# 创建服务消费者（Feign）
# 概述
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
Feign采用的是基于接口的注解Feign整合了ribbon
# 创建服务消费者
创建一个工程名为 hello-spring-cloud-web-admin-feign 的服务消费者项目，pom.xml 配置如下：
<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>com.starmcc</groupId>
<artifactId>hello-spring-cloud-dependencies</artifactId>
<version>1.0.0-SNAPSHOT</version>
<relativePath>../hello-spring-cloud-dependencies/pom.xml</relativePath>
</parent>
<artifactId>hello-spring-cloud-web-admin-feign</artifactId>
<packaging>jar</packaging>
<name>hello-spring-cloud-web-admin-feign</name>
<url>http://www.starmcc.com</url>
<inceptionYear>2019-Now</inceptionYear>
<dependencies>
<!-- Spring Boot Begin -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-tomcat</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-thymeleaf</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-actuator</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<!-- Spring Boot End -->
<!-- Spring Cloud Begin -->
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-openfeign</artifactId>
</dependency>
<!-- Spring Cloud End -->
<!-- 解决 thymeleaf 模板引擎一定要执行严格的 html5 格式校验问题 -->
<dependency>
<groupId>net.sourceforge.nekohtml</groupId>
<artifactId>nekohtml</artifactId>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<configuration>
<mainClass>com.funtl.hello.spring.cloud.web.admin.feign.WebAdminFeignApplication</mainClass>
</configuration>
</plugin>
</plugins>
</build>
</project>
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主要是增加了 Feign 的依赖
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-openfeign</artifactId>
</dependency>
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# Application
通过 @EnableFeignClients 注解开启 Feign 功能
@SpringBootApplication
@EnableDiscoveryClient
@EnableFeignClients
public class WebAdminFeignApplication {
public static void main(String[] args) {
SpringApplication.run(WebAdminFeignApplication.class, args);
}
}
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# application.yml
spring:
application:
name: hello-spring-cloud-web-admin-feign
thymeleaf:
cache: false
mode: LEGACYHTML5
encoding: UTF-8
servlet:
content-type: text/html
server:
port: 8765
eureka:
client:
serviceUrl:
defaultZone: http://localhost:8761/eureka/
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# 创建 Feign 接口
通过 @FeignClient("服务名") 注解来指定调用哪个服务。代码如下：
@FeignClient(value = "hello-spring-cloud-service-admin")
public interface AdminService {
@RequestMapping(value = "hi", method = RequestMethod.GET)
public String sayHi(@RequestParam(value = "message") String message);
}
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# 创建测试用的 Controller
@RestController
public class AdminController {
@Autowired
private AdminService adminService;
@RequestMapping(value = "hi", method = RequestMethod.GET)
public String sayHi(@RequestParam String message) {
return adminService.sayHi(message);
}
}
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# 测试访问
在浏览器上多次访问 http://localhost:8765/hi?message=HelloFeign
浏览器交替显示：
Hi，your message is :"HelloFeign" i am from port：8762
Hi，your message is :"HelloFeign" i am from port：8763
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请求成功则表示我们已经成功实现了 Feign 功能来访问不同端口的实例