src/java/org/eclipse/jetty/util/Loader.java

//
//  ========================================================================
//  Copyright (c) 1995-2014 Mort Bay Consulting Pty. Ltd.
//  ------------------------------------------------------------------------
//  All rights reserved. This program and the accompanying materials
//  are made available under the terms of the Eclipse Public License v1.0
//  and Apache License v2.0 which accompanies this distribution.
//
//      The Eclipse Public License is available at
//      http://www.eclipse.org/legal/epl-v10.html
//
//      The Apache License v2.0 is available at
//      http://www.opensource.org/licenses/apache2.0.php
//
//  You may elect to redistribute this code under either of these licenses.
//  ========================================================================
//

package org.eclipse.jetty.util;

import java.io.File;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.Locale;
import java.util.MissingResourceException;
import java.util.ResourceBundle;

import org.eclipse.jetty.util.resource.Resource;

/* ------------------------------------------------------------ */
/** ClassLoader Helper.
 * This helper class allows classes to be loaded either from the
 * Thread's ContextClassLoader, the classloader of the derived class
 * or the system ClassLoader.
 *
 * <B>Usage:</B><PRE>
 * public class MyClass {
 *     void myMethod() {
 *          ...
 *          Class c=Loader.loadClass(this.getClass(),classname);
 *          ...
 *     }
 * </PRE>          
 * 
 */
public class Loader
{
    /* ------------------------------------------------------------ */
    public static URL getResource(Class<?> loadClass,String name, boolean checkParents)
    {
        URL url =null;
        ClassLoader loader=Thread.currentThread().getContextClassLoader();
        while (url==null && loader!=null )
        {
            url=loader.getResource(name); 
            loader=(url==null&&checkParents)?loader.getParent():null;
        }      
        
        loader=loadClass==null?null:loadClass.getClassLoader();
        while (url==null && loader!=null )
        {
            url=loader.getResource(name); 
            loader=(url==null&&checkParents)?loader.getParent():null;
        }       

        if (url==null)
        {
            url=ClassLoader.getSystemResource(name);
        }   

        return url;
    }

    /* ------------------------------------------------------------ */
    @SuppressWarnings("rawtypes")
    public static Class loadClass(Class loadClass,String name)
        throws ClassNotFoundException
    {
        return loadClass(loadClass,name,false);
    }
    
    /* ------------------------------------------------------------ */
    /** Load a class.
     * 
     * @param loadClass
     * @param name
     * @param checkParents If true, try loading directly from parent classloaders.
     * @return Class
     * @throws ClassNotFoundException
     */
    @SuppressWarnings("rawtypes")
    public static Class loadClass(Class loadClass,String name,boolean checkParents)
        throws ClassNotFoundException
    {
        ClassNotFoundException ex=null;
        Class<?> c =null;
        ClassLoader loader=Thread.currentThread().getContextClassLoader();
        while (c==null && loader!=null )
        {
            try { c=loader.loadClass(name); }
            catch (ClassNotFoundException e) {if(ex==null)ex=e;}
            loader=(c==null&&checkParents)?loader.getParent():null;
        }      
        
        loader=loadClass==null?null:loadClass.getClassLoader();
        while (c==null && loader!=null )
        {
            try { c=loader.loadClass(name); }
            catch (ClassNotFoundException e) {if(ex==null)ex=e;}
            loader=(c==null&&checkParents)?loader.getParent():null;
        }       

        if (c==null)
        {
            try { c=Class.forName(name); }
            catch (ClassNotFoundException e) {if(ex==null)ex=e;}
        }   

        if (c!=null)
            return c;
        throw ex;
    }
    
    
    
    /* ------------------------------------------------------------ */
    public static ResourceBundle getResourceBundle(Class<?> loadClass,String name,boolean checkParents, Locale locale)
        throws MissingResourceException
    {
        MissingResourceException ex=null;
        ResourceBundle bundle =null;
        ClassLoader loader=Thread.currentThread().getContextClassLoader();
        while (bundle==null && loader!=null )
        {
            try { bundle=ResourceBundle.getBundle(name, locale, loader); }
            catch (MissingResourceException e) {if(ex==null)ex=e;}
            loader=(bundle==null&&checkParents)?loader.getParent():null;
        }      
        
        loader=loadClass==null?null:loadClass.getClassLoader();
        while (bundle==null && loader!=null )
        {
            try { bundle=ResourceBundle.getBundle(name, locale, loader); }
            catch (MissingResourceException e) {if(ex==null)ex=e;}
            loader=(bundle==null&&checkParents)?loader.getParent():null;
        }       

        if (bundle==null)
        {
            try { bundle=ResourceBundle.getBundle(name, locale); }
            catch (MissingResourceException e) {if(ex==null)ex=e;}
        }   

        if (bundle!=null)
            return bundle;
        throw ex;
    }
    
    
    /* ------------------------------------------------------------ */
    /**
     * Generate the classpath (as a string) of all classloaders
     * above the given classloader.
     * 
     * This is primarily used for jasper.
     * @return the system class path
     */
    public static String getClassPath(ClassLoader loader) throws Exception
    {
        StringBuilder classpath=new StringBuilder();
        while (loader != null && (loader instanceof URLClassLoader))
        {
            URL[] urls = ((URLClassLoader)loader).getURLs();
            if (urls != null)
            {     
                for (int i=0;i<urls.length;i++)
                {
                    Resource resource = Resource.newResource(urls[i]);
                    File file=resource.getFile();
                    if (file!=null && file.exists())
                    {
                        if (classpath.length()>0)
                            classpath.append(File.pathSeparatorChar);
                        classpath.append(file.getAbsolutePath());
                    }
                }
            }
            loader = loader.getParent();
        }
        return classpath.toString();
    }
}