springcloud-fegin 组件调用

Spring Cloud Feign 是一个声明式的Web服务客户端，它用注解的方式简化了Web服务的调用。

以下是一个使用Spring Cloud Feign的示例：

1. 添加依赖到你的pom.xml：

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-openfeign</artifactId>
</dependency>

2. 启动类上添加@EnableFeignClients注解：

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.openfeign.EnableFeignClients;
 
@SpringBootApplication
@EnableFeignClients
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

3. 创建一个Feign客户端接口：

import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
 
@FeignClient(name = "remote-service", url = "http://localhost:8080")
public interface RemoteServiceClient {
    @GetMapping("/service")
    String getService(@RequestParam(value = "param") String param);
}

4. 使用Feign客户端：

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
 
@RestController
public class Controller {
 
    @Autowired
    private RemoteServiceClient remoteServiceClient;
 
    @GetMapping("/call-service")
    public String callService(String param) {
        return remoteServiceClient.getService(param);
    }
}

在这个例子中，RemoteServiceClient是一个Feign客户端接口，用来定义远程服务的调用。当你调用callService方法时，Feign会负责向http://localhost:8080/service发起请求，并将结果返回。