【微服务架构】SpringCloud之Feign(五)

Feign简介

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.

声明式REST客户端：Feign

先要启动eureka_register_service工程（注册中心）和biz-service-0工程（服务生产者）

创建一个maven工程eureka_feign_client

pom.xml

<parent>

<groupId>org.springframework.boot</groupId>

<artifactId>spring-boot-starter-parent</artifactId>

<version>1.4.3.RELEASE</version>

<relativePath/> 

</parent>

<properties>

<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>

<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-web</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>Brixton.SR5</version>

<type>pom</type>

<scope>import</scope>

</dependency>

</dependencies>

</dependencyManagement>

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

启动文件FeignApplication.java

@SpringBootApplication

@EnableDiscoveryClient

@EnableFeignClients

public class FeignApplication {

public static void main(String[] args) {

SpringApplication.run(FeignApplication.class, args);

}

定义服务接口类UserClient.java

使用@FeignClient("biz-service-0")注解来绑定该接口对应biz-service-0服务

@FeignClient("biz-service-0")

public interface UserClient {

@RequestMapping(method = RequestMethod.GET, value = "/getuser")

public User getuserinfo();

@RequestMapping(method = RequestMethod.GET, value = "/getuser")

public String getuserinfostr();

@RequestMapping(method = RequestMethod.GET, value = "/info")

public String info();

}

在web层中调用上面定义的UserController，具体如下

@RestController

public class UserController {

@Autowired

UserClient userClient;

@RequestMapping(value = "/getuserinfo", method = RequestMethod.GET)

public User getuserinfo() {

return userClient.getuserinfo();

}

@RequestMapping(value = "/getuserinfostr", method = RequestMethod.GET)

public String getuserinfostr() {

return userClient.getuserinfostr();

}

@RequestMapping(value = "/info", method = RequestMethod.GET)

public String info() {

return userClient.info();

}

application.properties配置变量

spring.application.name=feign-consumer

server.port=8004

eureka.client.serviceUrl.defaultZone=http://localhost:8000/eureka/

访问 http://127.0.0.1:8004/getuserinfo

总结：

其实通过Feign封装了HTTP调用服务方法，使得客户端像调用本地方法那样直接调用方法，类似Dubbo中暴露远程服务的方式，区别在于Dubbo是基于私有二进制协议，而Feign本质上还是个HTTP客户端