RabbitMQ初学之二:直接发送消息到队列

一. 背景

　　总前提：队列无论是在生产者声明还是在消费者声明，只有声明了，才能在RabbitMQ的管理界面看到该队列

　　生产者直接发送消息到队列，消费者直接消费队列中的消息，而不用指定exchange并绑定。这种需求下，分三种情况：① 生产者声明队列（指定队列名称），消费者不指定队列，而是直接消费生产者指定的队列；② 生产者声指定队列，但不声明队列，而是直接将消息发送到该队列，消费生声明该队列，并从该队列接收消息；③ 生产者声明队列并将消息发送到该队列，消费者也声明该队列，并从该队列消费消息，但是：生产者和消费者声明队列时指定的参数要一致，否则会报错。下面分别进行说明：

1. 生产者声明队列（指定队列名称），消费者不指定队列，而是直接消费生产者指定的队列，但是此时，声明队列的一方要先运行，否则消费者连不上队列，要报错

　　① 生产者代码

 import java.io.IOException;
 import com.rabbitmq.client.Channel;
 import com.rabbitmq.client.Connection;
 import com.rabbitmq.client.ConnectionFactory;

 public class Producer {
     private final static String QUEUE_NAME = "QUEUE1";  

     public static void main(String[] args) throws IOException {
         ConnectionFactory factory = new ConnectionFactory();
         factory.setHost("localhost");
         factory.setUsername("guest");
         factory.setPassword("guest");
         factory.setPort(5672);
         Connection connection = factory.newConnection();
         Channel channel = connection.createChannel();  

         // 声明队列
         channel.queueDeclare(QUEUE_NAME, true, false, false, null);
         String message = "Hello World!";  

         // 发行消息到队列
         channel.basicPublish("", QUEUE_NAME, null, message.getBytes());
         System.out.println(" [x] Sent '" + message + "'");  

         channel.close();
         connection.close();
     }
 }

　　2. 消费者

 import com.rabbitmq.client.ConnectionFactory;
 import com.rabbitmq.client.QueueingConsumer;
 import com.rabbitmq.client.Channel;
 import com.rabbitmq.client.Connection;  

 public class Reqv {

     private final static String QUEUE_NAME = "QUEUE1";  

     public static void main(String[] argv) throws Exception {  

         ConnectionFactory factory = new ConnectionFactory();
         factory.setUsername("guest");
         factory.setPassword("guest");
         factory.setHost("localhost");
         factory.setPort(5672);  

         Connection connection = factory.newConnection();
         Channel channel = connection.createChannel();  

         System.out.println(" [*] Waiting for messages. To exit press CTRL+C");

         QueueingConsumer consumer = new QueueingConsumer(channel);  

         // 消费者不声明队列，直接从队列中消费
         channel.basicConsume(QUEUE_NAME, true, consumer);
         while(true){
             QueueingConsumer.Delivery delivery = consumer.nextDelivery();
             String message = new String(delivery.getBody(),"UTF-8");
             System.out.println(" 【[x] Received 】：" + message);
         }
     }
 }

2.  生产者声指定队列，但不声明队列，而是直接将消息发送到该队列，消费生声明该队列，并从该队列接收消息，生产者可先运行）（不报错），但是发的消息无效（被丢弃），只有声明队列的一方运行后，在管理界面才能看到该队列

　　① 生产者

 import java.io.IOException;
 import com.rabbitmq.client.Channel;
 import com.rabbitmq.client.Connection;
 import com.rabbitmq.client.ConnectionFactory;

 public class Producer {
     private final static String QUEUE_NAME = "QUEUE2";  

     public static void main(String[] args) throws IOException {
         ConnectionFactory factory = new ConnectionFactory();
         factory.setHost("localhost");
         factory.setUsername("guest");
         factory.setPassword("guest");
         factory.setPort(5672);
         Connection connection = factory.newConnection();
         Channel channel = connection.createChannel();  

