org.codehaus.plexus.classworlds.realm.ClassRealm Maven / Gradle / Ivy
package org.codehaus.plexus.classworlds.realm;
/*
* Copyright 2001-2006 Codehaus Foundation.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
import java.io.IOException;
import java.io.PrintStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.Collection;
import java.util.Enumeration;
import java.util.HashSet;
import java.util.Iterator;
import java.util.SortedSet;
import java.util.TreeSet;
import org.codehaus.plexus.classworlds.ClassWorld;
import org.codehaus.plexus.classworlds.strategy.Strategy;
import org.codehaus.plexus.classworlds.strategy.StrategyFactory;
/**
* The class loading gateway. Each class realm has access to a base class loader, imports form zero or more other class
* loaders, an optional parent class loader and of course its own class path. When queried for a class/resource, a class
* realm will always query its base class loader first before it delegates to a pluggable strategy. The strategy in turn
* controls the order in which imported class loaders, the parent class loader and the realm itself are searched. The
* base class loader is assumed to be capable of loading of the bootstrap classes.
*
* @author bob mcwhirter
* @author Jason van Zyl
* @version $Id$
*/
public class ClassRealm
extends URLClassLoader
{
private ClassWorld world;
private String id;
private SortedSet foreignImports;
private SortedSet parentImports;
private Strategy strategy;
private ClassLoader parentClassLoader;
/**
* Creates a new class realm.
*
* @param world The class world this realm belongs to, must not be null.
* @param id The identifier for this realm, must not be null.
* @param baseClassLoader The base class loader for this realm, may be null to use the bootstrap class
* loader.
*/
public ClassRealm( ClassWorld world, String id, ClassLoader baseClassLoader )
{
super( new URL[0], baseClassLoader );
this.world = world;
this.id = id;
foreignImports = new TreeSet();
strategy = StrategyFactory.getStrategy( this );
}
public String getId()
{
return this.id;
}
public ClassWorld getWorld()
{
return this.world;
}
public void importFromParent( String packageName )
{
if ( parentImports == null )
{
parentImports = new TreeSet();
}
parentImports.add( new Entry( null, packageName ) );
}
boolean isImportedFromParent( String name )
{
if ( parentImports != null && !parentImports.isEmpty() )
{
for ( Iterator iterator = parentImports.iterator(); iterator.hasNext(); )
{
Entry entry = (Entry) iterator.next();
if ( entry.matches( name ) )
{
return true;
}
}
return false;
}
return true;
}
public void importFrom( String realmId, String packageName )
throws NoSuchRealmException
{
importFrom( getWorld().getRealm( realmId ), packageName );
}
public void importFrom( ClassLoader classLoader, String packageName )
{
foreignImports.add( new Entry( classLoader, packageName ) );
}
public ClassLoader getImportClassLoader( String name )
{
for ( Iterator iterator = foreignImports.iterator(); iterator.hasNext(); )
{
Entry entry = (Entry) iterator.next();
if ( entry.matches( name ) )
{
return entry.getClassLoader();
}
}
return null;
}
public Collection getImportRealms()
{
Collection importRealms = new HashSet();
for ( Iterator iterator = foreignImports.iterator(); iterator.hasNext(); )
{
Entry entry = (Entry) iterator.next();
if ( entry.getClassLoader() instanceof ClassRealm )
{
importRealms.add( entry.getClassLoader() );
}
}
return importRealms;
}
public Strategy getStrategy()
{
return strategy;
}
public void setParentClassLoader( ClassLoader parentClassLoader )
{
this.parentClassLoader = parentClassLoader;
}
public ClassLoader getParentClassLoader()
{
return parentClassLoader;
}
public void setParentRealm( ClassRealm realm )
{
this.parentClassLoader = realm;
}
public ClassRealm getParentRealm()
{
return ( parentClassLoader instanceof ClassRealm ) ? (ClassRealm) parentClassLoader : null;
}
public ClassRealm createChildRealm( String id )
throws DuplicateRealmException
{
ClassRealm childRealm = getWorld().newRealm( id, null );
childRealm.setParentRealm( this );
return childRealm;
}
public void addURL( URL url )
{
String urlStr = url.toExternalForm();
if ( urlStr.startsWith( "jar:" ) && urlStr.endsWith( "!/" ) )
{
urlStr = urlStr.substring( 4, urlStr.length() - 2 );
try
{
url = new URL( urlStr );
}
catch ( MalformedURLException e )
{
e.printStackTrace();
}
}
super.addURL( url );
}
// ----------------------------------------------------------------------
// We delegate to the Strategy here so that we can change the behavior
// of any existing ClassRealm.
// ----------------------------------------------------------------------
public Class loadClass( String name )
throws ClassNotFoundException
{
return loadClass( name, false );
}
protected synchronized Class loadClass( String name, boolean resolve )
throws ClassNotFoundException
{
try
{
// first, try loading bootstrap classes
return super.loadClass( name, resolve );
}
catch ( ClassNotFoundException e )
{
// next, try loading via imports, self and parent as controlled by strategy
return strategy.loadClass( name );
}
}
protected Class findClass( String name )
throws ClassNotFoundException
{
/*
* NOTE: This gets only called from ClassLoader.loadClass(Class, boolean) while we try to check for bootstrap
* stuff. Don't scan our class path yet, loadClassFromSelf() will do this later when called by the strategy.
