spring cloud 教学四（服务消费者（Feign））

上一篇文章，讲述了如何通过RestTemplate+Ribbon去消费服务，这篇文章主要讲述如何通过Feign去消费服务。

Feign 采用的是基于接口的注解

准备工作

继续用上一节的工程，启动eureka-server（服务注册中心），端口为8080; 启动service-client两次，端口分别为8081、8082.

创建一个feign的服务

新建一个spring-boot工程，取名为serice-feign，在它的pom文件引入Feign的起步依赖spring-cloud-starter-feign、Eureka的起步依赖spring-cloud-starter-eureka、Web的起步依赖spring-boot-starter-web，代码如下：

<?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.wzy</groupId>
	<artifactId>serice-feign</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>jar</packaging>

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

	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.0.5.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>Finchley.SR1</spring-cloud.version>
	</properties>

	<dependencies>
		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-starter-netflix-eureka-server</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-web</artifactId>
		</dependency>
		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-starter-openfeign</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>

在工程的配置文件application.yml文件，指定程序名为service-feign，端口号为8084，服务注册地址为http://localhost:8080/eureka/ ，代码如下：

spring.application.name=service-feign
server.port=8084

eureka.client.serviceUrl.defaultZone=http://localhost:8080/eureka/

在程序的启动类ServiceFeignApplication ，加上@EnableFeignClients注解开启Feign的功能：

@SpringBootApplication
@EnableDiscoveryClient
@EnableFeignClients
public class SericeFeignApplication {

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

定义一个feign接口，通过@ FeignClient（“服务名”），来指定调用哪个服务@RequestMapping指定服务的哪个接口。比如在代码中调用了service-client服务的“/login”接口，代码如下：

@FeignClient(value = "EUREKA-CLIENT")
public interface SchedualServiceHi {
    @RequestMapping(value = "/login",method = RequestMethod.GET)
    String sayHiFromClientOne(@RequestParam(value = "name") String name);
}

在Web层的controller层，对外暴露一个”/login”的API接口，通过上面定义的Feign客户端SchedualServiceHi 来消费服务。代码如下：

@RestController
public class HiController {

    @Autowired
    SchedualServiceHi schedualServiceHi;

    @RequestMapping(value = "/login",method = RequestMethod.GET)
    public String sayHi(@RequestParam String name){
        return schedualServiceHi.sayHiFromClientOne(name);
    }
}

启动程序，多次访问http://localhost:8084/login?name=forezp,浏览器交替显示：

what do you do 8081

what do you do 8082

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