java使用Feign实现声明式Restful风格调用
作者：simonsfan
一、Feign简介
Feign是netflix开发的声明式、模板化的http客户端，在使用时就像调用本地(服务消费者自己)的方法一般，帮助我们更加优雅的调用服务提供者的API。Feign自身支持springMVC，还整合了Eureka、Ribbon，极大的简化了Feign的使用。就整合Euraka而言，只需和普通的服务配置Eureka server的信息即可。整合Ribbon，就意味着不再需要通过标注@LoadBalanced的实例化后的RestTemplate去调用服务提供者方法了。Feign只需通过简单的定义一个接口即可实现负载均衡。
二、在服务消费者中使用Feign
1、添加Feign依赖
<dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-feign</artifactId> </dependency>
2、创建一个feign接口，并在头部加上@FeignClient注解
import com.simons.cn.util.CommonResult;
import org.springframework.cloud.netflix.feign.FeignClient;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
@FeignClient(name = "user-provider")
public interface UserFeignService {
@RequestMapping(value = "/getuserinfo",method = RequestMethod.GET)
CommonResult getUserByName(@RequestParam(required = false,value = "name") String name);
}
这里的name="user-provider" 会被解析为注册到Eureka server上的其中一个客户端，换句话说就是注册到Eureka中的其中一个服务，利用它可以实现负载均衡。也可以结合value来指定@FeignClient(name="user-provider",value = "http://localhost:8000/")
3、修改Controller，不再调用@LoadBalanced标注的RestTemplate，而是通过标注@FeignClient的自定义接口
import com.simons.cn.UserFeignService;
import com.simons.cn.util.CommonResult;
import lombok.extern.slf4j.Slf4j;
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;
@Slf4j
@RestController
public class TicketFeignController {
@Autowired
private UserFeignService userFeignService;
@GetMapping("/ticketpurchase")
public CommonResult purchaseTicket(@RequestParam(required = false,value = "name") String name){
CommonResult result = userFeignService.getUserByName(name);
return result;
}
}
4、修改启动类，头部添加@EnableFeignClients注解
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.netflix.feign.EnableFeignClients;
@EnableFeignClients
@EnableDiscoveryClient
@SpringBootApplication
public class TicketConsumerFeignApplication {
public static void main(String[] args) {
SpringApplication.run(TicketConsumerFeignApplication.class, args);
}
}
测试:
启动多个user-provider-eureka服务实例，其配置文件中的application.name=user-provider;
启动discovery-eureka服务实例;
启动ticket-consumer-feign服务实例
如上测试结果可以看到ticket-consumer-feign消费者顺利调用user-provider-eureka服务提供者的方法，并且实现了负载均衡。
三、使用Feign构造多参数请求
1、get请求:多个参数就用多个@RequestParam标注几个
@FeignClient(name = "user-provider")
public interface UserFeignService {
@RequestMapping(value = "/getuserinfo",method = RequestMethod.GET)
CommonResult getUserByName(@RequestParam(required = false,value = "name") String name);
}
或者用Map来封装参数
@FeignClient(name="user-provider")
public interface UserServiceFeign {
@RequestMapping(value = "/getuserinfo",method = RequestMethod.GET)
public CommonResult getUserByName(@RequestParam Map<String,Object> map);
}
@RestController
public class TicketController {
@Autowired
private UserServiceFeign userServiceFeign;
@GetMapping("ticketpurchase")
public CommonResult (Long id, String actId) {
Map map = new HashMap<String, Object>();
map.put("id", id);
map.put("actId", actId);
return this.userServiceFeign.getUserByName(map);
}
}
2、post请求就相对简单的多
// 服务消费者方
@FeignClient(name="user-provider")
public interface UserServiceFeign {
@RequestMapping(value="/getuserbyname",method = RequestMethod.POST)
public COmmonResult getUserByName(@RequestBody User user);
}
//服务提供者
@Slf4j
@RestController
public class UserController {
@Autowired
private UserServiceImpl userService;
@GetMapping(value = "/getuserinfo")
public CommonResult getUserInfo(@RuquestBody User user){
List<User> userList = userService.getUserByName(user.getName());
return CommonResult.success(CommonEnum.SUCESS.getCode(), CommonEnum.SUCESS.getMessage(),userList);
}
}
项目的github
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持脚本之家。