优雅！Spring的重试小工具

一、介绍

在日常项目的开发中，避免不了调用第三方服务的情况。

如果是第三方有提供SDK包那还好说，就怕没有，第三方接口还不稳定的情况最恼火了。

这个时候，我们一般都会加上重试机制，手动捕获异常发起重试，不优雅

试试这个spring中的工具spring-retry如何

官网

github地址

二、使用

导入maven依赖，使用的是SpringBoot框架，版本号已经有管理了，直接引入即可。

记得把AOP也引用一下

<dependency>
    <groupId>org.springframework.retry</groupId>
    <artifactId>spring-retry</artifactId>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-aop</artifactId>
</dependency>

在SpringBoot的启动类上加上@EnableRetry注解

package com.banmoon.test;

import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.retry.annotation.EnableRetry;
import org.springframework.scheduling.annotation.EnableScheduling;

@EnableRetry
@EnableScheduling
@MapperScan("com.banmoon.test.mapper")
@SpringBootApplication
public class TestApplication {

    public static void main(String[] args) {
        SpringApplication.run(TestApplication.class, args);
    }

}

编写RetryController.java，里面包含了模拟的server方法，一会我们通过client方法去调用它

package com.banmoon.test.controller;

import com.banmoon.test.obj.dto.ResultData;
import com.banmoon.test.service.RetryService;
import io.swagger.annotations.Api;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.validation.annotation.Validated;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;

@Slf4j
@Validated
@Api(tags = "重试测试")
@RestController
@RequestMapping("retry")
public class RetryController {

    @Autowired
    private RetryService retryService;

    @GetMapping("server")
    public ResultData<String> server(@RequestParam Integer delay) throws TimeoutException {
        try {
            boolean timeout = delay > 5000;
            if (timeout) {
                delay = 5000;
            }
            TimeUnit.MILLISECONDS.sleep(delay);
            if (timeout) {
                throw new TimeoutException();
            }
        } catch (InterruptedException e) {
            log.error("睡眠异常");
        }
        return ResultData.success(delay+"");
    }

    @GetMapping("client")
    public ResultData client(@RequestParam Integer delay) {
        String result = retryService.callServer(delay);
        return ResultData.success(result);
    }

}

client方法用到了RetryService.java

package com.banmoon.test.service;

public interface RetryService {

    String callServer(Integer delay);
}

package com.banmoon.test.service.impl;

import cn.hutool.http.HttpUtil;
import cn.hutool.socket.SocketRuntimeException;
import com.alibaba.fastjson2.JSON;
import com.banmoon.test.obj.dto.ResultData;
import com.banmoon.test.service.RetryService;
import lombok.extern.slf4j.Slf4j;
import org.springframework.retry.annotation.Retryable;
import org.springframework.stereotype.Service;

import java.net.SocketTimeoutException;
import java.util.HashMap;
import java.util.Map;

@Slf4j
@Service
public class RetryServiceImpl implements RetryService {

    @Override
    @Retryable(value = {SocketRuntimeException.class, SocketTimeoutException.class}, maxAttempts = 3)
    public String callServer(Integer delay) {
        log.info("客户端请求服务端，delay：{}", delay);
        Map<String, Object> params = new HashMap<>();
        params.put("delay", delay);
        String result = HttpUtil.get("http://localhost:8089/retry/server", params, 5000);
        ResultData<String> data = JSON.parseObject(result, ResultData.class);
        return data.getData();
    }
}

主要就是这行注解

@Retryable(value = {SocketRuntimeException.class, SocketTimeoutException.class}, maxAttempts = 3)

发起重试的异常，重试的次数

具体可以看文档，或者源码

三、测试

启动服务，发送请求

响应是这样的，我们继续看控制台，成功发起重试

四、最后

在文档的示例中，我们也可以这样发起重试，如下

RetryTemplate template = RetryTemplate.builder()
				.maxAttempts(3)
				.fixedBackoff(1000)
				.retryOn(RemoteAccessException.class)
				.build();

template.execute(ctx -> {
    // ... do something
});