ActiveMQ之三 -- 使用ActiveMQ来传送文件

这个方法还有待研究，目前还有如下几个疑点：
1. ActiveMQ 报出这样的信息：

INFO | Usage Manager memory limit ( 1048576 ) reached for topic://EXCHANGE.FILE. Producers will be throttled to the rate at which messages are removed from this
destination to prevent flooding it. See http://activemq.apache.org/producer-flow-control.html for more info

2. 这种以异步方式传送资料，能保证客户端能以正确的顺序接收到文件段麽？

使用ActiveMQ传送文件，发送端必须将文件拆成一段一段，每段封装在独立的Message中，逐次发送到客户端。例如下面的例子，Producer通过发送命令，告诉文件传送的开始，发送中，结束。客户端接收到这些命令之后，就知道如何接收资料了。

客户端收到内容后，根据命令将内容合并到一个文件中。 

package  org.apache.activemq.exchange.file;

import  java.io.BufferedOutputStream;
import  java.io.FileOutputStream;
import  java.io.IOException;

import  javax.jms.Connection;
import  javax.jms.ConnectionFactory;
import  javax.jms.Destination;
import  javax.jms.JMSException;
import  javax.jms.Message;
import  javax.jms.MessageConsumer;
import  javax.jms.Session;
import  javax.jms.StreamMessage;

import  org.apache.activemq.ActiveMQConnectionFactory;

public   class  Consumer {

     /**
     *  @param  args
      */
     public   static   void  main(String[] args)  throws  JMSException, IOException {
        ConnectionFactory factory  =   new  ActiveMQConnectionFactory( " tcp://localhost:61616 " );

        Connection connection  =  factory.createConnection();
        connection.start();

        Session session  =  connection.createSession( false , Session.AUTO_ACKNOWLEDGE);

        Destination destination  =  session.createTopic( " EXCHANGE.FILE " );

        MessageConsumer consumer  =  session.createConsumer(destination);

         boolean  appended  =   false ;
         try  {
             while  ( true ) {
                Message message  =  consumer.receive( 5000 );
                 if  (message  ==   null ) {
                     continue ;
                }

                 if  (message  instanceof  StreamMessage) {
                    StreamMessage streamMessage  =  (StreamMessage) message;
                    String command  =  streamMessage.getStringProperty( " COMMAND " );
                    
                     if  ( " start " .equals(command)) {
                        appended  =   false ;
                         continue ;
                    }

                     if  ( " sending " .equals(command)) {
                         byte [] content  =   new   byte [ 4096 ];
                        String file_name  =  message.getStringProperty( " FILE_NAME " );
                        BufferedOutputStream bos  =   null ;
                        bos  =   new  BufferedOutputStream( new  FileOutputStream( " c:/ "   +  file_name, appended));
                         if  ( ! appended) {
                            appended  =   true ;
                        }
                         while  (streamMessage.readBytes(content)  >   0 ) {
                            bos.write(content);
                        }
                        bos.close();
                         continue ;
                    }

                     if  ( " end " .equals(command)) {
                        appended  =   false ;
                         continue ;
                    }
                }
            }
        }  catch  (JMSException e) {
             throw  e;
        }  finally  {
             if  (connection  !=   null ) {
                connection.close();
            }
        }

    }

}

发送端将文件分包，逐次发送到客户端 

package  org.apache.activemq.exchange.file;

import  java.io.BufferedInputStream;
import  java.io.IOException;
import  java.io.InputStream;

import  javax.jms.Connection;
import  javax.jms.ConnectionFactory;
import  javax.jms.Destination;
import  javax.jms.JMSException;
import  javax.jms.MessageProducer;
import  javax.jms.Session;
import  javax.jms.StreamMessage;

import  org.apache.activemq.ActiveMQConnectionFactory;

public   class  Publisher {

     public   static  String FILE_NAME  =   " 01.mp3 " ;
    
     public   static   void  main(String[] args)  throws  JMSException, IOException {
        ConnectionFactory factory  =   new  ActiveMQConnectionFactory( " tcp://localhost:61616 " );
        Connection connection  =  factory.createConnection();
        connection.start();
        Session session  =  connection.createSession( false , Session.AUTO_ACKNOWLEDGE);
        Destination destination  =  session.createTopic( " EXCHANGE.FILE " );        
        MessageProducer producer  =  session.createProducer(destination);
         long  time  =  System.currentTimeMillis();
        
         // 通知客户端开始接受文件
        StreamMessage message  =  session.createStreamMessage();
        message.setStringProperty( " COMMAND " ,  " start " );
        producer.send(message);
        
         // 开始发送文件
         byte [] content  =   new   byte [ 4096 ];
        InputStream ins  =  Publisher. class .getResourceAsStream(FILE_NAME);
        BufferedInputStream bins  =   new  BufferedInputStream(ins);
         while  (bins.read(content)  >   0 ) {
             //
            message  =  session.createStreamMessage();
            message.setStringProperty( " FILE_NAME " , FILE_NAME);
            message.setStringProperty( " COMMAND " ,  " sending " );
            message.clearBody();
            message.writeBytes(content);
            producer.send(message);
        }
        bins.close();
        ins.close();
        
         // 通知客户端发送完毕
        message  =  session.createStreamMessage();
        message.setStringProperty( " COMMAND " ,  " end " );
        producer.send(message);
        
        connection.close();
        
        System.out.println( " Total Time costed :  "   +  (System.currentTimeMillis()  -  time)  +   "  mili seconds " );
    }
}