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

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Java » Reflection » ClassLoaderScreenshots 
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;
    }
    

}

   
    
    
    
    
  
Related examples in the same category
1. Determining from Where a Class Was Loaded
2. Loading a Class That Is Not on the Classpath
3. Dynamically Reloading a Modified Class
4. Get the path from where a class is loaded
5. Using the forName() method
6. Unqualified names
7. Return the context classloader.
8. Jar Class Loader
9. Zip Class Loader
10. Various Class Loader utilities
11. Load Class
12. Load classes
13. Class Finder
14. Class For Name
15. Context ClassLoader
16. Analyze ClassLoader hierarchy for any given object or class loader
17. A class loader which loads classes using a searchlist of other classloaders
18. Equivalently to invoking Thread.currentThread().getContextClassLoader().loadClass(className); but it supports primitive types and array classes of object types or primitive types.
19. A class to simplify access to resources through the classloader
20. Get a compatible constructor for the given value type
21. Force the given class to be loaded fully.
22. does Class Exist
23. Java interpreter replacement
24. Utility to essentially do Class forName and allow configurable Classloaders.
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