Spring retry基本使用

背景介绍

在实际工作过程中，重试是一个经常使用的手段。比如MQ发送消息失败，会采取重试手段，比如工程中使用RPC请求外部服务,可能因为网络
波动出现超时而采取重试手段......可以看见重试操作是非常常见的一种处理问题,系统设计的手段

而在之前我们项目中处理重拾操作依赖MQ自身的重试机制,但是这种机制不是很灵活,如果某些功能没有使用MQ的话,那么就不是那么方便了,而本文介绍的
Spring-Retry却能够以一种很优雅的方式解决这种问题,当然目前版本的Spring-retry还不是完美的,还是有待改进的.不过已经很不错了.

基本使用

• 例子1

  @Configuration
  @EnableRetry
  public class Application {
  
      @Bean
      public Service service() {
          return new Service();
      }
  
  }
  
  @Service
  class Service {
      @Retryable(RemoteAccessException.class)
      public void service() {
          // ... do something
      }
      @Recover
      public void recover(RemoteAccessException e) {
         // ... panic
      }
  }

• 例子2

  @org.springframework.stereotype.Service
  public class Service1 {
  
      @Retryable(value = {RemoteAccessException.class, RuntimeException.class},
              maxAttempts = 2,
              backoff = @Backoff(value = 2000))
      public void service() {
          System.out.println("do some things");
          // this exception will just trigger recover1, do not trigger recover3
          throw new RemoteAccessException("remote access exception");
          // this exception will just trigger recover2
  //        throw new RuntimeException("runtime exception");
  
  //        System.out.println("do another things");
      }
  
      // 如果使用注解的话,这个recover貌似只能写在本类中,我测试了如果将recover方法写在
      // recoverService中,好像找不到
  
      @Recover
      public void recover1(RemoteAccessException e) {
          System.out.println(e.getMessage());
          System.out.println("do recover operation1");
      }
  
      @Recover
      public void recover2(RuntimeException e) {
          System.out.println(e.getMessage());
          System.out.println("do recover operation2");
      }
  
      @Recover
      public void recover3(RemoteAccessException e) {
          System.out.println(e.getMessage());
          System.out.println("do recover operation3");
      }
  
  }

• 例子3

  @Service
  public class Service2 {
  
      public void test(){
          final RetryTemplate retryTemplate = new RetryTemplate();
          final SimpleRetryPolicy policy = new SimpleRetryPolicy(3, Collections.<Class<? extends Throwable>, Boolean>
                  singletonMap(Exception.class, true));
          FixedBackOffPolicy fixedBackOffPolicy = new FixedBackOffPolicy();
          fixedBackOffPolicy.setBackOffPeriod(100);
          retryTemplate.setRetryPolicy(policy);
          retryTemplate.setBackOffPolicy(fixedBackOffPolicy);
          final RetryCallback<Object, Exception> retryCallback = new RetryCallback<Object, Exception>() {
              public Object doWithRetry(RetryContext context) throws Exception {
                  System.out.println("do some thing");
                  //设置context一些属性,给RecoveryCallback传递一些属性
                  context.setAttribute("key1", "value1");
                  System.out.println(context.getRetryCount());
                  throw new Exception("exception");
  //                return null;
              }
          };
  
          // 如果RetryCallback执行出现指定异常, 并且超过最大重试次数依旧出现指定异常的话,就执行RecoveryCallback动作
          final RecoveryCallback<Object> recoveryCallback = new RecoveryCallback<Object>() {
              public Object recover(RetryContext context) throws Exception {
                  System.out.println("do recory operation");
                  System.out.println(context.getAttribute("key1"));
                  return null;
              }
          };
  
          try {
              final Object execute = retryTemplate.execute(retryCallback, recoveryCallback);
          } catch (Exception e) {
              e.printStackTrace();
          }
      }
  }

参考资料

• spring-retry
• spring-retry-showcase
• Spring retry – ways to integrate with your project

http://www.cnblogs.com/rollenholt/p/4711441.html