应用场景：用户下单未支付，需要系统自动取消订单
解决方案：
1，实现定时器轮询订单，将未支付满30分钟后的订单，进行更新状态，变为取消订单
2，用户查看订单时，先将之前未支付的订单进行更新为取消订单
3，延时队列实现取消订单
ps:还有其它方案，一时想不起来了

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优缺点：
方案一：
优点：实现简单
缺点：轮询太消耗资源了，数据库说- -噢顶木住啦
方案二：
优点：实现简了，如果不需要下单减库存或者锁库存操作，该方案实用。
缺点：下单时已经锁定了库存，简单说，如果不取消订单，库存就一直被锁。老板说》你走人吧
方案三：
优点：好用！！！！

代码实现：

连接类：

public class RabbitmqConfiguration {private final String SERVER_HOST="127.0.0.1";//rabbitmq 服务器地址private final int PORT=5672;//端口号private final String USER_NAME="guest";//用户名private final String PASSWORD="guest";//密码private final boolean QUEUE_SAVE =true;//队列是否持久化private final String MESSAGE_SAVE = "1" ;//消息持久化  1，0//rabbitmq 连接工厂private final ConnectionFactory RAB_FACTORY = new ConnectionFactory();private Connection connection;public void init() throws Exception{RAB_FACTORY.setHost(SERVER_HOST);RAB_FACTORY.setPort(PORT);RAB_FACTORY.setUsername(USER_NAME);RAB_FACTORY.setPassword(PASSWORD);RAB_FACTORY.setVirtualHost("/");this.connection = RAB_FACTORY.newConnection();}public Connection getConnection() {return connection;}public void setConnection(Connection connection) {this.connection = connection;}public boolean isQUEUE_SAVE() {return QUEUE_SAVE;}public String getMESSAGE_SAVE() {return MESSAGE_SAVE;}
}

生产者：

/**** 提供延时队列发送方法*/public class MQOrderOverTimeQueue {private static final Logger log= LoggerFactory.getLogger(MQOrderOverTimeQueue.class);private RabbitmqConfiguration rabConf;//队列名称//****==================订单延时队列=======================*****////订单延时队列public final String DELAY_QUEUE_NAME = "delay-queue-orderOverTime";//订单延时队列死信交换的交换器名称public final String EXCHANGENAME = "exchange-orderOverTime";//订单延时队列死信的交换器路由keypublic final String ROUTINGKEY = "routingKey-orderOverTime";private Channel delayChannel;//延时队列连接通道private Channel consumerChannel;//消费队列连接通道public void init() throws Exception{//创建连接通道delayChannel=rabConf.getConnection().createChannel();delayChannel.confirmSelect();//开启confirm事务/**创建处理延时消息的延时队列*/Map <String,Object> arg = new HashMap <String,Object>();//配置死信交换器arg.put("x-dead-letter-exchange",EXCHANGENAME); //交换器名称//死信交换路由key （交换器可以将死信交换到很多个其他的消费队列，可以用不同的路由key 来将死信路由到不同的消费队列去）arg.put("x-dead-letter-routing-key", ROUTINGKEY);delayChannel.queueDeclare(DELAY_QUEUE_NAME, rabConf.isQUEUE_SAVE(), false, false, arg);}/*** 方法描述: 发送延迟订单处理消息* @param msg 消息内容 （订单号或者json格式字符串）* @param overTime 消息存活时间* @throws Exception*/public void sendMessage(String msg,Long overTime) throws Exception{AMQP.BasicProperties properties = new AMQP.BasicProperties.Builder().expiration(overTime.toString()) //设置消息存活时间（毫秒）.build();delayChannel.basicPublish("",DELAY_QUEUE_NAME, properties, msg.getBytes("UTF-8"));if (delayChannel.waitForConfirms()){log.info("send success");}else{log.info("send false");}}public RabbitmqConfiguration getRabConf() {return rabConf;}public void setRabConf(RabbitmqConfiguration rabConf) {this.rabConf = rabConf;}public MQOrderOverTimeQueue() {RabbitmqConfiguration rf= new RabbitmqConfiguration();try {rf.init();this.rabConf = rf;this.init();} catch (Exception e) {e.printStackTrace();}}}

消费者：

*** 延时队列接收，项目启动时，会默认启动*/@Component
public class MQOrderOverTimeRecv {private static final Logger log=LoggerFactory.getLogger(MQOrderOverTimeRecv.class);private RabbitmqConfiguration rabConf;@Resourceprivate ShopOrderMapper shopOrderMapper;@Resourceprivate ShopGoodsSpecidMapper shopGoodsSpecidMapper;//队列名称//****==================订单延时队列=======================*****////订单延时队列public final String DELAY_QUEUE_NAME = "delay-queue-orderOverTime";//订单延时消费队列public final String CONSUME_QUEUE_NAME = "consume-queue-orderOverTime";//订单延时队列死信交换的交换器名称public final String EXCHANGENAME = "exchange-orderOverTime";//订单延时队列死信的交换器路由keypublic final String ROUTINGKEY = "routingKey-orderOverTime";private Channel consumerChannel;//消费队列连接通道public void init() throws Exception{//创建连接通道// delayChannel=rabConf.getConnection().createChannel();consumerChannel=rabConf.getConnection().createChannel();//创建交换器consumerChannel.exchangeDeclare(EXCHANGENAME,"direct");/**创建消费队列*/consumerChannel.queueDeclare(CONSUME_QUEUE_NAME, rabConf.isQUEUE_SAVE(), false, false, null);//参数1:绑定的队列名  参数2:绑定至哪个交换器  参数3:绑定路由keyconsumerChannel.queueBind(CONSUME_QUEUE_NAME, EXCHANGENAME,ROUTINGKEY);//最多接受条数 0为无限制，每次消费消息数(根据实际场景设置)，true=作用于整channel,false=作用于具体的消费者consumerChannel.basicQos(0,10, false);//创建消费队列的消费者Consumer consumer = new DefaultConsumer(consumerChannel) {@Overridepublic void handleDelivery(String consumerTag, Envelope envelope,AMQP.BasicProperties properties, byte[] body)throws IOException  {String message = new String(body, "UTF-8");try {//业务逻辑处理ConsumeMessage(message);//确认消息已经消费  参数2（true=设置后续消息为自动确认消费  false=为手动确认）consumerChannel.basicAck(envelope.getDeliveryTag(), false);}catch (Exception e) {e.printStackTrace();}}};boolean flag=false;//是否手动确认消息  true 是  false否consumerChannel.basicConsume(CONSUME_QUEUE_NAME, flag, consumer);}/**** 方法描述:监听队列consume-queue-orderOverTime中的消息，用于更新商品订单* 业务逻辑说明: TODO(总结性的归纳方法业务逻辑)* @param msg 消费消息（订单号，或特定格式json字符串）* @throws InterruptedException*/public void ConsumeMessage(String msg) throws InterruptedException {sout("处理业务”);}}public RabbitmqConfiguration getRabConf() {return rabConf;}public void setRabConf(RabbitmqConfiguration rabConf) {this.rabConf = rabConf;}}

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