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,具有负载均衡的能力
整合了Hystrix,具有熔断的能力
二、准备工作
继续用上一节的工程, 启动eureka-server,端口为8761; 启动eureka-client两次,端口分别为8762 、8763.
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-netflix-eureka-client、Web的起步依赖spring-boot-starter-web,代码如下:
<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>
<parent>
<groupId>com.springcloud</groupId>
<artifactId>demo-parent</artifactId>
<version>0.0.1-SNAPSHOT</version>
</parent>
<artifactId>service-feign</artifactId>
<properties>
<maven-jar-plugin.version>2.6</maven-jar-plugin.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-openfeign</artifactId>
</dependency>
</dependencies>
</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.springcloud;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.cloud.openfeign.EnableFeignClients;
@SpringBootApplication
@EnableEurekaClient
@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eureka-client服务的“/hi”接口,代码如下:
package com.springcloud;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
@FeignClient(value="eureka-client")
public interface SchedualEurekaClient {
@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SchedualEurekaClient 来消费服务。代码如下:
package com.springcloud;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class HiController {
@Autowired
private SchedualEurekaClient schedualEurekaClient;
@GetMapping(value="/hi")
public String sayHi(@RequestParam String name){
return schedualEurekaClient.sayHiFromClientOne(name);
}
}
启动程序,多次访问http://localhost:8765/hi?name=springcloud,浏览器交替显示:
hi ! springcloud,i am from port:8762
hi ! springcloud,i am from port:8763