學習微服務服務消費者——Feign

微服務之間的調用除了restTemplate+ribbon，還有一種方式就是Feign

1.新建一個feign服務

build.gradle文件

buildscript {
	ext {
		springBootVersion = '2.0.4.RELEASE'
	}
	repositories {
		mavenCentral()
	}
	dependencies {
		classpath("org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}")
	}
}

apply plugin: 'java'
apply plugin: 'eclipse'
apply plugin: 'org.springframework.boot'
apply plugin: 'io.spring.dependency-management'

group = 'com.example'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = 1.8

repositories {
	mavenCentral()
}


ext {
	springCloudVersion = 'Finchley.SR1'
}

dependencies {
	compile('org.springframework.boot:spring-boot-starter-web')
	compile('org.springframework.cloud:spring-cloud-starter-netflix-eureka-client')
	compile('org.springframework.cloud:spring-cloud-starter-openfeign')
	testCompile('org.springframework.boot:spring-boot-starter-test')
}

dependencyManagement {
	imports {
		mavenBom "org.springframework.cloud:spring-cloud-dependencies:${springCloudVersion}"
	}
}

application.yml文件

server:
  port: 8795


spring:
  application:
    name: service-feign


eureka:
  client:
    service-url:
      defaultZone: http://localhost:8791/eureka/

啓動主方法

package com.example.servicefeign;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.cloud.openfeign.EnableFeignClients;

@EnableFeignClients
@EnableEurekaClient
@SpringBootApplication
public class ServiceFeignApplication {

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

定義一個feign接口，經過@ FeignClient（「服務名」），來指定調用哪一個服務。好比在代碼中調用了service-hi服務的「/hi」接口，

SayHiService.java文件

package com.example.servicefeign;

import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

@FeignClient("eureka-client-say-hi")  //要調用的服務名
public interface SayHiService {

    @RequestMapping(value = "/hi", method = RequestMethod.GET) //要調用的服務的接口路由，
    String sayHiFromClient(); //括號裏面，可填充要調用的接口的參數


}

HelloController.java文件

package com.example.servicefeign;


import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class HelloController {




    @Autowired
    SayHiService sayHiService;

    @RequestMapping("/hi")
    public String sayHi(){
        return sayHiService.sayHiFromClient();
    }
}

啓動該項目，訪問http://localhost:8795/hi

和

 

此時發現feign採用基於接口的註解，而且具備負載均衡的功能