NIO を使用している場合は、フレームワークを使用することもお勧めします。私はApache Minaを使用してきましたが、これをお勧めします。
ブロッキング IO に関しては、基本的に、着信接続を受け入れ、各接続を処理する追加のスレッドを生成するリスナー スレッドが必要になります。以下は、もともと Apache Felix プロジェクトに提供されたリスナー コードの例です。完全であるが変更されたバージョンを探している場合は、ここでソースを参照できます。
例えば
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.felix.shell.remote;
import java.io.IOException;
import java.io.PrintStream;
import java.net.ServerSocket;
import java.net.Socket;
import java.net.SocketException;
/**
* Implements a simple listener that will accept a single connection.
* <p/>
*
* @author Dieter Wimberger (wimpi)
*/
class Listener
{
private int m_Port;
private Thread m_ListenerThread;
private boolean m_Stop = false;
private ServerSocket m_ServerSocket;
private AtomicInteger m_UseCounter;
private int m_MaxConnections;
/**
* Activates this listener on a listener thread (telnetconsole.Listener).
*/
public void activate()
{
//configure from system property
try
{
m_Port = Integer.parseInt( System.getProperty( "osgi.shell.telnet.port", "6666" ) );
}
catch ( NumberFormatException ex )
{
Activator.getServices().error( "Listener::activate()", ex );
}
try
{
m_MaxConnections = Integer.parseInt( System.getProperty( "osgi.shell.telnet.maxconn", "2" ) );
}
catch ( NumberFormatException ex )
{
Activator.getServices().error( "Listener::activate()", ex );
}
m_UseCounter = new AtomicInteger( 0 );
m_ListenerThread = new Thread( new Acceptor(), "telnetconsole.Listener" );
m_ListenerThread.start();
}//activate
/**
* Deactivates this listener.
* <p/>
* The listener's socket will be closed, which should cause an interrupt in the
* listener thread and allow for it to return. The calling thread joins the listener
* thread until it returns (to ensure a clean stop).
*/
public void deactivate()
{
try
{
m_Stop = true;
//wait for the listener thread
m_ServerSocket.close();
m_ListenerThread.join();
}
catch ( Exception ex )
{
Activator.getServices().error( "Listener::deactivate()", ex );
}
}//deactivate
/**
* Class that implements the listener's accept logic as a <tt>Runnable</tt>.
*/
private class Acceptor implements Runnable
{
/**
* Listens constantly to a server socket and handles incoming connections.
* One connection will be accepted and routed into the shell, all others will
* be notified and closed.
* <p/>
* The mechanism that should allow the thread to unblock from the ServerSocket.accept() call
* is currently closing the ServerSocket from another thread. When the stop flag is set,
* this should cause the thread to return and stop.
*/
public void run()
{
try
{
/*
A server socket is opened with a connectivity queue of a size specified
in int floodProtection. Concurrent login handling under normal circumstances
should be handled properly, but denial of service attacks via massive parallel
program logins should be prevented with this.
*/
m_ServerSocket = new ServerSocket( m_Port, 1 );
do
{
try
{
Socket s = m_ServerSocket.accept();
if ( m_UseCounter.get() >= m_MaxConnections )
{
//reject with message
PrintStream out = new PrintStream( s.getOutputStream() );
out.print( INUSE_MESSAGE );
out.flush();
//close
out.close();
s.close();
}
else
{
m_UseCounter.increment();
//run on the connection thread
Thread connectionThread = new Thread( new Shell( s, m_UseCounter ) );
connectionThread.start();
}
}
catch ( SocketException ex )
{
}
}
while ( !m_Stop );
}
catch ( IOException e )
{
Activator.getServices().error( "Listener.Acceptor::activate()", e );
}
}//run
}//inner class Acceptor
private static final String INUSE_MESSAGE = "Connection refused.\r\n"
+ "All possible connections are currently being used.\r\n";
}//class Listener
他の例は、こことここにあります。
負荷が増えると、ブロッキング モデルに対する NIO の利点が発揮されることに注意してください。ある時点から、スレッドの作成、管理、およびコンテキストの切り替えのための余分な作業量によって、システムのパフォーマンスが制限されます。