*/
throw new ClassNotFoundException( name );
}
public URL findResource( String name )
{
/*
* NOTE: If this gets called from ClassLoader.getResource(String), delegate to the strategy. If this got called
* directly by other code, only scan our class path as usual for an URLClassLoader.
*/
StackTraceElement caller = new Exception().getStackTrace()[1];
if ( "java.lang.ClassLoader".equals( caller.getClassName() ) )
{
return strategy.getResource( name );
}
else
{
return super.findResource( name );
}
}
public Enumeration findResources( String name )
throws IOException
{
/*
* NOTE: If this gets called from ClassLoader.getResources(String), delegate to the strategy. If this got called
* directly by other code, only scan our class path as usual for an URLClassLoader.
*/
StackTraceElement caller = new Exception().getStackTrace()[1];
if ( "java.lang.ClassLoader".equals( caller.getClassName() ) )
{
return strategy.getResources( name );
}
else
{
return super.findResources( name );
}
}
// ----------------------------------------------------------------------------
// Display methods
// ----------------------------------------------------------------------------
public void display()
{
display( System.out );
}
public void display( PrintStream out )
{
out.println( "-----------------------------------------------------" );
for ( ClassRealm cr = this; cr != null; cr = cr.getParentRealm() )
{
out.println( "realm = " + cr.getId() );
out.println( "strategy = " + cr.getStrategy().getClass().getName() );
showUrls( cr, out );
out.println();
}
out.println( "-----------------------------------------------------" );
}
private static void showUrls( ClassRealm classRealm, PrintStream out )
{
URL[] urls = classRealm.getURLs();
for ( int i = 0; i < urls.length; i++ )
{
out.println( "urls[" + i + "] = " + urls[i] );
}
out.println( "Number of foreign imports: " + classRealm.foreignImports.size() );
for ( Iterator i = classRealm.foreignImports.iterator(); i.hasNext(); )
{
out.println( "import: " + i.next() );
}
if ( classRealm.parentImports != null )
{
out.println( "Number of parent imports: " + classRealm.parentImports.size() );
for ( Iterator i = classRealm.parentImports.iterator(); i.hasNext(); )
{
out.println( "import: " + i.next() );
}
}
}
public String toString()
{
return "ClassRealm[" + getId() + ", parent: " + getParentClassLoader() + "]";
}
//---------------------------------------------------------------------------------------------
// Search methods that can be ordered by strategies to load a class
//---------------------------------------------------------------------------------------------
public Class loadClassFromImport( String name )
{
ClassLoader importClassLoader = getImportClassLoader( name );
if ( importClassLoader != null )
{
try
{
return importClassLoader.loadClass( name );
}
catch ( ClassNotFoundException e )
{
return null;
}
}
return null;
}
public Class loadClassFromSelf( String name )
{
Class clazz;
try
{
clazz = findLoadedClass( name );
if ( clazz == null )
{
clazz = super.findClass( name );
}
}
catch ( ClassNotFoundException e )
{
return null;
}
return clazz;
}
public Class loadClassFromParent( String name )
{
ClassLoader parent = getParentClassLoader();
if ( parent != null && isImportedFromParent( name ) )
{
try
{
return parent.loadClass( name );
}
catch ( ClassNotFoundException e )
{
return null;
}
}
return null;
}
//---------------------------------------------------------------------------------------------
// Search methods that can be ordered by strategies to get a resource
//---------------------------------------------------------------------------------------------
public URL loadResourceFromImport( String name )
{
ClassLoader importClassLoader = getImportClassLoader( name );
if ( importClassLoader != null )
{
return importClassLoader.getResource( name );
}
return null;
}
public URL loadResourceFromSelf( String name )
{
return super.findResource( name );
}
public URL loadResourceFromParent( String name )
{
ClassLoader parent = getParentClassLoader();
if ( parent != null && isImportedFromParent( name ) )
{
return parent.getResource( name );
}
else
{
return null;
}
}
//---------------------------------------------------------------------------------------------
// Search methods that can be ordered by strategies to get resources
//---------------------------------------------------------------------------------------------
public Enumeration loadResourcesFromImport( String name )
{
ClassLoader importClassLoader = getImportClassLoader( name );
if ( importClassLoader != null )
{
try
{
return importClassLoader.getResources( name );
}
catch ( IOException e )
{
return null;
}
}
return null;
}
public Enumeration loadResourcesFromSelf( String name )
{
try
{
return super.findResources( name );
}
catch ( IOException e )
{
return null;
}
}
public Enumeration loadResourcesFromParent( String name )
{
ClassLoader parent = getParentClassLoader();
if ( parent != null && isImportedFromParent( name ) )
{
try
{
return parent.getResources( name );
}
catch ( IOException e )
{
// eat it
}
}
return null;
}
}
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