MINA v2.0 快速开始指南

 

介绍

这个指南过程将带你建立一个MINA时间服务程序.  以下要事先准备。

  • MINA 2.x Core
  • JDK 1.5 or greater
  • SLF4J 1.3.0 or greater
    • Log4J 1.2 users: slf4j-api.jar, slf4j-log4j12.jar, and Log4J 1.2.x
    • Log4J 1.3 users: slf4j-api.jar, slf4j-log4j13.jar, and Log4J 1.3.x
    • java.util.logging users: slf4j-api.jar and slf4j-jdk14.jar
    • IMPORTANT: Please make sure you are using the right slf4j-*.jar that matches to your logging framework.
      For instance, slf4j-log4j12.jar and log4j-1.3.x.jar can not be used together, and will malfunction.

我已经在Windows© 2000 professional 和 linux下测试过.  如果你发现这个程序有任何问题, 请不要犹豫联系我们并告知MINA开发者.  并且这个指南和平台无关(IDE, editors..etc). 这个指南可以在你任何你认为适合的环境编译.  为简要起见去除了编辑和执行过程. 如果你需要学习如何编译或者执行java程序，请参考Java tutorial.

Writing the MINA time server 

我们将重创建一个叫MinaTimeServer.java的文件开始，代码如下：:

public class MinaTimeServer {

    public static void main(String[] args) {
    	// code will go here next
    }
}

这段代码将直接对所有.  我们简单定一个main 方法 去启动程序.  并在这时, 我们将开始增加代码组成我们的服务.  首先, 我们需要一个监听传入连接的对象.  应为这个程序是基于TCP/IP ,所以我们将在程序中增加一个SocketAcceptor（Socket适配器） .

import org.apache.mina.core.service.IoAcceptor;
import org.apache.mina.transport.socket.nio.NioSocketAcceptor;

public class MinaTimeServer
{

    public static void main( String[] args )
    {
        IoAcceptor acceptor = new NioSocketAcceptor();
    }

}

这里我们通过NioSocketAcceptor类继续定义handler 类并且把NioSocketAcceptor类和端口绑定上.

下面我们对配置增加一个过滤器. 这个过滤器将记录所有信息比如创建sessions, messages received, messages sent, session closed. 下面的过滤器是一个ProtocolCodecFilter. 此过滤器将转化二进制或具体数据协议转化为信息对象，反之亦然. 我们用一个现有的TextLine 工厂应为他会为你处理文本基础信息(你不需要写为它写编解码器的一部分)

 

import java.nio.charset.Charset;

import org.apache.mina.core.service.IoAcceptor;
import org.apache.mina.filter.codec.ProtocolCodecFilter;
import org.apache.mina.filter.codec.textline.TextLineCodecFactory;
import org.apache.mina.filter.logging.LoggingFilter;
import org.apache.mina.transport.socket.nio.NioSocketAcceptor;

public class MinaTimeServer
{
    public static void main( String[] args )
    {
        IoAcceptor acceptor = new NioSocketAcceptor();

        acceptor.getFilterChain().addLast( "logger", new LoggingFilter() );
        acceptor.getFilterChain().addLast( "codec", new ProtocolCodecFilter( new TextLineCodecFactory( Charset.forName( "UTF-8" ))));
    }
}

 

在这一点上，我们将确定处理类，将用于服务客户端连接，并请求求当前时间. 这个类必须实现IoHandler接口. 我们所有的程序使用MINA, this becomes the workhorse of the program, as it services all incoming requests from the clients. For this tutorial, we will extend the class IoHandlerAdapter. This is a class that follows the adapter design pattern which simplifies the amount of code that needs to be written in order to satisfy the requirement of passing in a class that implements the IoHandler interface.
import java.io.IOException;
import java.nio.charset.Charset;

import org.apache.mina.core.service.IoAcceptor;
import org.apache.mina.filter.codec.ProtocolCodecFilter;
import org.apache.mina.filter.codec.textline.TextLineCodecFactory;
import org.apache.mina.filter.logging.LoggingFilter;
import org.apache.mina.transport.socket.nio.NioSocketAcceptor;

public class MinaTimeServer
{
    public static void main( String[] args ) throws IOException
    {
        IoAcceptor acceptor = new NioSocketAcceptor();

        acceptor.getFilterChain().addLast( "logger", new LoggingFilter() );
        acceptor.getFilterChain().addLast( "codec", new ProtocolCodecFilter( new TextLineCodecFactory( Charset.forName( "UTF-8" ))));

        acceptor.setHandler(  new TimeServerHandler() );
    }
}

We will now add in the NioSocketAcceptor configuration. This will allow us to make socket-specific settings for the socket that will be used to accept connections from clients.

