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一、前言

在项目开发时会遇到web端/接口请求第三方服务接口的场景，对web请求来说最后请求的服务地址是一个，避免跨域问题，在微服务场景经常使用gateway等网关服务实现，或者使用nginx代理组件实现，但是不同三方服务有不同的鉴权要求，但是后端服务最好有相同的鉴权；

二、解决思路

在非微服务架构和三方不同鉴权接口的服务场景下，通过过滤器Filter实现请求转发，并使用适配器设计模式，兼容不同的三方服务请求（鉴权），减少重复代码开发，也能监控所有的服务请求，并对所有请求做限流、统计等操作；

三、基于gateway实现

在没有spring-boot-starter-web依赖的场景下可以使用gateway，Spring MVC（基于Servlet的Web应用程序）和Spring Cloud Gateway（基于反应式编程的API网关），但是这两个组件是不兼容的。Spring Cloud Gateway是专为反应式编程设计的，使用Spring WebFlux作为底层框架，而Spring MVC则基于Servlet API。

gateway实现代码：

package com.sk.proxytest;import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;@SpringBootApplication
public class ProxyTestApplication {public static void main(String[] args) {SpringApplication.run(ProxyTestApplication.class, args);}@Beanpublic RouteLocator myRoutes(RouteLocatorBuilder builder) {return builder.routes().route(p -> p.path("/test/**").uri("http://127.0.0.1:8089/api")).build();}}

四、基于过滤器Filter实现

本文主要使用过滤器Filter实现，既能控制代理请求，又能最少开发量；

GET请求结果

POST请求结果

实现源码：

ProxyFilter.java

package com.sk.proxytest.proxy;import com.sk.proxytest.proxy.bean.ProxyParam;
import com.sk.proxytest.proxy.bean.ProxyResult;
import com.sk.proxytest.proxy.strategy.ProxyHandleService;
import com.sk.proxytest.proxy.strategy.ProxyHandleStrategyFactory;
import com.sk.proxytest.proxy.strategy.ProxyStrategyContext;
import lombok.extern.slf4j.Slf4j;
import org.apache.commons.io.IOUtils;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.HttpEntity;
import org.springframework.http.HttpMethod;
import org.springframework.http.ResponseEntity;
import org.springframework.web.client.RestTemplate;import javax.annotation.Resource;
import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Map;@Slf4j
@Configuration
@WebFilter(filterName = "ProxyFilter", urlPatterns = "/proxy/*")
public class ProxyFilter implements Filter {@Resourceprivate RestTemplate restTemplate;@Overridepublic void init(FilterConfig filterConfig) throws ServletException {Filter.super.init(filterConfig);}@Overridepublic void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain chain) throws IOException, ServletException {HttpServletRequest request = (HttpServletRequest) servletRequest;HttpServletResponse response = (HttpServletResponse) servletResponse;String proxyType = request.getHeader("proxy-type");ProxyStrategyContext proxyStrategyContext = new ProxyStrategyContext();ProxyHandleService proxyHandleService = ProxyHandleStrategyFactory.getProxyHandleStrategy(proxyType);proxyStrategyContext.setProxyHandleStrategy(proxyHandleService);ProxyResult proxyResult = proxyStrategyContext.handleProxy(new ProxyParam());boolean flag = true;if (null != proxyResult) {PrintWriter writer = null;try {String body = IOUtils.toString(request.getInputStream());HttpEntity<?> entity = new HttpEntity<>(body, proxyResult.getHeaders());String url = proxyResult.getProxyUrl() + getNewUrl(request);log.info("-----------new-url:{}", url);ResponseEntity<String> responseEntity = restTemplate.exchange(url, HttpMethod.resolve(request.getMethod()), entity, String.class);response.setStatus(responseEntity.getStatusCodeValue());writer = response.getWriter();writer.write(responseEntity.getBody());writer.flush();flag = false;} catch (Exception e) {log.error("------error:{}", e);} finally {if (writer != null) {writer.close();}}}if (flag) {chain.doFilter(request, response);}}@Overridepublic void destroy() {Filter.super.destroy();}//获取被代理的url和参数private String getNewUrl(HttpServletRequest request) {String proxyUrl = request.getRequestURI().replace("/proxy", "");Map<String, String[]> parameterMap = request.getParameterMap();int i = 0;for (Map.Entry<String, String[]> entry : parameterMap.entrySet()) {String key = entry.getKey();String value = entry.getValue()[0];if (i == 0) {proxyUrl = proxyUrl + "?" + key + "=" + value;} else {proxyUrl = proxyUrl + "&" + key + "=" + value;}}return proxyUrl;}
}

ProxyHandleService.java

package com.sk.proxytest.proxy.strategy;import com.sk.proxytest.proxy.bean.ProxyParam;
import com.sk.proxytest.proxy.bean.ProxyResult;public interface ProxyHandleService {ProxyResult proxyHandle(ProxyParam proxyParam);}

AlibabaProxyHandleStrategy.java

package com.sk.proxytest.proxy.strategy;import com.sk.proxytest.proxy.bean.ProxyParam;
import com.sk.proxytest.proxy.bean.ProxyResult;
import org.springframework.http.HttpHeaders;public class AlibabaProxyHandleStrategy implements ProxyHandleService {@Overridepublic ProxyResult proxyHandle(ProxyParam proxyParam) {HttpHeaders headers = new HttpHeaders();//TODO 根据三方服务登录接口获取鉴权信息String token = "token--------";headers.add("token", token);headers.add("Content-Type","application/json");//三方服务ip和portString ip = "127.0.0.1";String port = "8080";String proxyUrl = "http://" + ip + ":" + port;return new ProxyResult(headers, proxyUrl);}
}

ProxyHandleStrategyFactory.java

package com.sk.proxytest.proxy.strategy;import java.util.HashMap;
import java.util.Map;public class ProxyHandleStrategyFactory {private static Map<String, ProxyHandleService> proxyHandleServiceMap;static {proxyHandleServiceMap = new HashMap<>();proxyHandleServiceMap.put("alibaba", new AlibabaProxyHandleStrategy());}public static ProxyHandleService getProxyHandleStrategy(String proxyType){return proxyHandleServiceMap.get(proxyType);}}

ProxyStrategyContext.java

package com.sk.proxytest.proxy.strategy;import com.sk.proxytest.proxy.bean.ProxyParam;
import com.sk.proxytest.proxy.bean.ProxyResult;public class ProxyStrategyContext {private ProxyHandleService proxyHandleService;public void setProxyHandleStrategy(ProxyHandleService proxyHandleService){this.proxyHandleService = proxyHandleService;}public ProxyResult handleProxy(ProxyParam proxyParam){if(proxyHandleService != null){return proxyHandleService.proxyHandle(proxyParam);}return null;}}

五、问题总结

在单机服务中，gateway过于重，并且与springMVC有冲突，nginx代理服务不能同一鉴权，或者同一鉴权太过于麻烦，过滤器Filter+适配器模式正好满足我们业务场景需求；
功能实现的方式选择还是要考虑业务场景。