feign自定义第三方接口；配置化Feign接口URL；调用指定IP的feign服务

最近接手一个项目，各子工程之间通过feign调用；各服务部署在K8S上，通过nacos管理配置；由于服务部署的机器无法开放端口等原因，导致本机服务与测试环境网络端口无法互通，故需要重写feign的调用地址；个人总结的方法有以下几种：

目录

 第一种：feignclient配置URL

第二种：实现RequestInterceptor接口；

第三种：重写feign的client的execute方法；

---

 第一种：feignclient配置URL

        在feignclient里写一个固定地址或者写一个可配置的地址，这样可以在配置文件里指定,这种方式在创建feign客户端的时候就需要规划好。

        1.1 固定地址

@FeignClient(name = "feignCustomerService", url = "http://localhost:8080")
public interface FeignCustomerService {
    /**
     * 请求客户的接口
     */
    @RequestMapping(value = "order/update", method = RequestMethod.POST)
    @Headers(value = "Content-Type: application/json")
    OrderHttpResponse updateOrder(@RequestBody OrderUpdateDTO orderUpdateDTO);
 
}

1.2 可配置的地址

@FeignClient(name = "feignCustomerService", url = "${customer.url}")
public interface FeignCustomerService {
   
    @RequestMapping(value = "test/list", method = RequestMethod.POST)
    @Headers(value = "Content-Type: application/json")
    OrderHttpResponse updateTest(@RequestBody OrderUpdateDTO orderUpdateDTO);
 
}

配置文件配置地址

customer.url=http://localhost:8080

第二种：实现RequestInterceptor接口；

        这种方式具有局限性，在nacos上注册的服务IP与本机IP不一致的时候（连接VPN）可能依旧调不通服务，但是实现RequestInterceptor接口可以处理全局请求（header，身份认证等）

@Component
public class Oauth2TokenRequestInterceptor implements RequestInterceptor {

    @Override
    public void apply(RequestTemplate requestTemplate) {
        // 获取请求中的消息头
        ServletRequestAttributes attributes = (ServletRequestAttributes) RequestContextHolder.getRequestAttributes();
        HttpServletRequest request = attributes.getRequest();
        String requestHeader = request.getHeader(HttpHeaders.AUTHORIZATION);
        if (StringUtils.isNotBlank(requestHeader) && requestHeader.startsWith("Bearer ")) {
            // 将消息头塞入到请求模板中
            requestTemplate.header(HttpHeaders.AUTHORIZATION, requestHeader);
        }
        //重写URL，访问指定服务
        String url = target.url();
        String newUrl = "http://localhost:8080";
        template.target(newUrl );
    }
}

第三种：重写feign的client的execute方法；

        这种方式可以自定义负载均衡的策略，也可以自定义访问指定服务IP，这里以FeignBlockingLoadBalancerClient为例

配置类

package com.***.redirect;

import lombok.Getter;
import lombok.Setter;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.cloud.context.config.annotation.RefreshScope;
import org.springframework.stereotype.Component;

import java.util.Map;

@Getter
@Setter
@RefreshScope
@ConfigurationProperties("localbalance")
@Component
public class LocalFeignPerpreties {
    private Boolean enable;
    private Map rule;
}

配置文件配置内容：

localbalance:
  enable: true
  rule:
    aiflow-sys: http://IP:8888/SERVICE
    aiflow-auth: http://IP:8888/SERVICE

重写FeignBlockingLoadBalancerClient 的execute方法

package com.***.redirect;

import feign.Client;
import feign.Request;
import feign.RequestTemplate;
import feign.Response;
import lombok.extern.slf4j.Slf4j;
import org.apache.commons.lang3.StringUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.client.discovery.DiscoveryClient;
import org.springframework.cloud.loadbalancer.blocking.client.BlockingLoadBalancerClient;
import org.springframework.cloud.netflix.ribbon.SpringClientFactory;
import org.springframework.cloud.openfeign.loadbalancer.FeignBlockingLoadBalancerClient;
import org.springframework.cloud.openfeign.ribbon.CachingSpringLoadBalancerFactory;
import org.springframework.cloud.openfeign.ribbon.LoadBalancerFeignClient;
import org.springframework.context.annotation.Primary;
import org.springframework.util.Assert;
import org.springframework.web.context.request.RequestContextHolder;
import org.springframework.web.context.request.ServletRequestAttributes;
import org.springframework.web.util.UriComponentsBuilder;

import javax.servlet.http.HttpServletRequest;
import java.io.IOException;
import java.net.URI;
import java.net.URLEncoder;
import java.nio.charset.Charset;
import java.util.*;

