非常感谢http://wubin850219.iteye.com/blog/1003840
在前面的已经提到了一对一的情况;现在一个生产者与多个消费者的情况（Work Queues）。Work Queues的示意图如下：
对于上图的模型中对于c端的worker来说。RabbitMQ服务器可能一直发送多个消息给一个worker，而另一个可能几乎不做任何事情。这样就会导致一个worker很忙，而另一个却很空闲。这种情况可能都不想出现。如何解决这个问题呢。当然最理想的情况是均匀分配消息给每个worker。我们可能通过channel . basicQos(1)方法（PRefetchCount = 1 ）来设置同一时间每次发给一个消息给一个worker。示意图如下：
P端的程序如下：
java代码
package com.abin.rabbitmq; import com.rabbitmq.client.Channel; import com.rabbitmq.client.Connection; import com.rabbitmq.client.ConnectionFactory; import com.rabbitmq.client.MessageProperties; public class NewTask { private static final String TASK_QUEUE_NAME = "task_queue"; public static void main(String[] argv) throws Exception { ConnectionFactory factory = new ConnectionFactory(); factory.setHost("localhost"); Connection connection = factory.newConnection(); Channel channel = connection.createChannel(); //声明此队列并且持久化 channel.queueDeclare(TASK_QUEUE_NAME, true, false, false, null); String message = getMessage(argv); channel.basicPublish("", TASK_QUEUE_NAME, MessageProperties.PERSISTENT_TEXT_PLAIN, message.getBytes());//持久化消息 System.out.println(" [x] Sent '" + message + "'"); channel.close(); connection.close(); } private static String getMessage(String[] strings) { if (strings.length < 1) return "Hello World!"; return joinStrings(strings, " "); } private static String joinStrings(String[] strings, String delimiter) { int length = strings.length; if (length == 0) return ""; StringBuilder Words = new StringBuilder(strings[0]); for (int i = 1; i < length; i++) { words.append(delimiter).append(strings[i]); } return words.toString(); } } 多次运行此程序并传入的参数分别为“First message ”，“Secondmessage ”，“Third message ”，“Fourth message ”，“Fifth message ”
C端的程序如下：
Java代码package com.abin.rabbitmq; import com.rabbitmq.client.Channel; import com.rabbitmq.client.Connection; import com.rabbitmq.client.ConnectionFactory; import com.rabbitmq.client.QueueingConsumer; public class Worker { private static final String TASK_QUEUE_NAME = "task_queue"; public static void main(String[] argv) throws Exception { ConnectionFactory factory = new ConnectionFactory(); factory.setHost("localhost"); Connection connection = factory.newConnection(); Channel channel = connection.createChannel(); //声明此队列并且持久化 channel.queueDeclare(TASK_QUEUE_NAME, true, false, false, null); System.out.println(" [*] Waiting for messages. To exit press CTRL+C"); channel.basicQos(1);//告诉RabbitMQ同一时间给一个消息给消费者 /* We're about to tell the server to deliver us the messages from the queue. * Since it will push us messages asynchronously, * we provide a callback in the form of an object that will buffer the messages * until we're ready to use them. That is what QueueingConsumer does.*/ QueueingConsumer consumer = new QueueingConsumer(channel); /* 把名字为TASK_QUEUE_NAME的Channel的值回调给QueueingConsumer,即使一个worker在处理消息的过程中停止了，这个消息也不会失效 */ channel.basicConsume(TASK_QUEUE_NAME, false, consumer); while (true) { QueueingConsumer.Delivery delivery = consumer.nextDelivery();//得到消息传输信息 String message = new String(delivery.getBody()); System.out.println(" [x] Received '" + message + "'"); doWork(message); System.out.println(" [x] Done"); channel.basicAck(delivery.getEnvelope().getDeliveryTag(), false);//下一个消息 } } private static void doWork(String task) throws InterruptedException { for (char ch : task.toCharArray()) { if (ch == '.') Thread.sleep(1000);//这里是假装我们很忙 } } } 开启两个worker分别运行。运行结果如：
c1的结果：
Java代码[*] Waiting for messages. To exit press CTRL+C [x] Received 'First message' [x] Received 'Third message' [x] Received 'Fifth message' c2的结果
Java代码[*] Waiting for messages. To exit press CTRL+C [x] Received 'Second message' [x] Received 'Fourth message'
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