activemq中的selector

深藏阁楼爱情的钟 2022-03-30 08:38 449阅读 0赞

### activemq中的selector ###

*  Producer.java
 *  Consumer.java

> activemq消息中间件可以过滤消息，也就是selector，selector遵循sql 92语法。可以使用IN、NOT IN、LIKE等，例如： LIKE ‘12%3’ （‘123’ true，‘12993’ true，‘1234’ false） LIKE ‘l\_se’ （‘lose’ true，‘loose’ false） LIKE ‘\_%’ ESCAPE ‘’ （’\_foo’ true，‘foo’ false）。

> selector只会过滤property中的属性，但是这些属性在消费的时候并没有值，是null。

# Producer.java #

public class Producer {
        //用户名
        private static final String USERNAME = ActiveMQConnection.DEFAULT_USER;
        //密码
        private static final String PASSWORD = ActiveMQConnection.DEFAULT_PASSWORD;
        //url
        private static final String URL = ActiveMQConnection.DEFAULT_BROKER_URL;
    
    
        private static Connection connection = null;
        private static Session session = null;
    
        public static void main(String[] args) throws JMSException {
            ActiveMQConnectionFactory factory = new ActiveMQConnectionFactory(USERNAME,PASSWORD,URL);
            connection = factory.createConnection();
            connection.start();
            session = connection.createSession(false,Session.CLIENT_ACKNOWLEDGE);
    
            Queue selector1 = session.createQueue("selector1");
            MessageProducer producer = session.createProducer(selector1);
    
            MapMessage message1 = session.createMapMessage();
            message1.setString("name","张1");
            message1.setIntProperty("age",23);//selector只能过滤property中的字段，但是这些字段消费的时候是没有的
            message1.setStringProperty("gender","男");
            MapMessage message2 = session.createMapMessage();
            message2.setString("name","张2");
            message2.setIntProperty("age",33);
            message2.setStringProperty("gender","女");
            MapMessage message3 = session.createMapMessage();
            message3.setString("name","张3");
            message3.setIntProperty("age",43);
            message3.setStringProperty("gender","男");
            MapMessage message4 = session.createMapMessage();
            message4.setString("name","张4");
            message4.setIntProperty("age",53);
            message4.setStringProperty("gender","女");
    
            producer.send(message1);
            producer.send(message2);
            producer.send(message3);
            producer.send(message4);
    
            connection.close();
    
        }

# Consumer.java #

public class Consumer {
        //用户名
        private static final String USERNAME = ActiveMQConnection.DEFAULT_USER;
        //密码
        private static final String PASSWORD = ActiveMQConnection.DEFAULT_PASSWORD;
        //url
        private static final String URL = ActiveMQConnection.DEFAULT_BROKER_URL;
    
        private static String SELECTOR_MAN = "gender = '男'";
        private static String SELECTOR_AGE = "age > 30";
    
        private static String SELECTOR_MAN_AGE = "age > 30 and gender = '男'";
    
        private static Connection connection = null;
        private static Session session = null;
    
        public static void main(String[] args) throws Exception {
            ActiveMQConnectionFactory factory = new ActiveMQConnectionFactory(USERNAME,PASSWORD,URL);
            connection = factory.createConnection();
            connection.start();
            session = connection.createSession(false,Session.CLIENT_ACKNOWLEDGE);
    
            Queue selector1 = session.createQueue("selector1");
            MessageConsumer consumer = session.createConsumer(selector1,SELECTOR_MAN_AGE);
    
            consumer.setMessageListener(new MessageListener() {
                @Override
                public void onMessage(Message message) {
                    System.out.println("收到消息");
                    if(message instanceof MapMessage){
                        MapMessage m = (MapMessage) message;
                        System.out.println(m.toString());
                        try {
                            System.out.println(m.getString("name"));
                            //System.out.println(m.getString("age"));
                            //System.out.println(m.getString("gender"));
                            m.acknowledge();
                        } catch (JMSException e) {
                            e.printStackTrace();
                        }
                    }
    
                }
            });
    
        }
    }

注意

> Selectors表达式中的日期和时间需要使用标准的long型毫秒值，表达式中的属性不会自动进行类型转换

message1.seStringProperty("age","23“)
    "age > 1" 求值结果是false。