SpringCloud之Feign示例详解

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

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持小牛知识库。