一起来学SpringCloud之 - 断路器Hystrix(Feign)

文章目录
  1. 1. - Hystrix
  2. 2. - 准备工作
    1. 2.1. - battcn-provider
      1. 2.1.1. - pom.xml
      2. 2.1.2. - ProviderApplication.java(有变化)
      3. 2.1.3. - bootstrap.yml
    2. 2.2. - battcn-consumer
      1. 2.2.1. - pom.xml
      2. 2.2.2. - ConsumerApplication
      3. 2.2.3. - HiClient
      4. 2.2.4. - HiController
      5. 2.2.5. - bootstrap.yml
    3. 2.3. - 测试
  3. 3. - 解锁新姿势
    1. 3.1. - 异常处理
      1. 3.1.1. - FeignServiceErrorDecoder
      2. 3.1.2. - 测试
    2. 3.2. - Request 参数传递
      1. 3.2.1. - FeignRequest(consumer)
      2. 3.2.2. - HelloController(provider)
      3. 3.2.3. - 测试
  4. 4. - 说点什么

上一篇中我们讲了 断路器Hystrix(Ribbon) 本章讲解Feign+Hystrix已经Request请求传递,各种奇淫技巧….

- Hystrix

Hystrix支持回退概念:当 断路器 打开或运行错误时,执行默认的代码,给@FeignClient定义一个fallback属性,设置它实现回退的,还需要将您的实现类声明为Spring Bean。

官方文档:http://cloud.spring.io/spring-cloud-static/Dalston.SR2/#spring-cloud-feign-hystrix-fallback

- 准备工作

1.启动Consul
2.创建 battcn-providerbattcn-consumer 如果看了上一章的,可以直接copy代码复用

- battcn-provider

- pom.xml

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<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-consul-discovery</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-actuator</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>

- ProviderApplication.java(有变化)

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@SpringBootApplication
@EnableDiscoveryClient
@RestController
public class ProviderApplication {

@Value("${spring.application.name}")
String applicationName;

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

@GetMapping("/test1")
public String test1() {
return "My Name's :" + applicationName + " Email:1837307557@qq.com";
}

@GetMapping("/test2")
public String test2() {
System.out.println(1/0);
return "hello error";
}
}

- bootstrap.yml

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server:
port: 8765

spring:
application:
name: battcn-provider
cloud:
consul:
host: localhost
port: 8500
enabled: true
discovery:
enabled: true
prefer-ip-address: true

- battcn-consumer

- pom.xml

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<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-feign</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-hystrix</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-actuator</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-consul-discovery</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>

- ConsumerApplication

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@SpringCloudApplication
@EnableFeignClients//开启 FeignClient支持
public class ConsumerApplication {

@Bean
@LoadBalanced
public RestTemplate restTemplate() {
return new RestTemplate();
}

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

}

- HiClient

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package com.battcn.client;

import org.springframework.cloud.netflix.feign.FeignClient;
import org.springframework.stereotype.Component;
import org.springframework.web.bind.annotation.GetMapping;

/**
* @author Levin
* @date 2017-08-07.
*/
@FeignClient(value = "battcn-provider",fallback = HiClient.HiClientFallback.class)
public interface HiClient {

@GetMapping("/test1")
String test1();

@GetMapping("/test2")
String test2();

@Component
class HiClientFallback implements HiClient{
@Override
public String test1() {
return "fallback....";
}

@Override
public String test2() {
return "fallback...";
}
}
}

- HiController

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package com.battcn.controller;

import com.battcn.client.HiClient;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class HiController {
@Autowired
HiClient hiClient;
@GetMapping("/h1")
public String hi() {
return hiClient.test1();
}
@GetMapping("/h2")
public String say() {
return hiClient.test2();
}
}

- bootstrap.yml

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server:
port: 8766

feign:
hystrix:
enabled: true #开启Feign Hystrix 支持

spring:
application:
name: battcn-consumer
cloud:
consul:
host: localhost
port: 8500
enabled: true
discovery:
enabled: true
prefer-ip-address: true

- 测试

启动:battcn-provider

启动:battcn-consumer

访问:http://localhost:8500/ 显示如下代表服务注册成功

查看注册中心

访问:http://localhost:8766/h1

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My Name's :battcn-provider Email:1837307557@qq.com	#正确情况

访问:http://localhost:8766/h2

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fallback...  	#错误情况,阻断输出fallback...

