OpenFeign中动态URl、动态传递接口地址

前言：
在微服务盛行的今天，做接口开发请求第三方服务的接口，大概率会用feign做请求，而feign也是最常用的一种rpc框架；

这里主要是说明在进行feign请求的时候，第三方服务的url和接口如何动态获取。
若是该接口是作为基础服务可能会请求多个第三方使用（我们就是不同分支的代码作为独立项目部署，请求不同的客户接口），不同客户的接口地址可能不同，此时就需要做成动态方式；
若是不常改动，其实也没必要动态了；

常用方式：

通常我们是这么请求第三方接口的：（用feign方式）

import com.zkaw.lxjtest.Dto.User;
import com.zkaw.lxjtest.remoteCall.feign.factory.RemoteFeignFactory;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;

import java.util.List;

/**
 * @Author: Best_Liu
 * @Description:
 * @Date Create in 11:14 2022/7/1
 * @Modified By:
 */
@FeignClient(value = "mybatisPlus", url = "http://127.0.0.1:8090", fallbackFactory = RemoteFeignFactory.class)
public interface RemoteFeignClient {

    @PostMapping("/user/selectListNoPage")
    /*@Headers({"content-type:application/json"})*/
    List<User> test(@RequestBody User user);

}

说明：
请求客户的url是：http://127.0.0.1:8090，
调用客户的具体的目标方法是：/user/selectListNoPage 这个方法

第二种方式：配置文件传参

import com.zkaw.lxjtest.Dto.User;
import com.zkaw.lxjtest.remoteCall.feign.factory.RemoteFeignFactory;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;

import java.util.List;

/**
 * @Author: Best_Liu
 * @Description:
 * @Date Create in 11:14 2022/7/1
 * @Modified By:
 */
@FeignClient(value = "mybatisPlus", url = "${feign.client.url.TestUrl}", fallbackFactory = RemoteFeignFactory.class)
public interface RemoteFeignClient {

    @PostMapping("/user/selectListNoPage")
    /*@Headers({"content-type:application/json"})*/
    List<User> test(@RequestBody User user);

}

然后添加配置文件，比如

在你的 application-dev.yml 文件中

feign:
  client:
    url:
      TestUrl: http://127.0.0.1:8088

第三种方式：调用feign时动态传入

实现了url和目标方法的动态传入

1、目标方法的动态传入

利用@PathVariable注解的特性；

用于接收请求路径中占位符的值

@PathVariable(“xxx”)
通过 @PathVariable 可以将URL中占位符参数{xxx}绑定到处理器类的方法形参中
如：
@RequestMapping(value=”user/{id}/{name}”)
请求路径：http://localhost:8080/hello/show/1/lisi

2、url动态实现

在创建feignclient时设置url地址

所以改造下我们的方法：

import com.zkaw.lxjtest.Dto.User;
import com.zkaw.lxjtest.remoteCall.feign.factory.RemoteFeignFactory;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;

import java.util.List;

/**
 * @Author: Best_Liu
 * @Description:
 * @Date Create in 11:14 2022/7/1
 * @Modified By:
 */
@FeignClient(value = "mybatisPlus", fallbackFactory = RemoteFeignFactory.class)
public interface RemoteFeignClient {

    @PostMapping("{apiName}")
    /*@Headers({"content-type:application/json"})*/
    List<User> test(@PathVariable("apiName") String apiName, @RequestBody User user);

}

feign接口调用方式，createFeignClient是Feign核心部分

import com.zkaw.lxjtest.Dto.User;
import com.zkaw.lxjtest.remoteCall.feign.service.RemoteFeignClient;
import feign.Feign;
import feign.form.spring.SpringFormEncoder;
import feign.optionals.OptionalDecoder;
import org.springframework.beans.factory.ObjectFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.autoconfigure.http.HttpMessageConverters;
import org.springframework.cloud.openfeign.support.ResponseEntityDecoder;
import org.springframework.cloud.openfeign.support.SpringDecoder;
import org.springframework.cloud.openfeign.support.SpringEncoder;
import org.springframework.cloud.openfeign.support.SpringMvcContract;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.List;

/**
 * @Author: Best_Liu
 * @Description:
 * @Date Create in 11:20 2022/7/1
 * @Modified By:
 */
@RestController
@RequestMapping("/feign")
public class feignController {

    @Autowired
    ObjectFactory<HttpMessageConverters> messageConverters;

    private RemoteFeignClient createFeignClient(String url) {
        /*1、在创建Feign客户端的时候最核心的对象是decoder、encoder、contract
        通过跟踪源码与SpringBoot自动创建的Feign对象比较，设置decoder、encoder、
        contract为SpringBoot中自动创建对象相同，然后定义Feign接口的时候，
        各种参数的注解和方法的注解就可以和不动态修改url的相同了
        decoder解码器，对返回的结果进行解码*/
        OptionalDecoder decoder = new OptionalDecoder(new ResponseEntityDecoder(new SpringDecoder(messageConverters)));
        //encoder编码器，对输入的数据进行编码
        SpringEncoder springEncoder = new SpringEncoder(messageConverters);
        SpringFormEncoder encoder = new SpringFormEncoder(springEncoder);
        //该对象是将接口进行解析，方便生成最后调用的网络对象HttpurlConnection
        SpringMvcContract contract = new SpringMvcContract();
        RemoteFeignClient feignClient = Feign.builder()
                .decoder(decoder)
                .encoder(encoder)
                .contract(contract)
                //这个地方的Url可以根据每次调用的时候进行改变
                .target(RemoteFeignClient.class, url);
        return feignClient;
    }

    @PostMapping("/selectListNoPage")
    public List<User> selectListNoPage(@RequestBody User user){
        String apiName = "user/selectListNoPage";
        String url = "http://127.0.0.1:8090";
        RemoteFeignClient remoteFeignClient = createFeignClient(url);
        List<User> users = remoteFeignClient.test(apiName,user);
        return users;
    }

}

结果示例

 fallback方式服务降级

import com.zkaw.lxjtest.Dto.User;
import com.zkaw.lxjtest.remoteCall.feign.service.RemoteFeignClient;
import feign.hystrix.FallbackFactory;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;
import org.springframework.web.bind.annotation.PathVariable;

import java.util.ArrayList;
import java.util.List;

/**
 * @Author: Best_Liu
 * @Description: 服务降级
 * @Date Create in 11:34 2022/7/1
 * @Modified By:
 */
@Component
public class RemoteFeignFactory implements FallbackFactory<RemoteFeignClient> {
    private static final Logger log = LoggerFactory.getLogger(RemoteFeignFactory.class);
    @Override
    public RemoteFeignClient create(Throwable throwable) {
        log.error("服务调用失败:{}", throwable.getMessage());
        return new RemoteFeignClient() {
            @Override
            public List<User> test(@PathVariable("apiName") String apiName, User user) {
                return new ArrayList<>();
            }
        };
    }
}

目前我想到的是这种方式，既可以把url动态配置，请求路径也可实现动态，
如果有其它方式还请留言多交流；