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

• 例子2

  @org.springframework.stereotype.Servicepublic 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

  @Servicepublic 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