SpringCloud-声明式Rest调用Feign（四）

前言：一般情况下我们通常使用RestTemplate来实现声明式远程调用，但是当参数过多，那么效率就会变得很低，并且难以维护，所以在微服务当中也有声明式Rest调用的组件Feign

一、Feign简介

　　Feign是Netflix开发的声明式、模板化的http客户端，Feign可以帮我们更加便捷、优雅地调用HTTP API。在SpringCloud中使用Feign非常简单，创建一个接口，并在接口上加上注解，就完成了声明式调用；

二、Feign与SpringCloud的整合简单使用

　　注：本次学习记录是基于之前的Eureka介绍和Ribbon介绍之上实践，这里只展示关键代码，其余代码可在代码示例中查看；

　　1、创建基于Eureka和Ribbon的服务端和两个客户端生产者、消费者：

　　Server：

  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">
  4.0.0

  com.cn
  eureka-ribbon-server
  1.0-SNAPSHOT

  
    UTF-8
    1.8
  

  
    org.springframework.boot
    spring-boot-starter-parent
    1.5.13.RELEASE
  

  
    
      org.springframework.cloud
      spring-cloud-starter-eureka-server
    
  
  
    
      
        org.springframework.cloud
        spring-cloud-dependencies
        Edgware.SR3
        pom
        import
      
    
  
  
  
    
      
        org.springframework.boot
        spring-boot-maven-plugin
      
    
  

pom.xml

server.port=8761
#注意：这两个配置eureka默认为true，要改成false，否则会报错，connot connect server
#表示是否将自己注册在EurekaServer上
eureka.client.register-with-eureka=false
#表示是否从EurekaServer获取注册信息
eureka.client.fetch-registry=false

eureka.client.service-url.defaultZone=http://localhost:8761/eureka/

application.properties

package com.cn;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;

/**
 * @program: springcloud-example
 * @description: 启动类
 * @author: 
 * @create: 2018-06-15 15:43
 **/
@SpringBootApplication
@EnableEurekaServer
public class ServerApplication {


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

}

ServerApplication.java

　　Client生产者：

  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">
  4.0.0

  com.cn
  eureka-ribbon-client2
  1.0-SNAPSHOT

  
    UTF-8
    1.8
  

  
    org.springframework.boot
    spring-boot-starter-parent
    1.5.13.RELEASE
  

  
    
      org.springframework.cloud
      spring-cloud-starter-ribbon
    
    
      org.springframework.cloud
      spring-cloud-starter-eureka
    
  
  
    
      
        org.springframework.cloud
        spring-cloud-dependencies
        Edgware.SR3
        pom
        import
      
    
  
  
  
    
      
        org.springframework.boot
        spring-boot-maven-plugin
      
    
  

pom.xml

server.port=8763
spring.application.name=client-87
eureka.client.service-url.defaultZone=http://localhost:8761/eureka

application.properties

package com.cn;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;

/**
 * @program: springcloud-example
 * @description:
 * @author: 
 * @create: 2018-06-15 16:05
 **/
@SpringBootApplication
@EnableDiscoveryClient
public class ClientApplication {

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

}

ClientApplication.java

package com.cn.contorller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.ResponseBody;

/**
 * @program: springcloud-example
 * @description:
 * @author: 
 * @create: 2018-06-15 16:12
 **/
@Controller
public class ClientController {


    @GetMapping("/getUser")
    @ResponseBody
    public String getUser() {
        System.out.println("获取用户成功");
        return "{\"username\":\"张三\",\"age\":\"10\"}";
    }

}

ClientController.java

　　2、在消费者module中的maven依赖中添加相关依赖库，创建Feign访问接口，并注解，通过识别Eureka提供的应用名称，来找对应的请求路径：

　　pom.xml：

  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">
  4.0.0

  com.cn
  eureka-feign-client
  1.0-SNAPSHOT

  
    UTF-8
    1.8
  

  
    org.springframework.boot
    spring-boot-starter-parent
    1.5.13.RELEASE
  

  
    
      org.springframework.cloud
      spring-cloud-starter-ribbon
    
    
      org.springframework.cloud
      spring-cloud-starter-eureka
    


      org.springframework.cloud
      spring-cloud-starter-feign
    

  
  
    
      
        org.springframework.cloud
        spring-cloud-dependencies
        Edgware.SR3
        pom
        import
      
    
  
  
  
    
      
        org.springframework.boot
        spring-boot-maven-plugin
      
    
  

　　application.properties:

server.port=8762
spring.application.name=client-8762
eureka.client.service-url.defaultZone=http://localhost:8761/eureka/

　　Feign接口：

import org.springframework.cloud.netflix.feign.FeignClient;
import org.springframework.web.bind.annotation.RequestMapping;

@FeignClient(name = "CLIENT-87")
public interface UserFeign {

    @RequestMapping("/getUser")
    public String getUser();

}

FeignController：

package com.cn.controller;

import com.cn.feign.UserFeign;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.client.loadbalancer.LoadBalancerClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

/**
 * @program: springcloud-example
 * @description:
 * @author:
 * @create: 2018-06-15 15:55
 **/
@RestController
public class FeignController {
    @Autowired
    private LoadBalancerClient loadBalancerClient;

    @Autowired
    private RestTemplate restTemplate;

@Autowired
    private UserFeign userFeign;

    @RequestMapping("/getUser")
    public String getUser() {
        return userFeign.getUser();
    }

    @GetMapping("/loadInstance")
    public String loadInstance() {
        ServiceInstance choose = this.loadBalancerClient.choose("client-87");
        System.out.println(choose.getServiceId()+":"+choose.getHost()+":"+choose.getPort());
        return choose.getServiceId() + ":" + choose.getHost() + ":" + choose.getPort();
    }

}

　　在ClientApplication.java启动类中加入@EnableFeignClients注解：

package com.cn;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.cloud.netflix.feign.EnableFeignClients;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;

/**
 * @program: springcloud-example
 * @description:
 * @author: 
 * @create: 2018-06-15 15:51
 **/
@SpringBootApplication
@EnableDiscoveryClient
@EnableFeignClients
public class ClientApplication {


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

    /**
     * @Description:
     * @Param:
     * @return:
     * @Author: 
     * @Date: 2018/6/15
     */
    @Bean
    @LoadBalanced
    public RestTemplate getRestTemplate() {
        return new RestTemplate();
    }

}

　　3、分别启动Server、Client生产者、Client消费者，并调用访问http://localhost:8761、http://localhost:8762/getUser，如图：

 

调用成功！

 

参考书籍：《SpringCloud与Docker微服务架构实战》周力著

代码示例：https://gitee.com/lfalex/springcloud-example（ eureka-feign-client、 eureka-ribbon-server、 eureka-ribbon-client2这三个module）

转载于:https://www.cnblogs.com/lfalex0831/p/9200583.html