【微服务架构】SpringCloud之Feign(五)

时间 2017-02-16 10:00:51  极客头条

原文  http://www.ccblog.cn/97.htm

主题 Spring Cloud 微服务

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/> <!-- lookup parent from repository -->
</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

可能遇到的问题

启动抛出： Attribute 'value' in annotation [org.springframework.cloud.netflix.feign.FeignClient] must be declared as an @AliasFor [serviceId], not [name].

解决：把spring-cloud-dependencies version升级到Brixton.SR5（netflix-core版本升到1.1.1就好了）

代码地址： https://github.com/zhp8341/SpringCloudDemo

未完待续。。。