClassNotFoundException("NoParentClassLoader has no classes");
}
/** Override to always throw a CNFE to force the UCL to only load from
* its URLs.
* @param name
* @return
* @throws ClassNotFoundException
*/
protected Class findClass(String name) throws ClassNotFoundException
{
throw new ClassNotFoundException("NoParentClassLoader has no classes");
}
}
static class CacheClassLoader extends UnifiedClassLoader3
{
Class cacheClass;
CacheClassLoader(Class cacheClass, LoaderRepository rep)
{
super(null, null, new NoParentClassLoader(), rep);
this.cacheClass = cacheClass;
}
protected Class findClass(String name) throws ClassNotFoundException
{
Class c = cacheClass;
if( name.equals(cacheClass.getName()) == false )
c = null;
return c;
}
}
/** The repository to which we delegate if requested classes or resources
are not available from this repository.
*/
private UnifiedLoaderRepository3 parentRepository;
/** A flag indicating if the standard parent delegation loading where the
parent repository is used before this repository.
*/
private boolean java2ParentDelegation;
/** Create a HeirarchicalLoaderRepository3 with an explicit parent.
*
* @param parent
* @throws AttributeNotFoundException
* @throws InstanceNotFoundException
* @throws MBeanException
* @throws ReflectionException
*/
public HeirarchicalLoaderRepository3(UnifiedLoaderRepository3 parent)
throws AttributeNotFoundException, InstanceNotFoundException, MBeanException, ReflectionException
{
this.parentRepository = parent;
}
/** Create a HeirarchicalLoaderRepository3 with a parent obtained by querying
* the server for the ServerConstants.DEFAULT_LOADER_NAME mbean.
*
* @param server
* @throws AttributeNotFoundException
* @throws InstanceNotFoundException
* @throws MBeanException
* @throws ReflectionException
*/
public HeirarchicalLoaderRepository3(MBeanServer server)
throws AttributeNotFoundException, InstanceNotFoundException, MBeanException, ReflectionException
{
this(server, DEFAULT_LOADER_NAME);
}
/** Create a HeirarchicalLoaderRepository3 with a parent obtained by querying
* the server for the parentName mbean.
*
* @param server
* @param parentName
* @throws AttributeNotFoundException
* @throws InstanceNotFoundException
* @throws MBeanException
* @throws ReflectionException
*/
public HeirarchicalLoaderRepository3(MBeanServer server, ObjectName parentName)
throws AttributeNotFoundException, InstanceNotFoundException, MBeanException, ReflectionException
{
this.parentRepository = (UnifiedLoaderRepository3) server.getAttribute(parentName,
"Instance");
}
// Public --------------------------------------------------------
public RepositoryClassLoader newClassLoader(final URL url, boolean addToRepository)
throws Exception
{
UnifiedClassLoader3 ucl = null;
if( java2ParentDelegation == false )
ucl = new UnifiedClassLoader3(url, null, new NoParentClassLoader(), this);
else
ucl = new UnifiedClassLoader3(url, null, this);
if( addToRepository )
{
this.addClassLoader(ucl);
}
return ucl;
}
public RepositoryClassLoader newClassLoader(final URL url, final URL origURL, boolean addToRepository)
throws Exception
{
UnifiedClassLoader3 ucl = null;
if( java2ParentDelegation == false )
ucl = new UnifiedClassLoader3(url, origURL, new NoParentClassLoader(), this);
else
ucl = new UnifiedClassLoader3(url, origURL, this);
if( addToRepository )
{
this.addClassLoader(ucl);
}
return ucl;
}
/** Get the use parent first flag. This indicates whether the parent
* repository is consulted first for resource and class loading or if the
* HeirchicalLoaderRepository is consulted first.
*
* @return true if the parent repository is consulted first, false if the
* HeirchicalLoaderRepository is consulted first.
*/
public boolean getUseParentFirst()
{
return java2ParentDelegation;
}
/** Set the use parent first flag. This indicates whether the parent
* repository is consulted first for resource and class loading or if the
* HeirchicalLoaderRepository is consulted first.
*
* @param flag true if the parent repository is consulted first, false if the
* HeirchicalLoaderRepository is consulted first.
