springcloud+Feign服务调用

本文主要是介绍springcloud+Feign服务调用，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

springcloud+Feign服务调用

1.简介

之前我们在搭建Ribbon负载均衡的时候，服务调用采用的RestTemplate。

相关链接：https://blog.csdn.net/u013071014/article/details/111361176

@RequestMapping(path = "/getConsumer", method = RequestMethod.GET)public String getConsumer() {String result = restTemp.getForObject("http://springcloud-provider1/provider/getProvider", String.class);return result;}

访问URL是采用字符串拼接的方式，但是如果input 参数有很多，拼接起来就相当麻烦。

使用Feign可以简化服务调用。

2.Feign的使用

2.1.前置工作

1.Eureka server

https://blog.csdn.net/u013071014/article/details/111031306

2.服务提供者

https://blog.csdn.net/u013071014/article/details/111361176

2.2.Feign的配置

1.在parent项目右键，New—> Maven Module，名称命名为springcloud-consumer2

2.在springcloud-consumer2 的pom.xml文件中新增依赖

<packaging>jar</packaging><dependencies><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-netflix-eureka-client</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><!-- OpenFeign在Feign的基础上支持了Spring MVC的注解，如@RequesMapping等等。OpenFeign的@FeignClient可以解析SpringMVC的@RequestMapping注解下的接口--><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-openfeign</artifactId></dependency>
</dependencies>

3.配置application.yml

server:port: 8092

4.在主启动类加上 @EnableFeignClients注解，开启Spring Cloud Feign的支持功能。

package com.springcloud;import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.cloud.openfeign.EnableFeignClients;@SpringBootApplication
@EnableEurekaClient
@EnableFeignClients
public class SpringCloudConsumerApplication {public static void main(String[] args) {// TODO Auto-generated method stubSpringApplication.run(SpringCloudConsumerApplication.class, args);}}

5.创建接口，添加@FeignClient注解，name属性为服务提供者的服务名

package com.springcloud.service;import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;@FeignClient(name = "springcloud-provider1")
public interface ProviderFeignClient {@RequestMapping(value = "/provider/getProvider", method = RequestMethod.GET)public String getProvider();
}

6.创建controller

package com.springcloud.controller;import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;import com.springcloud.service.ProviderFeignClient;@RestController
@RequestMapping(path = "/consumer")
public class ConsumerController {@Autowiredprivate ProviderFeignClient providerFeignClient;@RequestMapping(value = "/getConsumer", method = RequestMethod.GET)public String getConsumer() {return this.providerFeignClient.getProvider();}
}

7.启动eureka server，三个provider和consumer2，访问api测试
在这里插入图片描述

多次call API访问，我们会发现返回结果以轮询的方式出现。事实如此， Feign 中本身已经集成了Ribbon依赖和自动配置，因此我们不需要额外引入依赖，也不需要再注册RestTemplate 对象。

8.代码结构
在这里插入图片描述

3.Feign + Hystrix

1.在springcloud-consumer2的pom.xml文件中新增依赖

<dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
</dependency>

2.修改springcloud-consumer2的application.yml配置文件

server:port: 8092# 开启Feign的Hystrix支持，默认是false  
feign:hystrix:enabled: true

3.在主启动类添加@EnableHystrix注解

package com.springcloud;import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.cloud.netflix.hystrix.EnableHystrix;
import org.springframework.cloud.openfeign.EnableFeignClients;@SpringBootApplication
@EnableEurekaClient
@EnableFeignClients
@EnableHystrix
public class SpringCloudConsumerApplication {public static void main(String[] args) {// TODO Auto-generated method stubSpringApplication.run(SpringCloudConsumerApplication.class, args);}}

4.新建一个类，实现FeignClient接口或FallbackFactory接口。使用FallbackFactory的好处在于可以获取到触发断路器的异常信息。下面我们以FallbackFactory为例。

package com.springcloud.service;import org.springframework.stereotype.Component;import feign.hystrix.FallbackFactory;@Component
public class ProviderFeignClientFallbackFactory implements FallbackFactory<ProviderFeignClient>{@Overridepublic ProviderFeignClient create(Throwable cause) {// TODO Auto-generated method stubreturn new ProviderFeignClient() {@Overridepublic String getProvider() {// TODO Auto-generated method stubreturn "发生熔断!!! 异常信息: " + cause.getMessage();}};}}

5.修改FeignClient接口，在属性中加上FallbackFactory处理类

package com.springcloud.service;import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;@FeignClient(name = "springcloud-provider1", fallbackFactory = ProviderFeignClientFallbackFactory.class)
public interface ProviderFeignClient {@RequestMapping(value = "/provider/getProvider", method = RequestMethod.GET)public String getProvider();
}

6.启动eureka server，provider和consumer2，访问api返回正常
在这里插入图片描述

7.为了方便测试异常捕获，我们将provider 抛出一个异常，再次call API测试

package com.springcloud.controller;import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;@RestController
@RequestMapping(path = "/provider")
public class ProviderController {@RequestMapping(path = "/getProvider", method = RequestMethod.GET)public String getProvider() throws Exception {throw new Exception("For Test");//return "Provider1";}
}