import java.io.IOException;
import java.nio.charset.Charset;

import org.apache.mina.core.session.IdleStatus;
import org.apache.mina.core.service.IoAcceptor;
import org.apache.mina.filter.codec.ProtocolCodecFilter;
import org.apache.mina.filter.codec.textline.TextLineCodecFactory;
import org.apache.mina.filter.logging.LoggingFilter;
import org.apache.mina.transport.socket.nio.NioSocketAcceptor;

public class MinaTimeServer
{
    public static void main( String[] args ) throws IOException
    {
        IoAcceptor acceptor = new NioSocketAcceptor();

        acceptor.getFilterChain().addLast( "logger", new LoggingFilter() );
        acceptor.getFilterChain().addLast( "codec", new ProtocolCodecFilter( new TextLineCodecFactory( Charset.forName( "UTF-8" ))));

        acceptor.setHandler(  new TimeServerHandler() );

        acceptor.getSessionConfig().setReadBufferSize( 2048 );
        acceptor.getSessionConfig().setIdleTime( IdleStatus.BOTH_IDLE, 10 );
    }
}

There are 2 new lines in the MinaTimeServer class. These methods set the set the IoHandler, input buffer size and the idle property for the sessions. The buffer size will be specified in order to tell the underlying operating system how much room to allocate for incoming data. The second line will specify when to check for idle sessions. In the call to setIdleTime, the first parameter defines what actions to check for when determining if a session is idle, the second parameter defines the length of time in seconds that must occur before a session is deemed to be idle.

The code for the handler is shown below:

import java.util.Date;

import org.apache.mina.core.session.IdleStatus;
import org.apache.mina.core.service.IoHandlerAdapter;
import org.apache.mina.core.session.IoSession;

public class TimeServerHandler extends IoHandlerAdapter
{
    @Override
    public void exceptionCaught( IoSession session, Throwable cause ) throws Exception
    {
        cause.printStackTrace();
    }

    @Override
    public void messageReceived( IoSession session, Object message ) throws Exception
    {
        String str = message.toString();
        if( str.trim().equalsIgnoreCase("quit") ) {
            session.close();
            return;
        }

        Date date = new Date();
        session.write( date.toString() );
        System.out.println("Message written...");
    }

    @Override
    public void sessionIdle( IoSession session, IdleStatus status ) throws Exception
    {
        System.out.println( "IDLE " + session.getIdleCount( status ));
    }
}

The methods used in this class are exceptionCaught, messageReceived and sessionIdle. exceptionCaught should always be defined in a handler to process and exceptions that are raised in the normal course of handling remote connections. If this method is not defined, exceptions may not get properly reported.

The exceptionCaught method will simply print the stack trace of the error and close the session. For most programs, this will be standard practice unless the handler can recover from the exception condition.

The messageReceived method will receive the data from the client and write back to the client the current time. If the message received from the client is the word "quit", then the session will be closed. This method will also print out the current time to the client. Depending on the protocol codec that you use, the object (second parameter) that gets passed in to this method will be different, as well as the object that you pass in to the session.write(Object) method. If you do not specify a protocol codec, you will most likely receive a IoBuffer object, and be required to write out a IoBuffer object.

The sessionIdle method will be called once a session has remained idle for the amount of time specified in the call acceptor.getSessionConfig().setIdleTime( IdleStatus.BOTH_IDLE, 10 );.

All that is left to do is define the socket address that the server will listen on, and actually make the call that will start the server. That code is shown below:

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.charset.Charset;

import org.apache.mina.core.service.IoAcceptor;
import org.apache.mina.core.session.IdleStatus;
import org.apache.mina.filter.codec.ProtocolCodecFilter;
import org.apache.mina.filter.codec.textline.TextLineCodecFactory;
import org.apache.mina.filter.logging.LoggingFilter;
import org.apache.mina.transport.socket.nio.NioSocketAcceptor;

public class MinaTimeServer
{
    private static final int PORT = 9123;

    public static void main( String[] args ) throws IOException
    {
        IoAcceptor acceptor = new NioSocketAcceptor();

        acceptor.getFilterChain().addLast( "logger", new LoggingFilter() );
        acceptor.getFilterChain().addLast( "codec", new ProtocolCodecFilter( new TextLineCodecFactory( Charset.forName( "UTF-8" ))));

        acceptor.setHandler( new TimeServerHandler() );
	acceptor.getSessionConfig().setReadBufferSize( 2048 );
        acceptor.getSessionConfig().setIdleTime( IdleStatus.BOTH_IDLE, 10 );
        acceptor.bind( new InetSocketAddress(PORT) );
    }
}

As you see, there is a call to acceptor.setLocalAddress( new InetSocketAddress(PORT) );. This method defines what host and port this server will listen on. The final method is a call to IoAcceptor.bind(). This method will bind to the specified port and start processing of remote clients.

Try out the Time server 

At this point, we can go ahead and compile the program.  Once you have compiled the program you can run the program in order to test out what happens.  The easiest way to test the program is to start the program, and then telnet in to the program:

Client Output
Server Output
user@myhost:~> telnet 127.0.0.1 9123
Trying 127.0.0.1...
Connected to 127.0.0.1.
Escape character is '^]'.
hello
Wed Oct 17 23:23:36 EDT 2007
quit
Connection closed by foreign host.
user@myhost:~> 		MINA Time server started.
Message written...

What's Next?

Please visit our Documentation page to find out more resources. You can also keep reading other tutorials.

posted on 2009-06-10 09:43  zcz  阅读(1459)  评论(0)    收藏  举报

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