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,了解springcloud架构可以加求求:三五三六二四七二五九,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-netflix-eureka-client、Web的起步依赖spring-boot-starter-web,代码如下:
class="xml" name="code"><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>com.forezp</groupId> <artifactId>sc-f-chapter3</artifactId> <version>0.0.1-SNAPSHOT</version> </parent> <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:
@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service-hi服务的“/hi”接口,代码如下:
@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:
1 2 3 4 5 6 7 8 9 10monospace; margin: 0px !important; padding: 0px !important; border-radius: 0px !important; background: none !important; border: 0px !important; float: none !important; line-height: 1.1em !important; overflow: visible !important; vertical-align: baseline !important; width: auto !important; font-size: 13px !important;">@RestController
public
?class?HiController?{
????
//编译器报错,无视。?因为这个Bean是在程序启动的时候注入的,编译器感知不到,所以报错。
????
@Autowired
????
SchedualServiceHi?schedualServiceHi;
????
@GetMapping(value?=?
"/hi"
)
????
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
?
?