sessionserializer.java

低版本的tomcat 对于有些老版本的应用还真的需要老版的中间件

/*
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 * The Apache Software License, Version 1.1
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 * Copyright (c) 1999 The Apache Software Foundation.  All rights
 * reserved.
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 * modification, are permitted provided that the following conditions
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 *    any, must include the following acknowlegement:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowlegement may appear in the software itself,
 *    if and wherever such third-party acknowlegements normally appear.
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package org.apache.tomcat.session;

import java.io.*;
import java.util.*;
import javax.servlet.http.HttpSession;
import org.apache.tomcat.core.Request;

/**
	This class manages the serialization of HttpSession object across
	classloader reloads. It does this by first getting a copy of the 
	HttpSessions hashtable from the SessionManager and then using a
	special internal class ObjectInputStream that uses the newly created
	classloader to de-serialize the sessions. This class is called from
	within the ServletWrapper.handleReload() method. Much of this code
	is essentially the same as what I put into the Apache JServ release
	so it is pretty well tested. It also depends on having HttpSession
	implement the read/writeObject methods properly to only accept 
	objects that are serializable.

	@author <a href="mailto:[e-mail]">Jon S. Stevens</a>
*/
public final class SessionSerializer
{
	/**
		This is the method that does the serialization.
	*/
	public static final void doSerialization(Request req, ClassLoader cl, StandardManager sessionM) {
		// get the hashtable of sessions
		Hashtable sessions = sessionM.getSessions();
		
		try {
			// writes the session data out, but loses the contexts
			// because they cannot be serialized
			ByteArrayOutputStream b = new ByteArrayOutputStream();
			ObjectOutputStream o = new ObjectOutputStream(b);
			
			// write out the hashtable to the OOS
			o.writeObject(sessions);
			o.flush();
			
			// create the streams to read the sessions back in from.
			ByteArrayInputStream bIn = new ByteArrayInputStream (b.toByteArray());
			ObjectInputStream oOut= new ACLObjectInputStream(cl, bIn);
			
			// unserialize the sessions
			sessions = (Hashtable) oOut.readObject();

                        // put the new sessions into the manager
                        sessionM.setSessions(sessions);
                        
                        if (req.getSession(false) != null)
                        {
                            // replace the current session in the current request
                            HttpSession newSession = 
                                (HttpSession)sessions.get(req.getRequestedSessionId());
                            req.setSession(newSession);
                        }
			
		} catch (Exception e) {
		    // log the error. there shouldn't be one here though.
		    // XXX We should call Logger.log - this is a problem, but
		    // it's better to have a bug ( writing to out instead of log)
		    // than adding dependencies to context.
		    System.out.println( "SessionSerializer: " + e );
		}
	}
	
    /**
     * When deserializing the sessions during a class
     * loader reload, override the resolveClass() method 
     * so that it uses the AdaptiveClassLoader to deserialize
     * the sessions. This has the benefit of allowing 
     * objects that are only within the ACL's classpath 
     * to be found and deserialized.
     */
    private static final class ACLObjectInputStream extends ObjectInputStream {
	ClassLoader loader;
	
        ACLObjectInputStream(ClassLoader loader, InputStream bIn) throws IOException {
            super(bIn);
	    this.loader=loader;
        }
        protected Class resolveClass(ObjectStreamClass v)
            throws IOException, ClassNotFoundException {
			// use our new loader instead of the system loader
            return loader.loadClass(v.getName());
        }
    }
}