【微服务架构】SpringCloud之Feign

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什么是Feign

Feign 是一个声明web服务客户端，这便得编写web服务客户端更容易，使用Feign 创建一个接口并对它进行注解，它具有可插拔的注解支持包括Feign注解与JAX-RS注解，Feign还支持可插拔的编码器与解码器，Spring Cloud 增加了对 Spring MVC的注解，Spring Web 默认使用了HttpMessageConverters, Spring Cloud 集成 Ribbon 和 Eureka 提供的负载均衡的HTTP客户端 Feign.

实现

1、先要启动EureKaserver工程（注册中心）和SpringCloud-Service工程（服务生产者）
可以参考：https://blog.csdn.net/u012081441/article/details/80708060

2、创建一个maven工程SpringCloud-Feign

pom.xml文件

<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.fit</groupId>
  <artifactId>SpringCloud-Feign</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <!-- SpringBoot父类依赖引用 -->
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.2.RELEASE</version>
        <relativePath />
    </parent>
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
    </properties>
    <dependencies>
    <!--eureka server -->
        <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>
    </dependencies>
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>Dalston.RC1</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>
    <repositories>
        <repository>
            <id>spring-milestones</id>
            <name>Spring Milestones</name>
            <url>https://repo.spring.io/milestone</url>
            <snapshots>
                <enabled>false</enabled>
            </snapshots>
        </repository>
    </repositories>

</project>

application.yml文件配置

eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:8888/eureka/
server:
  port: 8765
spring:
  application:
    name: SpringCloud-Feign

定义服务接口类UserService.java，使用@FeignClient(“SpringCloud-Service”)注解来绑定该接口对应SpringCloud-Service服务

@FeignClient("SpringCloud-Service")
public interface UserService {
    @RequestMapping(value ="getUser")
    public Map<String,Object> getUser();
}

在web层中调用上面定义的UserController

@RestController
public class UserController {
    @Resource
    private UserService userService;
    @RequestMapping(value ="getUser")
    public Map<String,Object> getUser(){
        return userService.getUser();
    }
}

在应用主类中通过@EnableFeignClients注解开启Feign功能

启动文件FeignApp.java

@SpringBootApplication
@EnableEurekaClient
@EnableFeignClients
public class FeignApp {
    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        SpringApplication.run(FeignApp.class, args);
    }
}

源码下载