8、服务发现&服务消费者Feign

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spring cloud的Netflix中提供了两个组件实现软负载均衡调用，分别是Ribbon和Feign。上一篇和大家一起学习了Ribbon。

Ribbon ：Spring Cloud Ribbon是基于HTTP和TCP的客户端负载工具，它是基于Netflix Ribbon实现的，它可以在客户端配置 ribbonServerList（服务端列表），然后轮询请求以实现均衡负载。

Feign ：spring cloud feign 是一个使用起来更加方便的 HTTP 客戶端。 在使用ribbon时，通常会使用RestTemplate实现对http请求的封装，形成了模板化的调用方法。spring cloud feign在此基础上做了进一步的封装，Feign是一种声明式、模板化的HTTP客户端。在Spring Cloud中使用Feign, 可以做到使用HTTP请求远程服务时能与调用本地方法一样的编码体验，完全感知不到这是远程方法，更感知不到这是个HTTP请求。

1、 新建项目sc-eureka-client-consumer-feign，对应的pom.xml文件如下

<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">
    <modelVersion>4.0.0</modelVersion>

    <groupId>spring-cloud</groupId>
    <artifactId>sc-eureka-client-consumer-feign</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>sc-eureka-client-consumer-feign</name>
    <url>http://maven.apache.org</url>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.4.RELEASE</version>
    </parent>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>Finchley.RELEASE</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>

        </dependencies>
    </dependencyManagement>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>

    <dependencies>
    
        <!-- 说明是一个 eureka client -->
        <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>
        
        <!-- <dependency> 
                <groupId>org.springframework.cloud</groupId> 
                <artifactId>spring-cloud-starter-feign</artifactId> 
                <version>1.4.5.RELEASE</version> 
           </dependency> -->

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
        </dependency>
        
    </dependencies>
</project>

备注：spring cloud 2.x后spring-cloud-starter-feign已经被标识为过期，推荐使用spring-cloud-starter-openfeign

2、 新建spring boot启动类ConsumerFeignApplication.java

package sc.consumer;

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

}

3、 创建配置文件bootstrap.yml和application.yml，对应的内容如下

bootstrap.yml

server:
  port: 5800

application.yml

spring:
  application:
    name: sc-eureka-client-consumer-feign

eureka:
  client:
    registerWithEureka: true #是否将自己注册到Eureka服务中，默认为true
    fetchRegistry: true #是否从Eureka中获取注册信息，默认为true
    serviceUrl:
      defaultZone: http://localhost:5001/eureka/

4、 编写feign客户端

package sc.consumer.service;

import java.util.Map;

import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.DeleteMapping;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.PutMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;

import sc.consumer.model.User;

@FeignClient(value="sc-eureka-client-provider")
public interface UserService {

    @GetMapping("/user/getUser/{id}")
    Map<String, Object> getUser(@PathVariable(value ="id") Long id);

    @RequestMapping("/user/listUser")
    Map<String, Object> listUser();

    @PostMapping("/user/addUser")
    Map<String, Object> addUser(@RequestBody User user);

    @PutMapping("/user/updateUser")
    Map<String, Object> updateUser(@RequestBody User user);

    @DeleteMapping("/user/deleteUser/{id}")
    Map<String, Object> deleteUser(@PathVariable(value ="id") Long id);

}

5、 分别启动注册中心项目sc-eureka-server和服务提供者sc-eureka-client-provider

6、 启动项目sc-eureka-client-consumer-feign，并验证是否启动成功

方法一

方法二

7、 使用postman验证

查询：

http://127.0.0.1 :5800/feign/user/getUser/4

列表：

http://127.0.0.1 :5800/feign/user/listUser

添加：

http://127.0.0.1 :5800/feign/user/addUser

更新：

http://127.0.0.1 :5800/feign/user/updateUser

删除：

http://127.0.0.1 :5800/feign/user/deleteUser/6

备注：

sc-eureka-client-provider项目的UserController.java 需要修正

源码

https://gitee.com/hjj520/spring-cloud-2.x/tree/master/sc-eureka-client-consumer-feign