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也支持可拔插式的编码器和解码器。Spring Cloud对Feign进行了封装,使其支持了Spring MVC标准注解和HttpMessageConverters。Feign可以与Eureka和Ribbon组合使用以支持负载均衡。
Feign是一个声明式的Web服务客户端,使得编写Web服务客户端变得非常容易,只需要创建一个接口,然后在上面添加注解即可。而与Ribbon不同的是,通过feign只需要定义服务绑定接口且以声明式的方法,优雅而简单的实现了服务调用。 二、创建一个feign的服务 在原先parent的基础上,新建一个spring-boot moudlel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:
<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.0.3.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.cloud</groupId>
<artifactId>service-feign</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>service-feign</name>
<packaging>jar</packaging>
<description>Demo project for Spring Boot</description>
<properties>
<java.version>1.8</java.version>
<spring-cloud.version>Finchley.RELEASE</spring-cloud.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-openfeign</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>${spring-cloud.version}</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>
</project>
配置application.yml文件,代码如下:
server:
port: 8675
spring:
application:
name: service-feign
eureka:
client:
service-url:
defaultZone: http://localhost:8671/eureka/
feign:
hystrix:
enabled: true
在程序的启动类ServiceFeignApplication ,加上@EnableFeignClients注解开启Feign的功能:
@EnableFeignClients
@EnableEurekaClient
@EnableDiscoveryClient
@SpringBootApplication
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,代码如下:
@FeignClient(value = "eurka-client-a",fallback = FeignServiceHystric.class)
public interface FeignService {
@GetMapping(value = "/hello")
String sayHello(@RequestParam(value = "name") String name);
}
在Web层的controller层,对外暴露一个"/hello"的API接口,通过上面定义的Feign客户端FeignService来消费服务。代码如下:
@RestController
public class FeignController {
@Autowired
FeignService feignService;
@RequestMapping(value = "/hello",method = RequestMethod.GET)
public String sayHello(@RequestParam(value = "name") String name){
return feignService.sayHello(name);
}
}