*/
public void setUseParentFirst(boolean flag)
{
java2ParentDelegation = flag;
}
/** Load a class using the repository class loaders.
*
* @param name The name of the class
* @param resolve an obsolete unused parameter from ClassLoader.loadClass
* @param scl The asking class loader
* @return The loaded class
* @throws ClassNotFoundException If the class could not be found.
*/
public Class loadClass(String name, boolean resolve, ClassLoader scl)
throws ClassNotFoundException
{
Class foundClass = null;
if( java2ParentDelegation == true )
{
try
{
// Try the parent repository first
foundClass = parentRepository.loadClass(name, resolve, scl);
}
catch(ClassNotFoundException e)
{
// Next try our repository
if( foundClass == null )
foundClass = super.loadClass(name, resolve, scl);
}
}
else
{
try
{
// Try this repository first
foundClass = super.loadClass(name, resolve, scl);
}
catch(ClassNotFoundException e)
{
// Next try our parent repository
if( foundClass == null )
foundClass = parentRepository.loadClass(name, resolve, scl);
}
}
if( foundClass != null )
return foundClass;
/* If we reach here, all of the classloaders currently in the VM don't
know about the class
*/
throw new ClassNotFoundException(name);
}
/** Override getCachedClass to return the parent repository cached class
* if java2ParentDelegation=true, followed by this repository's cached
* value. Else, if java2ParentDelegation=false, only check this repository's
* cache to attempt to load the class from the child repository before
* going to the parent cache.
*
* @param classname
* @return the cached class if found, null otherwise
*/
public Class getCachedClass(String classname)
{
Class clazz = null;
if( java2ParentDelegation == true )
{
// Try the parent repository
clazz = parentRepository.getCachedClass(classname);
// Next try our parent repository
if( clazz == null )
clazz = super.getCachedClass(classname);
}
else
{
// Try this repository
clazz = super.getCachedClass(classname);
}
return clazz;
}
/** Find a resource from this repository. This first looks to this
* repository and then the parent repository.
* @param name The name of the resource
* @param scl The asking class loader
* @return An URL for reading the resource, or <code>null</code> if the
* resource could not be found.
*/
public URL getResource(String name, ClassLoader scl)
{
URL resource = null;
if( java2ParentDelegation == true )
{
/* Try our parent repository. This cannot use the getResource method
because we do not want the parent repository to load the resource via
our scoped class loader
*/
resource = getParentResource(name, scl);
// Next try this repository
if( resource == null )
resource = super.getResource(name, scl);
}
else
{
// Try this repository
resource = super.getResource(name, scl);
// Next try our parent repository
if( resource == null )
{
/* Try our parent repository. This cannot use the getResource method
because we do not want the parent repository to load the resource via
our scoped class loader
*/
resource = getParentResource(name, scl);
}
}
return resource;
}
/** Find all resource URLs for the given name. This is entails an
* exhuastive search of this and the parent repository and is an expensive
* operation.
*
* @param name the resource name
* @param cl the requesting class loader
* @param urls a list into which the located resource URLs will be placed
*/
public void getResources(String name, ClassLoader cl, List urls)
{
if( java2ParentDelegation == true )
{
// Get the parent repository resources
parentRepository.getResources(name, cl, urls);
// Next get this repositories resources
super.getResources(name, cl, urls);
}
else
{
// Get this repositories resources
super.getResources(name, cl, urls);
// Next get the parent repository resources
parentRepository.getResources(name, cl, urls);
}
}
/** Obtain a listing of the URLs for all UnifiedClassLoaders associated with
*the repository
*/
public URL[] getURLs()
{
URL[] ourURLs = super.getURLs();
URL[] parentURLs = parentRepository.getURLs();
int size = ourURLs.length + parentURLs.length;
URL[] urls = new URL[size];
System.arraycopy(ourURLs, 0, urls, 0, ourURLs.length);
System.arraycopy(parentURLs, 0, urls, ourURLs.length, parentURLs.length);
return urls;
}
/** Called by LoadMgr to locate a previously loaded class. This looks
* first to this repository and then the parent repository.
