摘要: 本文讲述了JMS规范中五种消息类型，包括TextMessage、BytesMessage、MapMessage、StreamMessage和ObjectMessage
1.前言
ActiveMQ学习笔记(四)——通过ActiveMQ收发消息http://my.oschina.net/xiaoxishan/blog/380446 和ActiveMQ学习笔记(五)——使用Spring JMS收发消息http://my.oschina.net/xiaoxishan/blog/381209 中，发送和接受的消息类型都是TextMessage，即文本消息（如下面的代码所示）。显然消息类型只有文本类型是不能满足要求的。
//发送文本消息
session.createTextMessage(msg);
//接受文本消息
public void onMessage(Message msg) {
TextMessage message = (TextMessage) msg;
……
}
根据Message接口的方法，可以获取消息类型
String msgType = getJMSType()
根据 JSR 914: JavaTM Message Service (JMS) API ，JMS规范中的消息类型包括TextMessage、BytesMessage、MapMessage、StreamMessage和ObjectMessage等五种。ActiveMQ也有对应的实现，下面我们结合Spring JMS分别来看一下五种消息类型的收发代码。
2. 消息发送示例代码
/**
* 向默认队列发送text消息
*/
public void sendMessage(final String msg) {
String destination = jmsTemplate.getDefaultDestination().toString();
System.out.println("ProducerService向队列" + destination + "发送了消息：\t" + msg);
jmsTemplate.send(new MessageCreator() {
public Message createMessage(Session session) throws JMSException {
return session.createTextMessage(msg);
}
});
}
/**
* 向默认队列发送map消息
*/
public void sendMapMessage() {
jmsTemplate.send(new MessageCreator() {
public Message createMessage(Session session) throws JMSException {
MapMessage message = session.createMapMessage();
message.setString("name", "小西山");
return message;
}
});
}
/**
* 向默认队列发送Object消息
*/
public void sendObjectMessage() {
jmsTemplate.send(new MessageCreator() {
public Message createMessage(Session session) throws JMSException {
Staff staff = new Staff(1, "搬砖工"); // Staff必须实现序列化
ObjectMessage message = session.createObjectMessage(staff);
return message;
}
});
}
/**
* 向默认队列发送Bytes消息
*/
public void sendBytesMessage() {
jmsTemplate.send(new MessageCreator() {
public Message createMessage(Session session) throws JMSException {
String str = "BytesMessage 字节消息";
BytesMessage message = session.createBytesMessage();
message.writeBytes(str.getBytes());
return message;
}
});
}
/**
* 向默认队列发送Stream消息
*/
public void sendStreamMessage() {
jmsTemplate.send(new MessageCreator() {
public Message createMessage(Session session) throws JMSException {
String str = "StreamMessage 流消息";
StreamMessage message = session.createStreamMessage();
message.writeString(str);
message.writeInt(521);
return message;
}
});
}
3.消息接受示例代码
/**
* 接受消息
*/
public void receive(Destination destination) throws JMSException {
Message message = jmsTemplate.receive(destination);
// 如果是文本消息
if (message instanceof TextMessage) {
TextMessage tm = (TextMessage) message;
System.out.println("ConsumerService从队列" + destination.toString() + "收到了消息：\t" + tm.getText());
}
// 如果是Map消息
if (message instanceof MapMessage) {
MapMessage mm = (MapMessage) message;
System.out.println("ConsumerService从队列" + destination.toString() + "收到了消息：\t"
+ mm.getString("name"));
}
// 如果是Object消息
if (message instanceof ObjectMessage) {
ObjectMessage om = (ObjectMessage) message;
Staff staff = (Staff) om.getObject();
System.out.println("ConsumerService从队列" + destination.toString() + "收到了消息：\t" + staff);
}
// 如果是bytes消息
if (message instanceof BytesMessage) {
byte[] b = new byte[1024];
int len = -1;
BytesMessage bm = (BytesMessage) message;
while ((len = bm.readBytes(b)) != -1) {
System.out.println(new String(b, 0, len));
}
}
// 如果是Stream消息
if (message instanceof StreamMessage) {
StreamMessage sm = (StreamMessage) message;
System.out.println(sm.readString());
System.out.println(sm.readInt());
}
}