deadlockprintstream.java

java程序写系统的服务

package org.tanukisoftware.wrapper.test;

/*
 * Copyright (c) 1999, 2006 Tanuki Software Inc.
 * 
 * Permission is hereby granted, free of charge, to any person
 * obtaining a copy of the Java Service Wrapper and associated
 * documentation files (the "Software"), to deal in the Software
 * without  restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sub-license,
 * and/or sell copies of the Software, and to permit persons to
 * whom the Software is furnished to do so, subject to the
 * following conditions:
 * 
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES 
 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 
 * NON-INFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT 
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, 
 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING 
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 */

// $Log: DeadlockPrintStream.java,v $
// Revision 1.4  2006/02/24 05:45:58  mortenson
// Update the copyright.
//
// Revision 1.3  2005/05/23 02:39:30  mortenson
// Update the copyright information.
//
// Revision 1.2  2004/01/16 04:41:55  mortenson
// The license was revised for this version to include a copyright omission.
// This change is to be retroactively applied to all versions of the Java
// Service Wrapper starting with version 3.0.0.
//
// Revision 1.1  2003/10/18 07:35:30  mortenson
// Add test cases to test how the wrapper handles it when the System.out stream
// becomes deadlocked.  This can happen if buggy usercode overrides those streams.
//

import java.io.IOException;
import java.io.PrintStream;

/**
 * A print stream which can be put into a state in which all calls to write
 *  to it will result in the calling threads deadlocking in the call.
 * Obviously, this class will not be useful to many as it is for tests.
 *
 * @author Leif Mortenson <[e-mail]>
 * @version $Revision: 1.4 $
 */
public class DeadlockPrintStream extends PrintStream {
    /** The Wrapped PrintStream. */
    private PrintStream m_out;
    
    /** True if calling threads should be deadlocked. */
    private boolean m_deadlock;
    
    /*---------------------------------------------------------------
     * Constructors
     *-------------------------------------------------------------*/
    /**
     * Creates a new DeadlockPrintStream wrapped around another PrintStream.
     *
     * @param out The PrintStream which will be wrapped by this new stream.
     */
    public DeadlockPrintStream( PrintStream out )
    {
        super( out );
        
        m_out = out;
    }
    
    /*---------------------------------------------------------------
     * PrintStream Methods
     *-------------------------------------------------------------*/
    public void write( int b )
    {
        deadlock();
        m_out.write( b );
    }
    
    public void write( byte[] b )
        throws IOException
    {
        deadlock();
        m_out.write( b );
    }
    
    public void write( byte[] b, int off, int len )
    {
        deadlock();
        m_out.write( b, off, len );
    }
    
    public void flush()
    {
        deadlock();
        m_out.flush();
    }
    
    public void close()
    {
        deadlock();
        m_out.close();
    }
    
    /*---------------------------------------------------------------
     * Methods
     *-------------------------------------------------------------*/
    /**
     * This call will not return as long as the m_deadLock flag is set.
     *  If it is ever cleared with a call to setDeadlock(), stuck threads
     *  will all be released.
     */
    private void deadlock()
    {
        if ( m_deadlock )
        {
            synchronized( this )
            {
                while( m_deadlock )
                {
                    try
                    {
                        this.wait();
                    }
                    catch ( InterruptedException e )
                    {
                        // Ignore
                    }
                }
            }
        }
    }
    
    /**
     * Sets or clears the deadlock flag.  If set, calls to any other method
     *  of this class will result in the calling thread being deadlocked.
     *  They will be released if the flag is cleared with this method.
     *
     * @param deadlock True to set the flag, false to clear it.
     */
    public void setDeadlock( boolean deadlock )
    {
        m_deadlock = deadlock;
        if ( !m_deadlock )
        {
            synchronized( this )
            {
                // Release any threads that are waiting.
                this.notifyAll();
            }
        }
    }
}