Spring Cloud 之 声明式REST客户端 Feign组件

Feign是一个声明式的Web服务客户端。能很简单的调用其他服务的API。并且实现负载均衡。

1、创建Feign模块

在前两篇文章的基础上继续改造工程。
Spring Cloud 之 服务注册与发现 Eureka组件
Spring Cloud 之 负载均衡 Ribbon组件
新建model：service-feign
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.server</groupId>
    <artifactId>feign</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

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

    <parent>
        <groupId>com.cloud</groupId>
        <artifactId>test</artifactId>
        <version>1.0-SNAPSHOT</version>
    </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.RELEASE</spring-cloud.version>
    </properties>

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

配置文件application.yml

eureka:
  client:
    serviceUrl:
      # 注明自己的服务注册中心的地址
      defaultZone: http://localhost:7777/eureka/
server:
  port: 8005
spring:
  application:
    name: service-feign

在应用主类上表明为eureka-client，向服务注册中心注册

@SpringBootApplication
@EnableEurekaClient
//注解开启Feign
@EnableFeignClients
public class FeignApplication {

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

}

创建调用接口FeignService

@Service
@FeignClient(value = "service-hello")
public interface FeignService {

    @RequestMapping(value = "/hi",method = RequestMethod.GET)
    String sayHiFromClientOne(@RequestParam(value = "name") String name);
}

@FeignClient(value = “service-hello”)，value 指明要调用的服务名
Controller

@RestController
public class HiController {

    @Autowired
    FeignService feignService;

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

}

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2、测试

启动service-feign
可以再服务注册中心看到实例：

浏览器多次访问：http://localhost:8005/hi?name=mistra，会交替出现

• hi mistra,i am from port:8002
• hi mistra,i am from port:8003

service-feign远程调用了eureka-client的服务，并且实现了负载均衡。

源码

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