前言：

在上一节里，我们学习了ribbon的使用。

我们了解到ribbon是一个客户端负载均衡机制。

而我们今天要讲的Feign呢，也是一款客户端负载均衡机制。

或者这样说，Feign封装了ribbon的负载均衡，实现了面向接口调用服务编程取缔面向服务编程。

ribbon面向服务编程：

@GetMapping("/hello")public List
    
      sayHello() {    List
     
       list = new ArrayList<>();    for(int i=0;i<30;i++) {        list.add(restTemplate.getForObject("http://CL-HELLO-PRODUCER/hello", String.class));    }    return list;}
     
    

feign面向接口编程：

@FeignClient(value="CL-HELLO-PRODUCER")public interface HelloService {        @GetMapping("/hello")    public String sayHello();}

新建一个服务消费者（cl_hello_consumer_feign）：

1.添加依赖

    
        
     
      4.0.0
         
     
      com.xm.cloud
         
     
      cl_hello_consumer_feign
         
     
      0.0.1-SNAPSHOT
         
     
      jar
         
     
      cl_hello_consumer_feign
         
     
      This is a Web about springcloud
         
             
      
       org.springframework.boot
              
      
       spring-boot-starter-parent
              
      
       2.0.6.RELEASE
              
       
          
         
             
      
       UTF-8
              
      
       UTF-8
              
      
       1.8
              
      
       Finchley.SR2
          
         
             
                  
       
        org.springframework.boot
                   
       
        spring-boot-starter-web
               
              
                  
       
        org.springframework.cloud
                   
       
        spring-cloud-starter-netflix-eureka-client
               
              
                  
       
        org.springframework.cloud
                   
       
        spring-cloud-starter-openfeign
               
              
                  
       
        org.springframework.boot
                   
       
        spring-boot-starter-test
                   
       
        test
               
          
         
             
                  
                       
        
         org.springframework.cloud
                        
        
         spring-cloud-dependencies
                        
        
         ${spring-cloud.version}
                        
        
         pom
                        
        
         import
                    
               
          
         
             
                  
                       
        
         org.springframework.boot
                        
        
         spring-boot-maven-plugin
                    
               
          
     
    

2.修改配置

eureka.client.service-url.defaultZone=http://127.0.0.1:7001/eureka/eureka.client.register-with-eureka=false

3.开启注解

package com.xm.cloud;import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;import org.springframework.cloud.client.discovery.EnableDiscoveryClient;import org.springframework.cloud.openfeign.EnableFeignClients;import org.springframework.context.annotation.ComponentScan;@EnableFeignClients@EnableDiscoveryClient@SpringBootApplicationpublic class ClHelloConsumerFeignApplication {    public static void main(String[] args) {        SpringApplication.run(ClHelloConsumerFeignApplication.class, args);    }}

4.添加Service

package com.xm.cloud.service;import org.springframework.cloud.openfeign.FeignClient;import org.springframework.web.bind.annotation.GetMapping;@FeignClient(value="CL-HELLO-PRODUCER")public interface HelloService {        @GetMapping("/hello")    public String sayHello();}

5.添加Controller

package com.xm.cloud.controller;import java.util.ArrayList;import java.util.List;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.web.bind.annotation.GetMapping;import org.springframework.web.bind.annotation.RestController;import com.xm.cloud.service.HelloService;@RestControllerpublic class HelloController {    @Autowired    private HelloService helloService;        @GetMapping("/hello")    public List
    
      sayHello() {        List
     
       list = new ArrayList
      
       ();        for(int i=0;i<10;i++) {            list.add(helloService.sayHello());        }        return list;    }}
      
     
    

6.测试

访问：

0	"Hello Spring Cloud! 001号机器"
1	"Hello Spring Cloud! 003号机器"
2	"Hello Spring Cloud! 002号机器"
3	"Hello Spring Cloud! 001号机器"
4	"Hello Spring Cloud! 003号机器"
5	"Hello Spring Cloud! 002号机器"
6	"Hello Spring Cloud! 001号机器"
7	"Hello Spring Cloud! 003号机器"
8	"Hello Spring Cloud! 002号机器"
9	"Hello Spring Cloud! 001号机器"