SpringCloud 使用Fegin实现客户端负载均衡

fegin基于Netflix Fegin实现，整合了ribbon+Hystrix，是做为客户端负载均衡的一个插件，它比ribbon更加简洁，不用拼写那么长的url和参数，它自身是一个声明式的伪http客户端，写起来更加思路清晰和方便，通过对接口的注解，使得调用接口就像调用方法一样简单。

1，创建配置fegin模块

<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>

打开fegin的application.properties进行配置

server.port=8702
#设置服务名
spring.application.name=fegin
#设置服务注册中心的URL，本服务要向该服务注册中心注册自己
eureka.client.serviceUrl.defaultZone= http://localhost:8080/eureka

启动类添加注解 @EnableFeignClients 启用fegin功能 @EnableEurekaClient 启用服务注册客户端功能

@EnableFeignClients
@EnableEurekaClient
@SpringBootApplication
public class FeginApplication {

    public static void main(String[] args) {
        SpringApplication.run(FeginApplication.class, args);
    }
}

创建service：FeginClients 添加注解：@FeignClient(value=“client-A”) 使用ribbon进行负载，应用服务名称是client-A，demo2，3服务名称都是client-A； 创建两个测试接口，带参数和不带参数的

@FeignClient(value="client-A")
public interface FeignClients {
    @RequestMapping(value = "/hello")
    public String hello();
    @RequestMapping(value = "/hello2")
    public String hello(@RequestParam("name") String name);
}

创建接口调用FeginController

@RestController
public class FeginController {

    @Resource
    FeignClients feignClients;
    @RequestMapping("/hello")
    public String hello() {
        return feignClients.hello();
    }
    @RequestMapping("/hello2")
    public String hello2(@RequestParam("name") String name) {
        return feignClients.hello(name);
    }
}

2，client创建测试接口

demo2添加代码：

@RequestMapping("/hello")
    public String hello(HttpServletRequest request) {
       return "demo2";
    }
    @RequestMapping("/hello2")
    public String hello(HttpServletRequest request,@RequestParam String name) {
        return "demo2+"+name;
    }

demo3添加代码：

@RequestMapping("/hello")
    public String hello(HttpServletRequest request) {
       return "demo3";
    }
    @RequestMapping("/hello2")
    public String hello(HttpServletRequest request,@RequestParam String name) {
        return "demo3+"+name;
    }

3，测试

依次启动demo1，fegin，demo2，demo3 输入http://localhost:8080，degin和两台client都已经注册上 分别输入http://localhost:8702/hello 和http://localhost:8702/hello2?name=123进行刷新测试 说明fegin客户端负载已经成功。