Spring Cloud入门教程之服务消费者 Feign（三）(Finchley版本+Boot2.0) - 好文

什么是Feign？

        Feign是受到Retrofit，JAXRS-2.0和WebSocket的影响，它是一个java的到http客户端绑定的开源项目。
Feign的主要目标是将Java Http 客户端变得简单。

推荐博客：

      Feign的源码地址：https://github.com/OpenFeign/feign
<https://github.com/OpenFeign/feign>

     深入理解Feign之源码解析：https://blog.csdn.net/forezp/article/details/73480304
<https://blog.csdn.net/forezp/article/details/73480304>

常见错误：

1、Spring Cloud服务消费者使用Feign，不识别@EnableFeignClients 注解解决办法

查阅资料后是Spring
Cloud对Feign的支持由org.springframework.cloud:spring-cloud-netflix-core 移到org.springframework.cloud:spring-cloud-openfeign-core下。

   报错信息：cannot resolve sysmol EnableFeignClients



    解决方案：

    更改Spring Cloud的版本Finchley.RC2换为Dalston.RC1由于Finchley.RC2使用需要Spring
Boot2.0，这里需要把Spring Boot版本换到1.5即可
<dependencies> <dependency> <groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-dependencies</artifactId>
<version>Dalston.RC1</version> <type>pom</type> <scope>import</scope>
</dependency> </dependencies>



一、建立服务消费者

    1、项目建立可参考上一篇博客：https://blog.csdn.net/zjh_746140129/article/details/80557302
<https://blog.csdn.net/zjh_746140129/article/details/80557302>

    2、项目pom.xml 新增
<dependency> <groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-feign</artifactId> </dependency>
完整pom.xml
<?xml version="1.0" encoding="UTF-8"?> <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>com.serverfeign</groupId>
<artifactId>serverfeign</artifactId> <version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging> <name>serverfeign</name> <description>Demo project
for Spring Boot</description>  <parent> <groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.5.2.RELEASE</version> <relativePath/>  </parent>  <properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<java.version>1.8</java.version> </properties> <dependencies> <dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-eureka</artifactId> </dependency> <dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-feign</artifactId> </dependency> <dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId> </dependency> <dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId> <scope>test</scope>
</dependency> </dependencies> <dependencyManagement>  <dependencies>
<dependency> <groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-dependencies</artifactId>
<version>Dalston.RC1</version> <type>pom</type> <scope>import</scope>
</dependency> </dependencies> </dependencyManagement> <build> <plugins>
<plugin> <groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId> </plugin> </plugins> </build>
<repositories> <repository> <id>spring-milestones</id> <name>Spring
Milestones</name> <url>https://repo.spring.io/milestone</url> <snapshots>
<enabled>false</enabled> </snapshots> </repository> </repositories> </project>

    3、编写服务消费Service和Controller

        通过@ FeignClient（“服务名”），来指定调用哪个服务
package com.serverfeign.serverfeign.service; import
org.springframework.cloud.netflix.feign.FeignClient; import
org.springframework.web.bind.annotation.RequestMapping; import
org.springframework.web.bind.annotation.RequestMethod; import
org.springframework.web.bind.annotation.RequestParam; /** *
通过@FeignClient（“服务名”），来指定调用哪个服务 * Created by zhoujh on 2018/6/04 */
@FeignClient(value = "hello-service") public interface HelloService {
@RequestMapping(value = "/hi",method = RequestMethod.GET) String
sayHiFromClientOne(@RequestParam(value = "name") String name); }



package com.serverfeign.serverfeign.controller;

import com.serverfeign.serverfeign.service.HelloService;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.web.bind.annotation.*;

@RestController

public class HelloController {

@Autowired

HelloService helloService;

@RequestMapping(value = "/hi",method = RequestMethod.GET)

@ResponseBody

public String HiFeign(@RequestParam String name){

return helloService.sayHiFromClientOne(name);

}

}

4、修改配置文件
server.port=8765 spring.application.name=service-feign
eureka.client.service-url.defaultZone=http://localhost:8761/eureka/

5、修改启动类

在程序的启动类ServiceFeignApplication ，加上@EnableFeignClients注解开启Feign的功能
package com.serverfeign.serverfeign; import
org.springframework.boot.SpringApplication; import
org.springframework.boot.autoconfigure.SpringBootApplication; import
org.springframework.cloud.client.discovery.EnableDiscoveryClient; import
org.springframework.cloud.netflix.feign.EnableFeignClients;
@SpringBootApplication @EnableDiscoveryClient @EnableFeignClients public class
ServerfeignApplication { public static void main(String[] args) {
SpringApplication.run(ServerfeignApplication.class, args); } }

二、启动服务注册中心、服务提供者(2个)、服务消费者(Feign)

三、刷新消费者，查看服务提供者后台打印，此时已经完成了消费的负载均衡(这里采用了轮询策略)

Spring Boot与Spring Cloud学习使用可参看笔者博客

       ①Spring Cloud入门教程之服务注册与发现Eureka
<https://blog.csdn.net/zjh_746140129/article/details/80557302>

②Spring Cloud入门教程之服务消费者 Ribbon
<https://blog.csdn.net/zjh_746140129/article/details/80560841>

③Spring Cloud入门教程之服务消费者 Feign
<https://blog.csdn.net/zjh_746140129/article/details/80573571>

       ④Spring Cloud入门教程之断路器 Hystrix
<https://blog.csdn.net/zjh_746140129/article/details/80588584>

       ⑤Spring Cloud入门教程之断路由网关 Zuul
<https://blog.csdn.net/zjh_746140129/article/details/80630849>

       ⑥Spring Cloud入门教程之分布式配置中心 Spring Cloud Config
<https://blog.csdn.net/zjh_746140129/article/details/80632087>

       ⑦idea下新建Spring Boot项目并配置启动
<https://blog.csdn.net/zjh_746140129/article/details/80101122>

       ⑧Spring Boot无法自动注入bean问题解决方案
<https://blog.csdn.net/zjh_746140129/article/details/80156223>

       ⑨idea 设置Spring Boot热部署
<https://blog.csdn.net/zjh_746140129/article/details/80217497>

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