java使用Feign实现声明式Restful风格调用

2019-11-26 09:03:47

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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@RestControllerpublic 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@SpringBootApplicationpublic 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);}

@RestControllerpublic 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@RestControllerpublic 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

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