com.feilong.lib.javassist.URLClassPath Maven / Gradle / Ivy

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feilong is a suite of core and expanded libraries that include utility classes, http, excel,cvs, io classes, and much much more.
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/*
 * Javassist, a Java-bytecode translator toolkit.
 * Copyright (C) 1999- Shigeru Chiba. All Rights Reserved.
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License.  Alternatively, the contents of this file may be used under
 * the terms of the GNU Lesser General Public License Version 2.1 or later,
 * or the Apache License Version 2.0.
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 */

package com.feilong.lib.javassist;

import java.io.IOException;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;

/**
 * A class search-path specified with URL (http).
 *
 * @see com.feilong.lib.javassist.ClassPath
 * @see ClassPool#insertClassPath(ClassPath)
 * @see ClassPool#appendClassPath(ClassPath)
 */
public class URLClassPath implements ClassPath{

    protected String hostname;

    protected int    port;

    protected String directory;

    protected String packageName;

    /**
     * Creates a search path specified with URL (http).
     *
     * 
     * This search path is used only if a requested
     * class name starts with the name specified by packageName.
     * If packageName is "org.javassist." and a requested class is
     * "org.javassist.test.Main", then the given URL is used for loading that class.
     * The URLClassPath obtains a class file from:
     *
     * 
     * http://www.javassist.org:80/java/classes/org/javassist/test/Main.class
     * 
     *
     * 
     * Here, we assume that host is "www.javassist.org",
     * port is 80, and directory is "/java/classes/".
     *
     * 
     * If packageName is null, the URL is used
     * for loading any class.
     *
     * @param host
     *            host name
     * @param port
     *            port number
     * @param directory
     *            directory name ending with "/".
     *            It can be "/" (root directory).
     *            It must start with "/".
     * @param packageName
     *            package name. It must end with "." (dot).
     */
    public URLClassPath(String host, int port, String directory, String packageName){
        hostname = host;
        this.port = port;
        this.directory = directory;
        this.packageName = packageName;
    }

    @Override
    public String toString(){
        return hostname + ":" + port + directory;
    }

    /**
     * Opens a class file with http.
     *
     * @return null if the class file could not be found.
     */
    @Override
    public InputStream openClassfile(String classname){
        try{
            URLConnection con = openClassfile0(classname);
            if (con != null){
                return con.getInputStream();
            }
        }catch (IOException e){}
        return null; // not found
    }

    private URLConnection openClassfile0(String classname) throws IOException{
        if (packageName == null || classname.startsWith(packageName)){
            String jarname = directory + classname.replace('.', '/') + ".class";
            return fetchClass0(hostname, port, jarname);
        }
        return null; // not found
    }

    /**
     * Returns the URL.
     *
     * @return null if the class file could not be obtained.
     */
    @Override
    public URL find(String classname){
        try{
            URLConnection con = openClassfile0(classname);
            InputStream is = con.getInputStream();
            if (is != null){
                is.close();
                return con.getURL();
            }
        }catch (IOException e){}
        return null;
    }

    /**
     * Reads a class file on an http server.
     *
     * @param host
     *            host name
     * @param port
     *            port number
     * @param directory
     *            directory name ending with "/".
     *            It can be "/" (root directory).
     *            It must start with "/".
     * @param classname
     *            fully-qualified class name
     */
    public static byte[] fetchClass(String host,int port,String directory,String classname) throws IOException{
        byte[] b;
        URLConnection con = fetchClass0(host, port, directory + classname.replace('.', '/') + ".class");
        int size = con.getContentLength();
        InputStream s = con.getInputStream();
        try{
            if (size <= 0){
                b = ClassPoolTail.readStream(s);
            }else{
                b = new byte[size];
                int len = 0;
                do{
                    int n = s.read(b, len, size - len);
                    if (n < 0){
                        throw new IOException("the stream was closed: " + classname);
                    }

                    len += n;
                }while (len < size);
            }
        }finally{
            s.close();
        }

        return b;
    }

    private static URLConnection fetchClass0(String host,int port,String filename) throws IOException{
        URL url;
        try{
            url = new URL("http", host, port, filename);
        }catch (MalformedURLException e){
            // should never reache here.
            throw new IOException("invalid URL?");
        }

        URLConnection con = url.openConnection();
        con.connect();
        return con;
    }
}