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(); } } }
