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！

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