Spring Cloud探路（三）REST 客户端Feign

Declarative REST Client: Feign

​​Feign​​ is a declarative web service client. It makes writing web service clients easier.

如上是Spring Cloud文档中对于Feign的定义，结合之前的两篇博文，在这里我们就可以吧Feign简单的理解为用户（前端）可以直接接触到的REST接口提供者。在Feign中，我们可以方便的访问和使用意已经在Erueka服务器中注册过的服务了。

1、建立maven工程，配置pom.xml文件

 
<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>1.5.2.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>
  </properties>
  <dependencies>
    <dependency>
      <groupId>org.springframework.cloud</groupId>
      <artifactId>spring-cloud-starter-feign</artifactId>
    </dependency>
    <dependency>
      <groupId>org.springframework.cloud</groupId>
      <artifactId>spring-cloud-starter-eureka</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>Camden.SR6</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>

2、建立包及启动类

@Configuration
@ComponentScan
@EnableAutoConfiguration
@EnableEurekaClient
@EnableFeignClients
@SpringBootApplication
public class FeignApplication {
  public static void main(String[] args) {
    SpringApplication.run(FeignApplication.class, args);
  }
}

3、建立接口类，用来调用之前文章中CLIENT-SERVICE1服务的方法hello()

@FeignClient("CLIENT-SERVICE1")
public interface IHello {
    @RequestMapping(value = "/hello",method = RequestMethod.GET)
    String getHello();
}

其中@FeignClient中指定需要调用的微服务的名称，@RequestMapping中指定访问微服务响应接口的路径，如之前微服务的hello方法是通过"/hello"路径访问，那么这里需要配置一致

4、新建Controller类，为前端提供REST接口

@RestController
public class HelloController {
    @Autowired
    private IHello iHello;
    @RequestMapping(value = "gethello",method = RequestMethod.GET)
    public String getHello(){
       return iHello.getHello();
    }
}

5、配置Feign的配置文件，指定Erureka服务器注册地址和访问端口application.yml

server:
  port: 8081
eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:1000/eureka/

 成功！