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SpringClould服务与消费者Feign


上一篇文章,讲述了如何通过RestTemplate+Ribbon去消费服务,这篇文章主要讲述如何通过Feign去消费服务。

一、Feign简介

Feign是一个声明式的伪Http客户端,它使得写Http客户端变得更简单。使用Feign,只需要创建一个接口并注解。它具有可插拔的注解特性,可使用Feign 注解和JAX-RS注解。Feign支持可插拔的编码器和解码器。Feign默认集成了Ribbon,并和Eureka结合,默认实现了负载均衡的效果。

简而言之:

  • Feign 采用的是基于接口的注解
  • Feign 整合了ribbon

二、准备工作

继续用上一节的工程, 启动eureka-server,端口为8761; 启动service-hi 两次,端口分别为8762 、8773.

三、创建一个feign的服务

新建一个spring-boot工程,取名为serice-feign,在它的pom文件引入Feign的起步依赖spring-cloud-starter-feign、Eureka的起步依赖spring-cloud-starter-eureka、Web的起步依赖spring-boot-starter-web,代码如下:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>

<groupId>com.forezp</groupId>
<artifactId>service-feign</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>

<name>service-feign</name>
<description>Demo project for Spring Boot</description>

<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-eureka</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-feign</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>Dalston.RC1</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>

<repositories>
<repository>
<id>spring-milestones</id>
<name>Spring Milestones</name>
<url>https://repo.spring.io/milestone</url>
<snapshots>
<enabled>false</enabled>
</snapshots>
</repository>
</repositories>


</project>

 在工程的配置文件application.yml文件,指定程序名为service-feign,端口号为8765,服务注册地址为​​http://localhost:8761/eureka/​​ ,代码如下:

eureka:
client:
serviceUrl:
defaultZone: http://localhost:8761/eureka/
server:
port: 8765
spring:
application:
name: service-feign

 在程序的启动类ServiceFeignApplication ,加上@EnableFeignClients注解开启Feign的功能:

package com.zntg.servicefeign;
/**
* 一、Feign简介
* Feign是一个声明式的伪Http客户端,它使得写Http客户端变得更简单。使用Feign,只需要创建一个接口并注解。
* 它具有可插拔的注解特性,可使用Feign 注解和JAX-RS注解。Feign支持可插拔的编码器和解码器。
* Feign默认集成了Ribbon,并和Eureka结合,默认实现了负载均衡的效果。
* 简而言之:
* Feign 采用的是基于接口的注解
* Feign 整合了ribbon
*/
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.netflix.feign.EnableFeignClients;
/**
* @Description: SpringCloud教程 | 第三篇: 服务消费者(Feign)
* 用法:在程序的启动类ServiceFeignApplication ,加上@EnableFeignClients注解开启Feign的功能
* @Author: zhengyunfei q q 号:541122375
* @Date: 2018/7/3
* @time:11:03
*/
@SpringBootApplication
@EnableDiscoveryClient
@EnableFeignClients
public class ServiceFeignApplication {

public static void main(String[] args) {
SpringApplication.run(ServiceFeignApplication.class, args);
}
}

 定义一个feign接口,通过@ FeignClient(“服务名”),来指定调用哪个服务。比如在代码中调用了service-hi服务的“/hi”接口,代码如下:

package com.zntg.servicefeign.service;

import org.springframework.cloud.netflix.feign.FeignClient;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;

/**
* @Description: 定义一个feign接口,通过@ FeignClient(“服务名”),来指定调用哪个服务。比如在代码中调用了service-hi服务的“/hi”接口,代码如下:
* @Author: zhengyunfei q群号:541122375
* @Date: 2018/7/3
* @time:11:05
*/
@FeignClient(value="service-hi")
public interface SchedualServiceHi {
@RequestMapping(value = "/hi",method = RequestMethod.GET)
String sayHiFromClientOne(@RequestParam(value = "name") String name);
}

 在Web层的controller层,对外暴露一个”/hi”的API接口,通过上面定义的Feign客户端SchedualServiceHi 来消费服务。代码如下:

package com.zntg.servicefeign.web;

import com.zntg.servicefeign.service.SchedualServiceHi;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

/**
* @program: zntg_clould_v1
* @description:在Web层的controller层,对外暴露一个”/hi”的API接口,通过上面定义的Feign客户端SchedualServiceHi 来消费服务。代码如下:
* @author: zhengyunfei
* @create: 2018-07-03 11:08
**/
@RestController
public class HiController {
@Autowired
SchedualServiceHi schedualServiceHi;
/**
* @Description: sayHi api接口
* @Author: zhengyunfei q q 群:541122375
* @Date: 2018/7/3
* @time:11:09
*/
@RequestMapping(value = "/hi",method = RequestMethod.GET)
public String sayHi(@RequestParam String name){
return schedualServiceHi.sayHiFromClientOne(name);
}
}

 启动程序,多次访问​​http://localhost:8765/hi?name=forezp​​,浏览器交替显示:

hi forezp,i am from port:8762

hi forezp,i am from port:8763

 

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