/*!
* This program is free software; you can redistribute it and/or modify it under the
* terms of the GNU Lesser General Public License, version 2.1 as published by the Free Software
* Foundation.
*
* You should have received a copy of the GNU Lesser General Public License along with this
* program; if not, you can obtain a copy at http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html
* or from the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*
* This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
* without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
* See the GNU Lesser General Public License for more details.
*
* Copyright (c) 2002-2013 Pentaho Corporation.. All rights reserved.
*/
package org.pentaho.platform.plugin.services.pluginmgr;
import org.apache.commons.io.filefilter.WildcardFileFilter;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.pentaho.platform.engine.services.messages.Messages;
import java.io.File;
import java.io.FilenameFilter;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLClassLoader;
import java.text.MessageFormat;
import java.util.ArrayList;
import java.util.List;
/**
* A custom implementation of {@link URLClassLoader} for Pentaho Platform Plugins. It is used to load plugin jars and
* classes and aids in retrieving resources by providing a root directory to search for resources related to plugins.
* <p>
* Note: {@link PluginClassLoader} will search for jar files in a 'lib' subdirectory under the pluginDir provided in the
* constructor. Class and other resources will be visible to this classloader in either the root directory of the plugin
* or in the lib folder.
*
* @author aphillips
*/
public class PluginClassLoader extends URLClassLoader {
private static Log log = LogFactory.getLog( PluginClassLoader.class );
private File pluginDir;
private boolean overrideLoad = false;
/**
* Creates a class loader for loading plugin classes and discovering resources. Jars must be located in
* [pluginDir]/lib.
*
* @param pluginDir
* the root directory of the plugin
* @param parent
* the parent classloader
*/
public PluginClassLoader( final File pluginDir, ClassLoader parent ) {
super( getPluginUrls( pluginDir ), parent );
this.pluginDir = pluginDir;
if ( log.isDebugEnabled() ) {
log.debug( "URLs for this classloader:" ); //$NON-NLS-1$
for ( URL url : getURLs() ) {
log.debug( url );
}
}
}
/**
* Convenience method that creates a {@link PluginClassLoader} with the current classloader as it's parent.
*
* @param pluginDir
* the root directory of the plugin
* @param o
* the object from which the parent classloader will be derived
*/
public PluginClassLoader( final File pluginDir, Object o ) {
this( pluginDir, o.getClass().getClassLoader() );
}
/**
* Controls whether or not this classloader will eagerly load a class requested by {@link #loadClass(String, boolean)}
* ahead of the parent classloader. or delegate the load to the parent. If this method is not called, the default
* behavior will apply which is to *not* override classloading.
*
* @param b
* if true, loadClass method will look to this loader first to load a class, otherwise, the parent
* classloader will be queried first.
*/
public void setOverrideLoad( boolean b ) {
overrideLoad = b;
if ( b ) {
log.debug( "classloader " + this + " is set to override mode. loadClass will now attempt to load " //$NON-NLS-1$ //$NON-NLS-2$
+ "the class from the classpath known to this classloader before delegating to the parent classloader" ); //$NON-NLS-1$
}
}
protected static URL[] getPluginUrls( File pluginDir ) {
List<URL> urls = new ArrayList<URL>();
File libDir = new File( pluginDir, "lib" ); //$NON-NLS-1$
try {
urls.add( pluginDir.toURI().toURL() );
urls.add( libDir.toURI().toURL() );
} catch ( MalformedURLException e ) {
log.warn( Messages.getInstance().getString(
"PluginClassLoader.WARN_FAILED_TO_ADD_PLUGIN_DIR_TO_CLASSPATH", pluginDir //$NON-NLS-1$
.getAbsolutePath(), libDir.getAbsolutePath() ), e );
}
addJars( urls, libDir );
return urls.toArray( new URL[urls.size()] );
}
protected static void addJars( List<URL> urls, File folder ) {
if ( folder.exists() && folder.isDirectory() ) {
// get a list of all the JAR files
FilenameFilter filter = new WildcardFileFilter( "*.jar" ); //$NON-NLS-1$
File[] jarFiles = folder.listFiles( filter );
if ( jarFiles != null && jarFiles.length > 0 ) {
for ( File file : jarFiles ) {
URL url = null;
try {
url = file.toURI().toURL();
if ( log.isDebugEnabled() ) {
log.debug( "adding jar to plugin classloader: " + url.toString() ); //$NON-NLS-1$
}
urls.add( url );
} catch ( MalformedURLException e ) {
log.warn( MessageFormat.format( "PluginClassLoader.WARN_FAILED_TO_ADD_JAR_TO_CLASSPATH", file //$NON-NLS-1$
.getAbsolutePath() ), e );
}
}
}
}
}
public File getPluginDir() {
return pluginDir;
}
@Override
public Class<?> loadClass( String name, boolean resolve ) throws ClassNotFoundException {
if ( log.isDebugEnabled() ) {
log.debug( "loadClass(" + name + ")... " ); //$NON-NLS-1$ //$NON-NLS-2$
}
Class<?> t = null;
/*
* Here we check the cache to see if the class has been loaded before by either this or the parent classloader. If
* it has, then there is no need to load the class again, just return it.
*/
t = findLoadedClass( name );
if ( t != null ) {
if ( log.isDebugEnabled() ) {
log.debug( MessageFormat.format( "{0} loaded by {1}", name, t.getClassLoader() ) ); //$NON-NLS-1$
}
return t;
}
/*
* If we are overriding the parent classloader we will first try to load this class from this classloader object in
* isolation (no awareness of the parent classloader). If this classloader does not have the class, we will proceed
* to attempt to load the class from the parent.
*/
if ( overrideLoad ) {
try {
t = findClass( name );
if ( t != null ) {
if ( log.isDebugEnabled() ) {
log.debug( MessageFormat.format( "{0} loaded by {1}", name, this ) ); //$NON-NLS-1$
}
if ( resolve ) {
resolveClass( t );
}
return t;
}
} catch ( ClassNotFoundException e ) {
if ( log.isTraceEnabled() ) {
log.trace( MessageFormat.format( "class {0} not found in loader {1}. Trying parent loader", name, this ) ); //$NON-NLS-1$
}
}
}
/*
* At this point we have not found the class either in the cache or in this classloader, so we need to ask the
* parent.
*/
t = super.loadClass( name, resolve );
if ( log.isDebugEnabled() ) {
log.debug( MessageFormat.format( "{0} loaded by {1}", name, t.getClassLoader() ) ); //$NON-NLS-1$
}
return t;
}
@Override
public String toString() {
return super.toString() + ( ( pluginDir != null ) ? " at " + pluginDir.getAbsolutePath() : "" ); //$NON-NLS-1$ //$NON-NLS-2$
}
}