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。