*@return the cached class if found, null otherwise
*/
public Class loadClassFromCache(String name)
{
Class foundClass = null;
if( java2ParentDelegation == true )
{
// Try this repository
foundClass = parentRepository.loadClassFromCache(name);
// Next try our parent repository
if( foundClass == null )
foundClass = super.loadClassFromCache(name);
}
else
{
// Try this repository
foundClass = super.loadClassFromCache(name);
/* We do not try the parent repository cache as this does not allow
the child repository to override classes in the parent
*/
}
return foundClass;
}
/** Called by LoadMgr to obtain all class loaders. This returns a set of
* PkgClassLoader with the HeirarchicalLoaderRepository3 ordered ahead of
* the parent repository pkg class loaders
*@return Set<PkgClassLoader>
*/
public Set getPackageClassLoaders(String name)
{
Set pkgSet = super.getPackageClassLoaders(name);
Set parentPkgSet = parentRepository.getPackageClassLoaders(name);
GetClassLoadersAction action = new GetClassLoadersAction(name, pkgSet,
parentPkgSet);
Set theSet = (Set) AccessController.doPrivileged(action);
return theSet;
}
public int compare(LoaderRepository lr)
{
if (lr == this)
return 0;
return reverseCompare(lr);
}
protected int reverseCompare(LoaderRepository lr)
{
// If it is not our parent we don't care
if (lr != parentRepository)
return 0;
// The order depends upon the delegation model
if (java2ParentDelegation)
return +1;
else
return -1;
}
/** A subset of the functionality found in getResource(String, ClassLoader),
* but this version queries the parentRepository and does not use the scl
* to avoid leaking class loaders across scoped.
*
* @param name - the resource name
* @param scl - the requesting class loader
* @return the resource URL if found, null otherwise
*/
private URL getParentResource(String name, ClassLoader scl)
{
// Not found in classloader, ask the global cache
URL resource = parentRepository.getResourceFromGlobalCache(name);
// The cache has it, we are done
if( resource != null )
return resource;
// Not visible in global cache, iterate on all classloaders
resource = parentRepository.getResourceFromRepository(name, scl);
return resource;
}
private class GetClassLoadersAction implements PrivilegedAction
{
private String name;
Set pkgSet;
Set parentPkgSet;
GetClassLoadersAction(String name, Set pkgSet, Set parentPkgSet)
{
this.name = name;
this.pkgSet = pkgSet;
this.parentPkgSet = parentPkgSet;
}
public Object run()
{
// Build a set of PkgClassLoader
Set theSet = ClassLoaderUtils.newPackageSet();
if( pkgSet != null )
{
Iterator iter = pkgSet.iterator();
while( iter.hasNext() )
{
RepositoryClassLoader ucl = (RepositoryClassLoader) iter.next();
PkgClassLoader pkgUcl = new PkgClassLoader(ucl, 0);
theSet.add(pkgUcl);
}
}
if( java2ParentDelegation == false )
{
Class cacheClass = parentRepository.loadClassFromCache(name);
if( cacheClass != null )
{
RepositoryClassLoader ucl = new CacheClassLoader(cacheClass, HeirarchicalLoaderRepository3.this);
PkgClassLoader pkgUcl = new PkgClassLoader(ucl, 1);
theSet.add(pkgUcl);
}
}
if( parentPkgSet != null )
{
Iterator iter = parentPkgSet.iterator();
while( iter.hasNext() )
{
RepositoryClassLoader ucl = (RepositoryClassLoader) iter.next();
PkgClassLoader pkgUcl = new PkgClassLoader(ucl, 2);
theSet.add(pkgUcl);
}
}
if( java2ParentDelegation == false )
{
// Include a class loader with a parent to the system class loader
ClassLoader loader = RepositoryClassLoader.class.getClassLoader();
RepositoryClassLoader ucl = null;
if( loader instanceof RepositoryClassLoader )
ucl = (RepositoryClassLoader) loader;
else
ucl = new UnifiedClassLoader3(null, null, HeirarchicalLoaderRepository3.this);
PkgClassLoader pkgUcl = new PkgClassLoader(ucl, 3);
theSet.add(pkgUcl);
}
return theSet;
}
}
}
| HeirarchicalLoaderRepository3.java |