1.Retry介绍

Spring Retry

提供了自动重新调用失败的操作的功能。这在错误可能是暂时的（例如瞬时网络故障）的情况下很有用。从2.2.0版本开始，重试功能已从Spring Batch中撤出，成为一个独立的新库：Spring Retry

使用场景

在日常开发过程中，难免会与第三方接口发生交互，例如：短信发送、远程服务调用、争抢锁等场景，当正常调用发生异常时，例如：网络抖动，这些间歇性的异常在一段时候之后会自行恢复，程序为了更加健壮并且更不容易出现故障，需要重新触发业务操作，以防止间歇性的异常对程序照成的影响。

tips：幂等性

非幂等的情况下要小心使用重试。HTTP/1.1中对幂等性的定义是：一次和多次请求某一个资源对于资源本身应该具有同样的结果（网络超时等问题除外）。也就是说，其任意多次执行对资源本身所产生的影响均与一次执行的影响相同。

2.代码工程

实验目标：模拟三方接口异常，触发重试

pom.xml

<?xml version="1.0" encoding="UTF-8"?><project xmlns="http://maven.apache.org/POM/4.0.0"         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">    <parent>        <artifactId>springboot-demo</artifactId>        <groupId>com.et</groupId>        <version>1.0-SNAPSHOT</version>    </parent>    <modelVersion>4.0.0</modelVersion>
    <artifactId>SpringRetry</artifactId>
    <properties>        <maven.compiler.source>8</maven.compiler.source>        <maven.compiler.target>8</maven.compiler.target>    </properties>    <dependencies>
        <dependency>            <groupId>org.springframework.boot</groupId>            <artifactId>spring-boot-starter-web</artifactId>        </dependency>
        <dependency>            <groupId>org.springframework.boot</groupId>            <artifactId>spring-boot-autoconfigure</artifactId>        </dependency>        <dependency>            <groupId>org.springframework.boot</groupId>            <artifactId>spring-boot-starter-test</artifactId>            <scope>test</scope>        </dependency>        <!--retry-->        <dependency>            <groupId>org.springframework.boot</groupId>            <artifactId>spring-boot-starter-web</artifactId>        </dependency>        <dependency>            <groupId>org.springframework.retry</groupId>            <artifactId>spring-retry</artifactId>        </dependency>        <dependency>            <groupId>org.aspectj</groupId>            <artifactId>aspectjweaver</artifactId>        </dependency>
    </dependencies></project>

application.yaml

server:  port: 8088

RemoteApiService.java

@Retryable注解，value值表示当哪些异常的时候触发重试，maxAttempts表示最大重试次数默认为3，delay表示重试的延迟时间，multiplier表示上一次延时时间是这一次的倍数。
@Recover注解，当重试次数达到设置的次数的时候，还是失败抛出异常，执行的回调函数。

package com.et.retry.service;
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.LocalDateTime;import java.time.LocalTime;
@Servicepublic class RemoteApiService {
    private Logger logger = LoggerFactory.getLogger(getClass());
    @Retryable(value = Exception.class,maxAttempts = 3,backoff = @Backoff(delay = 2000,multiplier = 1.5))    public boolean pay(int num) throws Exception{        logger.info("invoke third method");        logger.info("do something... {}", LocalDateTime.now());        //mock exception        if(num==0) {            throw new Exception("error，need retry");        }        return true;
    }    @Recover    public boolean recover(int num) throws Exception {        logger.info("recover ... {},{}", num, LocalDateTime.now());        return false;    }
}

DemoApplication.java

在主类上加上@EnableRetry注解，表示启用重试机制。

package com.et.retry;
import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;import org.springframework.retry.annotation.EnableRetry;
@SpringBootApplication@EnableRetrypublic class DemoApplication {
   public static void main(String[] args) {      SpringApplication.run(DemoApplication.class, args);   }}

以上只是一些关键代码，所有代码请参见下面代码仓库

代码仓库

https://github.com/Harries/springboot-demo

3.测试

编写测试类

package com.et.retry;
import com.et.retry.service.RemoteApiService;import org.junit.After;import org.junit.Before;import org.junit.Test;import org.junit.runner.RunWith;import org.slf4j.Logger;import org.slf4j.LoggerFactory;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.boot.test.context.SpringBootTest;import org.springframework.test.context.junit4.SpringRunner;

@RunWith(SpringRunner.class)@SpringBootTest(classes = DemoApplication.class)public class DemoTests {    private Logger log = LoggerFactory.getLogger(getClass());    @Autowired    RemoteApiService remoteApiService;
    @Before    public void before()  {        log.info("init some data");    }    @After    public void after(){        log.info("clean some data");    }    @Test    public void execute() throws Exception {        log.info("pay result:"+remoteApiService.pay(0));    }
}

运行测试方法，结果如下

2024-04-03 10:35:54.738 INFO 13096 --- [ main] com.et.retry.DemoTests : init some data2024-04-03 10:35:54.756 INFO 13096 --- [ main] com.et.retry.service.RemoteApiService : invoke third method2024-04-03 10:35:54.759 INFO 13096 --- [ main] com.et.retry.service.RemoteApiService : do something... 2024-04-03T10:35:54.7582024-04-03 10:35:56.766 INFO 13096 --- [ main] com.et.retry.service.RemoteApiService : invoke third method2024-04-03 10:35:56.766 INFO 13096 --- [ main] com.et.retry.service.RemoteApiService : do something... 2024-04-03T10:35:56.7662024-04-03 10:35:59.776 INFO 13096 --- [ main] com.et.retry.service.RemoteApiService : invoke third method2024-04-03 10:35:59.776 INFO 13096 --- [ main] com.et.retry.service.RemoteApiService : do something... 2024-04-03T10:35:59.7762024-04-03 10:35:59.776 INFO 13096 --- [ main] com.et.retry.service.RemoteApiService : recover ... 0,2024-04-03T10:35:59.7762024-04-03 10:35:59.776 INFO 13096 --- [ main] com.et.retry.DemoTests : pay result:false2024-04-03 10:35:59.778 INFO 13096 --- [ main] com.et.retry.DemoTests : clean some data

4.引用

https://www.jianshu.com/p/314059943f1c
http://www.liuhaihua.cn/archives/710389.html

ITPub博客

Spring Boot集成Spring Retry快速入门Demo