SpringCloud(四):服務消費(Feign)
一、Feign介紹 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。
二、Feign消費者
pom.xml
<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-eureka-server</artifactId> </dependency> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-feign</artifactId> </dependency> application.properties
spring.application.name=hello-consumer-feign server.port=8031
eureka.client.serviceUrl.defaultZone=http://localhost:8001/eureka/ Feign客戶端
package cn.saytime.service;
import org.springframework.cloud.netflix.feign.FeignClient; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RequestParam;
@FeignClient("hello-service") public interface HelloService {
@RequestMapping("hello") String hello (@RequestParam(value = "name") String name) ; } 注意點:這裡hello-service大小寫都可以,預設會轉成大寫
還有一點要注意:
@RequestParam(value = "name") 這裡必須是這樣配置,如果不配置或者配置的value=name1或者是其他值,相當於傳其他引數key過去,在這裡傳錯的話,會返回hello, null,因為hello-service介面拿不到name的值。
啟動類
package cn.saytime;
import cn.saytime.service.HelloService; import org.springframework.beans.factory.annotation.Autowired; 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; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RestController;
@SpringBootApplication @EnableDiscoveryClient @EnableFeignClients @RestController public class HelloConsumerFeignApplication {
public static void main(String[] args) { SpringApplication.run(HelloConsumerFeignApplication.class, args); }
@Autowired private HelloService helloService;
@RequestMapping("hello") public String hello(String name){ return helloService.hello(name); } } 三、測試 同樣的,先啟動eureka-server:8001, 以及hello-service:8011,8012,然後訪問:
http://localhost:8031/hello?name=feign
結果:
hello, feign 同樣的多次訪問,hello-service:8011,8012日誌都有列印呼叫資訊,表示也實現了負載均衡。