ActiveMQ之三 -- 使用ActiveMQ來傳送文件

這個方法還有待研究，目前還有如下幾個疑點：
1. ActiveMQ 報出這樣的信息：

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. 這種以異步方式傳送資料，能保證客戶端能以正確的順序接收到文件段麼？

 

使用ActiveMQ傳送文件，發送端必須將文件拆成一段一段，每段封裝在獨立的Message中，逐次發送到客戶端。例如下面的例子，Producer通過發送命令，告訴文件傳送的開始，發送中，結束。客戶端接收到這些命令之後，就知道如何接收資料了。

客戶端收到內容後，根據命令將內容合併到一個文件中。  

 

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();
            }
        }

    }

}

 

發送端將文件分包，逐次發送到客戶端  

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();
        
        //通知客戶端開始接受文件
        StreamMessage message = session.createStreamMessage();
        message.setStringProperty("COMMAND", "start");
        producer.send(message);
        
        //開始發送文件
        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();
        
        //通知客戶端發送完畢
        message = session.createStreamMessage();
        message.setStringProperty("COMMAND", "end");
        producer.send(message);
        
        connection.close();
        
        System.out.println("Total Time costed : " + (System.currentTimeMillis() - time) + " mili seconds");
    }
}