pluginsclassloader.java

模块化您的应用系统

package com.opensymphony.tonic.loaders.classloading;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import java.security.SecureClassLoader;
import java.util.HashMap;
import java.util.Map;
import java.util.Enumeration;
import java.util.Collections;
import java.net.URL;
import java.net.MalformedURLException;
import java.net.URLClassLoader;
import java.io.File;
import java.io.InputStream;
import java.io.IOException;

/**
 * @author Hani Suleiman ([e-mail])
 *         (derived from WebWork 1's WebworkClassLoader)
 */
public abstract class PluginsClassLoader extends SecureClassLoader implements Cloneable
{
    protected static Log log = LogFactory.getLog(PluginsClassLoader.class);

    protected String[] packages = null;
    private Map cache = new HashMap();

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

    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;

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

        if (url == null)
            return null;

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

    protected abstract byte[] getFile(String path);

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

    public static ClassLoader getInstance(URL url, ClassLoader parent)
    {
        ClassLoader loader;
        File file = new File(url.getFile());
        if (file.isDirectory())
        {
            log.warn("Making a DirectoryClassLoader for: " + file);
            loader = new URLClassLoader(new URL[]{url}, parent);
        }
        else
        {
            log.warn("Making a JarClassLoader for: " + file);
            loader = new JarClassLoader(file, parent);
        }
        return loader;
    }

    public abstract Object clone();

    /**
     * Method from WebWork1 webwork.util.ClassLoaderUtils
     */
    public static byte[] readStream(InputStream in, int size) throws IOException
    {
        if (in == null) return null;
        if (size == 0) return new byte[0];
        int currentTotal = 0;
        int bytesRead;
        byte[] data = new byte[size];
        while (currentTotal < data.length && (bytesRead = in.read(data, currentTotal, data.length - currentTotal)) >= 0)
            currentTotal += bytesRead;
        in.close();
        return data;
    }

    public URL getResource(String name)
    {
        URL url = findResource(name);

        if (name != null)
            return url;

        return super.getResource(name);
    }
}