         String message = "Hello World!";  

         // 发行消息到队列
         channel.basicPublish("", QUEUE_NAME, null, message.getBytes());
         System.out.println(" [x] Sent '" + message + "'");  

         channel.close();
         connection.close();
     }
 }

　　② 消费者

 import com.rabbitmq.client.ConnectionFactory;
 import com.rabbitmq.client.QueueingConsumer;
 import com.rabbitmq.client.Channel;
 import com.rabbitmq.client.Connection;  

 public class Reqv {

     private final static String QUEUE_NAME = "QUEUE2";  

     public static void main(String[] argv) throws Exception {  

         ConnectionFactory factory = new ConnectionFactory();
         factory.setUsername("guest");
         factory.setPassword("guest");
         factory.setHost("localhost");
         factory.setPort(5672);  

         Connection connection = factory.newConnection();
         Channel channel = connection.createChannel();  

         // 声明队列
         channel.queueDeclare(QUEUE_NAME, true, false, false, null);
         System.out.println(" [*] Waiting for messages. To exit press CTRL+C");

         QueueingConsumer consumer = new QueueingConsumer(channel);  

         // 消费者不声明队列，直接从队列中消费
         channel.basicConsume(QUEUE_NAME, true, consumer);
         while(true){
             QueueingConsumer.Delivery delivery = consumer.nextDelivery();
             String message = new String(delivery.getBody(),"UTF-8");
             System.out.println(" 【[x] Received 】：" + message);
         }
     }
 }

3. 生产者声明队列并将消息发送到该队列，消费者也声明该队列，并从该队列消费消息，但是：生产者和消费者声明队列时指定的参数要一致，否则会报错。

　　① 生产者

 import java.io.IOException;
 import com.rabbitmq.client.Channel;
 import com.rabbitmq.client.Connection;
 import com.rabbitmq.client.ConnectionFactory;

 public class Producer {
     private final static String QUEUE_NAME = "QUEUE2";  

     public static void main(String[] args) throws IOException {
         ConnectionFactory factory = new ConnectionFactory();
         factory.setHost("localhost");
         factory.setUsername("guest");
         factory.setPassword("guest");
         factory.setPort(5672);
         Connection connection = factory.newConnection();
         Channel channel = connection.createChannel();  

         // 声明队列
         channel.queueDeclare(QUEUE_NAME, true, false, false, null);
         String message = "Hello World!";  

         // 发行消息到队列
         channel.basicPublish("", QUEUE_NAME, null, message.getBytes());
         System.out.println(" [x] Sent '" + message + "'");  

         channel.close();
         connection.close();
     }
 }

　　② 消费者

 import com.rabbitmq.client.ConnectionFactory;
 import com.rabbitmq.client.QueueingConsumer;
 import com.rabbitmq.client.Channel;
 import com.rabbitmq.client.Connection;  

 public class Reqv {

     private final static String QUEUE_NAME = "QUEUE2";  

     public static void main(String[] argv) throws Exception {  

         ConnectionFactory factory = new ConnectionFactory();
         factory.setUsername("guest");
         factory.setPassword("guest");
         factory.setHost("localhost");
         factory.setPort(5672);  

         Connection connection = factory.newConnection();
         Channel channel = connection.createChannel();  

         // 声明队列
         channel.queueDeclare(QUEUE_NAME, true, false, false, null);
         System.out.println(" [*] Waiting for messages. To exit press CTRL+C");

         QueueingConsumer consumer = new QueueingConsumer(channel);  

         // 消费者不声明队列，直接从队列中消费
         channel.basicConsume(QUEUE_NAME, true, consumer);
         while(true){
             QueueingConsumer.Delivery delivery = consumer.nextDelivery();
             String message = new String(delivery.getBody(),"UTF-8");
             System.out.println(" 【[x] Received 】：" + message);
         }
     }
 }