- 解锁新姿势

- 异常处理

画图工具:https://www.processon.com/

异常处理

如果我们FeignClient服务都是内部的,在客户端抛出异常直接往最外层抛出,就不需要在消费者通过硬编码处理了,关键代码(完整代码看GIT)…

battcn-provider 中异常处理

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@ExceptionHandler(value = Exception.class)
@ResponseBody
public ErrorResponseEntity jsonErrorHandler(Exception e, HttpServletResponse rep) throws Exception {
if (e instanceof BattcnException) {
BattcnException exception = (BattcnException) e;
return exception.toErrorResponseEntity();
}
logger.error("服务器未知异常", e);
rep.setStatus(HttpStatus.INTERNAL_SERVER_ERROR.value());
return new ErrorResponseEntity(HttpStatus.INTERNAL_SERVER_ERROR.value(), "服务器未知异常");
}

battcn-consumer 中异常处理

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@ExceptionHandler(value = Exception.class)
@ResponseBody
public ErrorResponseEntity jsonErrorHandler(Exception e, HttpServletResponse rep) throws Exception {
if (e instanceof HystrixBadRequestException) {
HystrixBadRequestException exception = (HystrixBadRequestException) e;
rep.setStatus(HttpStatus.BAD_REQUEST.value());
logger.info("[HystrixBadRequestException] - [" + exception.getMessage() + "]");
JSONObject obj = JSON.parseObject(exception.getMessage());
return new ErrorResponseEntity(obj.getInteger("customCode"), obj.getString("message"));
}
logger.error("服务器未知异常", e);
rep.setStatus(HttpStatus.INTERNAL_SERVER_ERROR.value());
return new ErrorResponseEntity(HttpStatus.INTERNAL_SERVER_ERROR.value(), "服务器未知异常");
}

Hystrix中只有,HystrixBadRequestException 是不会被计数,也不会进入阻断器,所以我们定义一个自己的错误解码器

- FeignServiceErrorDecoder

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package com.battcn.config;

import com.netflix.hystrix.exception.HystrixBadRequestException;
import feign.Response;
import feign.Util;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;
import java.io.IOException;

@Component
public class FeignServiceErrorDecoder implements feign.codec.ErrorDecoder {
static Logger LOGGER = LoggerFactory.getLogger(FeignServiceErrorDecoder.class);
@Override
public Exception decode(String methodKey, Response response) {
try {
if (response.status() >= 400 && response.status() <= 499) {
String error = Util.toString(response.body().asReader());
return new HystrixBadRequestException(error);
}
} catch (IOException e) {
LOGGER.error("[Feign解析异常] - [{}]", e);
}
return feign.FeignException.errorStatus(methodKey, response);
}
}

- 测试

访问:http://localhost:8766/h1

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My Name's :battcn-provider Email:1837307557@qq.com	#正确情况

访问:http://localhost:8766/h2

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{"customCode":400,"message":"请求错误"} 	#抛出异常,而不是进入阻断器

关闭battcn-provider:http://localhost:8766/h1

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fallback...  	#服务down机,阻断输出fallback...

- Request 参数传递

在开发中难免会有 服务之间 请求头传递比如Token,ID,因为我们使用的是FeignClient 的方式,那么我们无法获得HttpServletRequest的上下文,这个时候怎么办呢?通过硬编码是比较low的一种,接下来为各位看官带来简单粗暴的(也就知道这种,还有其它简单的方式欢迎交流….)

参数传递

- FeignRequest(consumer)

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package com.battcn.config;

import feign.RequestInterceptor;
import feign.RequestTemplate;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;
import java.util.UUID;

@Component
public class FeignRequest implements RequestInterceptor {

final Logger LOGGER = LoggerFactory.getLogger(this.getClass().getSimpleName());

@Override
public void apply(RequestTemplate requestTemplate) {
//1.模拟获取request.header参数
String token = UUID.randomUUID().toString().replace("-","").toUpperCase();
LOGGER.info("传递的Token - [{}]",token);
requestTemplate.header("token",token);//模拟将Token放入在 feign.Request对象中

}
}

- HelloController(provider)

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@Value("${spring.application.name}")
String applicationName;

@Autowired
HttpServletRequest request;

@Override
@GetMapping("/test1")
public String test1() {
return "My Name's :" + applicationName + " Token:"+request.getHeader("token");
}

- 测试

日志结果

结果:My Name's :battcn-provider Token:5588551D64C8478BA681A35892A03437 代表我们Token(HttpServletRequest)传递成功…

- 说点什么

画图工具:https://www.processon.com/

本章代码(battcn-provider/consumer):https://git.oschina.net/battcn/battcn-cloud/tree/master/battcn-cloud-hystrix-feign

如有问题请及时与我联系

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