/**
* Copyright (c) 2000-2009, Jasig, Inc.
* See license distributed with this file and available online at
* https://www.ja-sig.org/svn/jasig-parent/tags/rel-10/license-header.txt
*/
package org.jasig.portal.car;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.security.AccessController;
import java.security.PrivilegedActionException;
import java.security.PrivilegedExceptionAction;
import java.security.SecureClassLoader;
import java.util.StringTokenizer;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
/**
* Loads classes and resources from installed CARs via the CarResources class.
* If classes are visible via the parent class loader then they will be used
* in place of those in the CARs. This is a singleton so that we have a single
* unified class namespace for all car resources preventing linkage errors and
* class cast exceptions.
* @author Mark Boyd {@link <a href="mailto:mark.boyd@engineer.com">mark.boyd@engineer.com</a>}
* @version $Revision: 45149 $
*/
public class CarClassLoader
extends SecureClassLoader
{
public final static String RCS_ID = "@(#) $Header$";
private static final Log log = LogFactory.getLog(CarClassLoader.class);
private final CarResources carResources;
/**
Create a CarClassloader with the indicated parent class loader. See
comment for zero parameter constructor for description of package scoping.
*/
CarClassLoader( CarResources carResources )
{
super( carResources.getClass().getClassLoader() );
this.carResources = carResources;
}
/**
Implement the overloading of findClass to return classes that are
available from installed CAR files. Class loading precedes with the
parent classloader first which delegates to this class loader if the
classes aren't found.
*/
public Class findClass( final String name )
throws ClassNotFoundException
{
PrivilegedExceptionAction action = new PrivilegedExceptionAction()
{
public Object run()
throws ClassNotFoundException
{
byte[] buf = null;
String pkgName = getPackageName(name);
InputStream in = null;
try
{
String file = name.replace( '.', '/' ) + ".class";
CarResources crs = CarResources.getInstance();
int size = (int) crs.getResourceSize( file );
in = crs.getResourceAsStream( file );
if ( in == null || size == -1 )
throw new Exception( "Car resource " +
file + " not found." );
buf = new byte[size];
int offSet = 0;
int totalRead = 0;
int bytesRead = 0;
int remaining = size;
while( totalRead < size )
{
bytesRead = in.read( buf, offSet, remaining );
remaining -= bytesRead;
offSet += bytesRead;
totalRead += bytesRead;
}
}
catch( Exception e )
{
throw new ClassNotFoundException( name,
e );
} finally {
try {
if (in != null) {
in.close();
}
} catch (IOException ioe) {
log.error(
"CarClassLoader::findClass() Could not close inputStream "
+ ioe);
}
}
// package must be defined prior to defined
// the class.
createPackage( pkgName );
return defineTheClass( name, buf, 0, buf.length);
}
};
try
{
return ( Class ) AccessController.doPrivileged( action );
}
catch( PrivilegedActionException pae )
{
throw (ClassNotFoundException) pae.getException();
}
}
/**
Create and return the Class object from the passed in class bytes. This
code enables the inner class used in findClass() to call into the
superclass's defineClass method. It has protected scope in the
superclass and hence is not visible to an innner class but is visible
to this class.
*/
private Class defineTheClass( String n, byte[] b, int offset, int len )
{
return super.defineClass( n, b, offset, len );
}
/**
* Creates the package name for the calling class, which is null
* by default based on the JavaDoc for ClassLoader. The package
* must be created prior to defining the Class.
*
* @param pkgName the package to create.
**/
private void createPackage(String pkgName)
{
// package must be defined before the class
// according to the API docs.
try
{
if ( null != pkgName && null == getPackage(pkgName))
definePackage( pkgName, "", "", "", "", "", "", null );
}
catch( IllegalArgumentException iae )
{
// do nothing, assume a synchronization issue
// where one thread had set it prior to another
// doing so.. small window, but could happen.
}
}
/**
* Returns a package name from a package/classname path. If the
* package is not available (default package), then null is
* returned.
*
* @param name the package/class name.
* @return the package name (dot notation) or null if not found
*/
private String getPackageName( String name )
{
if ( name.indexOf(".") != -1 )
{
StringBuffer sb = new StringBuffer();
StringTokenizer st = new StringTokenizer(name,".");
int tokens = st.countTokens();
int count = 1;
while(st.hasMoreTokens())
{
if ( count < tokens )
{
sb.append(st.nextToken());
if ( count != (tokens-1) )
sb.append(".");
}
else
break;
count++;
}
return sb.toString();
}
else
return null;
}
/**
Returns a URL pointing to a car resource if a suitable resource is
found in the loaded set of CAR files or null if one is not found.
*/
public URL findResource( String res )
{
return this.carResources.findResource( res );
}
}
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