011 @Retryable的使用

一：概述

　　在调用第三方接口或者使用mq时，会出现网络抖动，连接超时等网络异常，所以需要重试。

　　为了使处理更加健壮并且不太容易出现故障，后续的尝试操作，有时候会帮助失败的操作最后执行成功。

　　例如，由于网络故障或数据库更新中的DeadLockLoserException导致Web服务或RMI服务的远程调用可能会在短暂等待后自行解决。为了自动执行这些操作的重试，Spring Batch具有RetryOperations策略。不过该重试功能从Spring Batch 2.2.0版本中独立出来，变成了Spring Retry模块。

二：示例

1.pom

        <dependency>
            <groupId>org.springframework.retry</groupId>
            <artifactId>spring-retry</artifactId>
        </dependency>
        <dependency>
            <groupId>org.aspectj</groupId>
            <artifactId>aspectjweaver</artifactId>
        </dependency>

2.配置类

　　只有启用@EnabelRetry才行，写在配置类或者启动类上都是可以的

package com.jun.web.config;

import org.springframework.context.annotation.Configuration;
import org.springframework.retry.annotation.EnableRetry;

@Configuration
@EnableRetry
public class RetryConfig {
}

3.服务类

　　一般将其加到服务类上就行，服务类一般写主要逻辑

package com.jun.web.annotation;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.retry.annotation.Backoff;
import org.springframework.retry.annotation.Recover;
import org.springframework.retry.annotation.Retryable;
import org.springframework.stereotype.Service;

import java.time.LocalTime;

@Service
public class PayService {
    private Logger logger = LoggerFactory.getLogger(getClass());

    private final int totalNum = 100000;

    @Retryable(value = Exception.class, maxAttempts = 3, backoff = @Backoff(delay = 2000L, multiplier = 1.5))
    public int minGoodsnum(int num) throws Exception {
        logger.info("减库存开始" + LocalTime.now());
        try {
            int i = 1 / 0;
        } catch (Exception e) {
            logger.error("illegal");
        }
        if (num <= 0) {
            throw new IllegalArgumentException("数量不对");
        }
        logger.info("减库存执行结束" + LocalTime.now());
        return totalNum - num;
    }

    @Recover
    public int recover(Exception e) {
        logger.warn("减库存失败！！！" + LocalTime.now());
        //记日志到数据库
        return totalNum;
    }
}

4.测试

package com.jun.web.annotation;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class PayController {
    @Autowired
    private PayService payService;

    @GetMapping("/retry")
    public String getNum() throws Exception {
        int i = payService.minGoodsnum(-1);
        System.out.println("===="+i);
        return "succeess";
    }
}

5.结果

2019-08-23 10:27:46.702 DEBUG 16036 --- [nio-8080-exec-5] o.s.web.servlet.DispatcherServlet        : GET "/retry", parameters={}
2019-08-23 10:27:46.702 DEBUG 16036 --- [nio-8080-exec-5] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped to public java.lang.String com.jun.web.annotation.PayController.getNum() throws java.lang.Exception
2019-08-23 10:27:46.703  INFO 16036 --- [nio-8080-exec-5] com.jun.web.annotation.PayService        : 减库存开始10:27:46.703
2019-08-23 10:27:46.703 ERROR 16036 --- [nio-8080-exec-5] com.jun.web.annotation.PayService        : illegal
2019-08-23 10:27:48.703  INFO 16036 --- [nio-8080-exec-5] com.jun.web.annotation.PayService        : 减库存开始10:27:48.703
2019-08-23 10:27:48.703 ERROR 16036 --- [nio-8080-exec-5] com.jun.web.annotation.PayService        : illegal
2019-08-23 10:27:51.704  INFO 16036 --- [nio-8080-exec-5] com.jun.web.annotation.PayService        : 减库存开始10:27:51.704
2019-08-23 10:27:51.704 ERROR 16036 --- [nio-8080-exec-5] com.jun.web.annotation.PayService        : illegal
2019-08-23 10:27:51.704  WARN 16036 --- [nio-8080-exec-5] com.jun.web.annotation.PayService        : 减库存失败！！！10:27:51.704
====100000
2019-08-23 10:27:51.704 DEBUG 16036 --- [nio-8080-exec-5] m.m.a.RequestResponseBodyMethodProcessor : Using 'text/html', given [text/html, application/xhtml+xml, image/webp, image/apng, application/signed-exchange;v=b3, application/xml;q=0.9, */*;q=0.8] and supported [text/plain, */*, text/plain, */*, application/json, application/*+json, application/json, application/*+json]
2019-08-23 10:27:51.704 DEBUG 16036 --- [nio-8080-exec-5] m.m.a.RequestResponseBodyMethodProcessor : Writing ["succeess"]
2019-08-23 10:27:51.705 DEBUG 16036 --- [nio-8080-exec-5] o.s.web.servlet.DispatcherServlet        : Completed 200 OK
2019-08-23 10:27:51.714 DEBUG 16036 --- [nio-8080-exec-6] o.s.web.servlet.DispatcherServlet        : GET "/favicon.ico", parameters={}
2019-08-23 10:27:51.715 DEBUG 16036 --- [nio-8080-exec-6] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped to ResourceHttpRequestHandler [class path resource [META-INF/resources/], class path resource [resources/], class path resource [static/], class path resource [public/], ServletContext resource [/], class path resource []]
2019-08-23 10:27:51.718 DEBUG 16036 --- [nio-8080-exec-6] o.s.web.servlet.DispatcherServlet        : Completed 200 OK

三：说明

1.@Retryable参数的意思说明

value：抛出指定异常才会重试
include：和value一样，默认为空，当exclude也为空时，默认所以异常
exclude：指定不处理的异常
maxAttempts：最大重试次数，默认3次
backoff：重试等待策略，默认使用@Backoff，@Backoff的value默认为1000L，我们设置为2000L；multiplier（指定延迟倍数）默认为0，表示固定暂停1秒后进行重试，如果把multiplier设置为1.5，则第一次重试为2秒，第二次为3秒，第三次为4.5秒。

2.Recover注解

　　当重试耗尽时，RetryOperations可以将控制传递给另一个回调，即RecoveryCallback。Spring-Retry还提供了@Recover注解，用于@Retryable重试失败后处理方法，此方法里的异常一定要是@Retryable方法里抛出的异常，否则不会调用这个方法。

　　从上面的结果上可以看出来。

原文地址：https://www.cnblogs.com/juncaoit/p/11398547.html