在eclipse上部署springcloud小例子--第二篇:服務消費者(feign)
上一篇文章,講述瞭如何通過RestTemplate+Ribbon去消費服務,這篇文章主要講述如何通過Feign去消費服務。
一、Feign簡介
Feign是一個宣告式的偽Http客戶端,它使得寫Http客戶端變得更簡單。使用Feign,只需要建立一個介面並註解。它具有可插拔的註解特性,可使用Feign 註解和JAX-RS註解。Feign支援可插拔的編碼器和解碼器。Feign預設集成了Ribbon,並和Eureka結合,預設實現了負載均衡的效果。
簡而言之:
Feign 採用的是基於介面的註解
Feign 整合了ribbon,具有負載均衡的能力
整合了Hystrix,具有熔斷的能力
二、準備工作
繼續用上一節的工程, 啟動eureka-server,埠為8761; 啟動eureka-client兩次,埠分別為8762 、8763.
三、建立一個feign的服務
新建一個spring-boot工程,取名為serice-feign,在它的pom檔案引入Feign的起步依賴spring-cloud-starter-feign、Eureka的起步依賴spring-cloud-starter-netflix-eureka-client、Web的起步依賴spring-boot-starter-web,程式碼如下:
<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>
在工程的配置檔案application.yml檔案,指定程式名為service-feign,埠號為8765,服務註冊地址為http://localhost:8761/eureka/ ,程式碼如下:
eureka:
client:
serviceUrl:
defaultZone: http://localhost:8761/eureka/
server:
port: 8765
spring:
application:
name: service-feign
在程式的啟動類ServiceFeignApplication ,加上@EnableFeignClients註解開啟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);
}
}
定義一個feign介面,通過@ FeignClient(“服務名”),來指定呼叫哪個服務。比如在程式碼中呼叫了eureka-client服務的“/hi”介面,程式碼如下:
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層的controller層,對外暴露一個"/hi"的API介面,通過上面定義的Feign客戶端SchedualEurekaClient 來消費服務。程式碼如下:
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);
}
}
啟動程式,多次訪問http://localhost:8765/hi?name=springcloud,瀏覽器交替顯示:
hi ! springcloud,i am from port:8762
hi ! springcloud,i am from port:8763