8、服务发现&服务消费者Feign

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);

 

}