Load class from Thread's ContextClassLoader, classloader of derived class or the system ClassLoader : ClassLoader « Reflection « Java

1. Java
2. Reflection
3. ClassLoader

Load class from Thread's ContextClassLoader, classloader of derived class or the system ClassLoader

      
// 
// Copyright 2004-2005 Mort Bay Consulting Pty. Ltd.
// ------------------------------------------------------------------------
// 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.net.URL;
import java.util.Locale;
import java.util.MissingResourceException;
import java.util.ResourceBundle;

/* ------------------------------------------------------------ */
/** 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>          
 * @author Greg Wilkins (gregw)
 */
public class Loader
{
    /* ------------------------------------------------------------ */
    public static URL getResource(Class loadClass,String name, boolean checkParents)
        throws ClassNotFoundException
    {
        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;
    }

    /* ------------------------------------------------------------ */
    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
     */
    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;
    }
    

}

   
    
    
    
    
    
  

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