“Hello everyone! ”
Feign简介
Feign 主要有三大特征如下：
- 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
第一步：创建服务集群
这一篇文章基于上一篇文章的工程， 启动EurekaServer工程；启动EurekaClient工程，它的端口为8762；复制工程EurekaClient，并将EurekaClient的配置文件的端口改为9873,并启动，这时你会 发现：EurekaClient在EurekaServer注册了2个实例，这就相当于一个小的集群。
第二步：创建一个服务消费者：
右键工程->创建创建module->选择spring initialir->web->web,cloud discovery->eureka discovery,cloud routing->feign,然后一直下一步就行了。
创建完成后：
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<?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>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.1.1.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.test</groupId>
<artifactId>service-feign</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>service-feign</name>
<description>Demo project for Spring Boot</description>
<properties>
<java.version>1.8</java.version>
<spring-cloud.version>Greenwich.RC2</spring-cloud.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<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-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>
<repositories>
<repository>
<id>spring-milestones</id>
<name>Spring Milestones</name>
<url>https://repo.spring.io/milestone</url>
</repository>
</repositories>
</project>
配置appication.yml文件：
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server:
port: 9874
eureka:
client:
service-url:
defaultZone: http://localhost:9871/eureka/
spring:
application:
name: service-feign
第三步 配置启动类
在工程的启动类中,通过@EnableDiscoveryClient向服务中心注册；并且加上@EnableFeignClients注解开启Feign的功能
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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);
}
}
第四步：写一个测试类HelloService
通过@ FeignClient（“服务名”），来指定调用哪个服务。比如在代码中调用了eureka-server服务的“/hello”接口，代码如下：
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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 HelloService {
@RequestMapping(value = "/hello",method = RequestMethod.GET)
String sayHelloFromClient(@RequestParam(value = "name") String name);
}
第五步：写一个测试类controller
在controller中用调用HelloService 的方法，代码如下：
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import com.test.servicefeign.service.HelloService;
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 HelloController {
@Autowired
HelloService helloService;
@GetMapping(value = "/hello")
public String sayHello(@RequestParam String name){
return helloService.sayHelloFromClient(name);
}
}
启动工程
打开 http://localhost:9874/hello?name=handsomeman ，你会在浏览器上看到交替显示：
hello: handsomeman,i am from port:9872
hello: handsomeman,i am from port:9873
这说明当我们通过调用eureka-server服务的“/hello”接口时，已经做了负载均衡，访问了不同的端口的服务实例。
源码下载：
https://github.com/mochengyanliu/SpringCloudLearn/tree/master/section3
