webworkclassloader.java

webwork source

package webwork.util.classloader;

import java.security.*;
import java.net.URL;
import java.net.MalformedURLException;
import java.io.*;
import java.util.*;

/**
 * @author Hani Suleiman ([e-mail])
 * Date: Oct 19 2003
 * Time: 11:16:12 PM
 */
public abstract class WebworkClassLoader extends SecureClassLoader implements Cloneable
{
  protected String[] packages = null;
  private Map cache = new HashMap();

  protected WebworkClassLoader()
  {
    this(ClassLoader.getSystemClassLoader());
  }

  protected WebworkClassLoader(ClassLoader parent)
  {
    super(parent);
  }

  public void setPackages(String[] p)
  {
    this.packages = p;
  }

  protected synchronized Class loadClass(String name, boolean resolve) throws ClassNotFoundException
  {
    Class c = (Class)cache.get(name);
    if(c!=null) return c;
    boolean handles = false;
    if(packages!=null)
    {
      for(int i = 0; i < packages.length; i++)
      {
        if(name.startsWith(packages[i]))
        {
          handles = true;
          break;
        }
      }
    }
    if(!handles)
    {
      return super.loadClass(name, resolve);
    }
    try
    {
      c = findClass(name);
    }
    catch(ClassNotFoundException ex)
    {
      return super.loadClass(name, resolve);
    }
    cache.put(name, c);
    return c;
  }

  protected Class findClass(String name) throws ClassNotFoundException
  {
    String path = name.replace('.', '/').concat(".class");
    byte[] data = getFile(path);
    if(data == null)
      throw new ClassNotFoundException();

    return defineClass(name, data, 0, data.length);
  }

  protected URL findResource(String name)
  {
    byte[] data = this.getFile(name);

    if(data == null)
      return null;
    try
    {
      return getDataURL(name, data);
    }
    catch(MalformedURLException e)
    {
      return null;
    }
  }

  protected abstract URL getDataURL(String name, byte[] data) throws MalformedURLException;

  protected Enumeration findResources(String name)
  {
    URL url = this.findResource(name);

    if(url == null)
      return null;

    return Collections.enumeration(Collections.singleton(url));
  }

  public abstract boolean isStale();

  protected abstract byte[] getFile(String path);

  public static WebworkClassLoader getInstance(URL url)
  {
    return getInstance(url, ClassLoader.getSystemClassLoader());
  }

  public static WebworkClassLoader getInstance(URL url, ClassLoader parent)
  {
    WebworkClassLoader loader;
    File file = new File(url.getFile());
    if(file.isDirectory())
    {
      loader = new DirectoryClassLoader(file, parent);
    }
    else
    {
      loader = new JarClassLoader(file, parent);
    }
    return loader;
  }

  public abstract Object clone();
}