//@ConditionalOnBean
//@Primary
@Slf4j
public class LocalBlockingLoadBalancerClient extends FeignBlockingLoadBalancerClient {
    private Client delegate;
    private BlockingLoadBalancerClient loadBalancerClient;
    @Autowired
    private LocalFeignPerpreties localFeignPerpreties;

    public LocalBlockingLoadBalancerClient(Client delegate,
                                           BlockingLoadBalancerClient loadBalancerClient) {
        super(delegate, loadBalancerClient);
        this.delegate = delegate;
        this.loadBalancerClient = loadBalancerClient;
    }

    @Override
    public Response execute(Request request, Request.Options options) throws IOException {
        try {
            log.info("feign -> 配置化客户端");
            Boolean enable = localFeignPerpreties.getEnable();
            if (enable) {
                String url = request.url();
                RequestTemplate requestTemplate = request.requestTemplate();
                String name = requestTemplate.feignTarget().name();
                Map urlMap = localFeignPerpreties.getRule();
                if (urlMap != null && urlMap.containsKey(name)) {
                    URI uri = URI.create(url);
                    StringBuffer strbuf = new StringBuffer();
                    strbuf.append(urlMap.get(name)).append(uri.getPath());
                    if (StringUtils.isNotBlank(uri.getQuery())) {
                        strbuf.append("?").append(uri.getQuery());
                    }
                    requestTemplate.target(urlMap.get(name));
                    Map> headers = request.headers();
                    Map> newheaders = new HashMap<>();
                    //处理请求头
                    ServletRequestAttributes attributes = (ServletRequestAttributes) RequestContextHolder.getRequestAttributes();
                    HttpServletRequest attributesRequest = attributes.getRequest();
                    Enumeration headerNames = attributesRequest.getHeaderNames();
                    if (headerNames != null) {
                        while (headerNames.hasMoreElements()) {
                            String element = headerNames.nextElement();
                            String elementVal = attributesRequest.getHeader(element);
                            newheaders.put(element, new ArrayList() {{
                                add(elementVal);
                            }});
                        }
                    }
                    //构建新的request
                    Request newRequest = buildRequest(request, strbuf.toString(), newheaders);
                    return super.getDelegate().execute(newRequest, options);
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        log.info("feign -> 默认客户端");
        return super.execute(request, options);
    }

    protected Request buildRequest(Request request,
                                   String reconstructedUrl,
                                   Map> headers) {
        return Request.create(request.httpMethod(), reconstructedUrl, headers,
                request.body(), Charset.forName("UTF-8"), request.requestTemplate());
    }

}

使配置类和重写的client生效

package com.***.redirect;

import feign.Client;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.cloud.loadbalancer.blocking.client.BlockingLoadBalancerClient;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

//@ConditionalOnProperty(prefix = ReBalancerProperties.prefix,name = "enable",havingValue = "true")
@Configuration
@EnableConfigurationProperties(value = {LocalFeignPerpreties.class})
public class ReBalancerConfiguration {

    @Bean
    public Client feignReBalancer(BlockingLoadBalancerClient discoveryClient) {

        return new LocalBlockingLoadBalancerClient(new Client.Default(null, null),
                discoveryClient);
    }
}

        到这里基本上可以满足重写feign URL的需求了，这个前提条件是代码在application启动类的下一级，如果不在启动类的同级或者下一级，是无法扫描到相关类的，这时我们可以注解完成扫描，需要在启动类上加上相关注解

package com.***.annotation;

import com.***.ReBalancerConfiguration;
import org.springframework.boot.autoconfigure.AutoConfigurationPackage;
import org.springframework.context.annotation.Import;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Import(ReBalancerConfiguration.class)
@AutoConfigurationPackage
public @interface EnableLocalFeignClient {
}