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SpringCloud(六):服务消费者Feign 上

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源码地址：https://github.com/IsResultXaL/springcloud

通过上一节内容介绍与实践，我们已经搭建起微服务架构中的核心组件

服务注册中心
服务提供者
服务消费者
断路器Hystrix
Hystrix仪表板
Turbine集群监控

SpringCloud(五):Turbine集群监控

以下Model基于上一节项目新增

###Spring Cloud Feign

Feign是一个声明式Web Service客户端。使用Feign能让编写Web Service客户端更加简单, 它的使用方法是定义一个接口，然后在上面添加注解，同时也支持JAX-RS标准的注解。Feign也支持可拔插式的编码器和解码器。Spring Cloud对Feign进行了封装，使其支持了Spring MVC标准注解和HttpMessageConverters。Feign可以与Eureka和Ribbon组合使用以支持负载均衡。

创建一个model项目(feign-consumer)

feign-consumer项目的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.caogen</groupId>
  	<artifactId>feign-consumer</artifactId>
  	<version>0.0.1-SNAPSHOT</version>
  	<packaging>jar</packaging>

  	<name>feign-consumer</name>
  	<description>Demo project for Spring Boot</description>

  	<parent>
  		<groupId>org.springframework.boot</groupId>
  		<artifactId>spring-boot-starter-parent</artifactId>
  		<version>1.5.9.RELEASE</version>
  		<relativePath/> <!-- lookup parent from repository -->
  	</parent>

  	<properties>
  		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  		<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
  		<java.version>1.8</java.version>
  		<spring-cloud.version>Edgware.RELEASE</spring-cloud.version>
  	</properties>

  	<dependencies>
  		<dependency>
  			<groupId>org.springframework.boot</groupId>
  			<artifactId>spring-boot-starter-web</artifactId>
  		</dependency>

  		<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-actuator</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>${spring-cloud.version}</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>

  </project>

在应用主类加上@EnableFeignClients注解，开启Feign的支持功能。

package com.caogen.feignconsumer;

  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;

  @EnableFeignClients			//开启Feign的支持功能
  @EnableDiscoveryClient    	//表明该应用是Eureka客户端
  @SpringBootApplication
  public class FeignConsumerApplication {

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

配置application.yml

# 端口设置
  server:
    port: 0

  # 应用名称设置
  spring:
    application:
  	name: feign-consumer

  # 注册中心地址
  eureka:
    client:
  	serviceUrl:
  	  defaultZone: http://localhost:1111/eureka/
    instance:
  	  instance-id: ${spring.application.name}:${random.int[10000,19999]}    # 随机数配置实例ID

  #开启hystrix(要不然降级失败)
  feign:
    hystrix:
  	enabled: true

添加ConsumerService接口，通过@FeignClient注解指定服务名来绑定服务，然后再使用Spring MVC的注解来绑定服务提供的REST接口

package com.caogen.feignconsumer.service;

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

  @FeignClient(name = "eureka-client")   //通过@FeignClient注解指定服务名来绑定服务
  public interface ConsumerService {

  	@RequestMapping(value = "/hello", method = {RequestMethod.GET})   //绑定REAT接口
  	String hello();

  }

添加一个ConsumerController控制器来实现对Feign客户端的调用

package com.caogen.feignconsumer.controller;

  import com.caogen.feignconsumer.service.ConsumerService;
  import org.springframework.web.bind.annotation.GetMapping;
  import org.springframework.web.bind.annotation.RestController;

  import javax.annotation.Resource;

  @RestController
  public class ConsumerController {

  	@Resource
  	ConsumerService consumerService;

  	@GetMapping(value = "/feign-consumer")
  	public String helloConsumer() {
  		return consumerService.hello();
  	}

  }