使用Filter拦截器如何实现请求跨域转发

因为公司项目需求,项目中前端请求需要通过一个类似中转的服务转发(请求在该服务中会重新包装一些通用参数),在使用Filter实现转发后特做一次记录

package com.unicloud.cce.Filter;

import com.alibaba.fastjson.JSON;
import com.unicloud.cce.common.RestfulEntity;
import com.unicloud.cce.service.CloudosService;
import org.apache.commons.io.IOUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.*;
import org.springframework.stereotype.Component;
import org.springframework.util.AntPathMatcher;
import org.springframework.util.StringUtils;
import org.springframework.web.client.RestTemplate;

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.*;

/**
 * @author skyxt
 * Created 2019-06-11 18:46
 * Email skyxt.yang@gmail.com
 */
@WebFilter(filterName = "authFilter", urlPatterns = { "/*" })
@Component
public class RequestFilter implements Filter {


    //该处配置需要转发的路径
    public static final Set<String> FILTER_URL = Collections.unmodifiableSet(new HashSet<>(Arrays.asList(
            "/config/*"
    )));

    @Autowired
    private RestTemplate restTemplate;
    @Autowired
    private CloudosService cloudosService;


    private final static Logger logger = LoggerFactory.getLogger(RequestFilter.class);

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {

    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        if (!(request instanceof HttpServletRequest) || !(response instanceof HttpServletResponse)) {
            return;
        }
        HttpServletRequest req = (HttpServletRequest) request;
        HttpServletResponse rsp = (HttpServletResponse) response;
        AntPathMatcher matcher = new AntPathMatcher();
        Optional<String> cloudIp = Optional.empty();
//        for (String url : FILTER_URL) {
//            if (matcher.match(url, req.getRequestURI().substring(req.getContextPath().length()))) {
//                cloudIp = cloudosService.cloudosList("", "").stream().filter(cloudos ->
//                        cloudos.getId().equals(((HttpServletRequest) request).getHeader("cloudId"))
//                ).map(Cloudos::getCloudIp).findFirst();
//            }
//        }
        cloudIp = Optional.of("localhost");
        if (cloudIp.isPresent()) {
            switch (req.getMethod()) {
                case "GET": {
                    request(req, rsp, HttpMethod.GET, cloudIp.get());
                    break;
                }
                case "POST": {
                    request(req, rsp, HttpMethod.POST, cloudIp.get());
                    break;
                }
                case "PUT": {
                    request(req, rsp, HttpMethod.PUT, cloudIp.get());
                    break;
                }
                case "PATCH": {
                    request(req, rsp, HttpMethod.PATCH, cloudIp.get());
                    break;
                }
                case "DELETE": {
                    request(req, rsp, HttpMethod.DELETE, cloudIp.get());
                    break;
                }
                default:{
                    logger.error("unknow request method:" + req.getMethod());
                    rsp.setCharacterEncoding("UTF-8");
                    try (PrintWriter out = rsp.getWriter()) {
                        out.write("请求方法未知");
                    } catch (Exception e1) {
                        logger.error(e1.getMessage() + e1);
                    }
                }

            }
        } else {
            chain.doFilter(request, response);
        }
    }

    @Override
    public void destroy() {

    }

    private void request(HttpServletRequest req, HttpServletResponse rsp, HttpMethod method, String cloudIp) throws IOException {
        rsp.setCharacterEncoding("UTF-8");
        String requestBody = IOUtils.toString(req.getInputStream(), "UTF-8");
        Object body = null;
        if (StringUtils.hasText(requestBody)) {
            body = JSON.parse(requestBody);
        }
        HttpHeaders headers = new HttpHeaders();
        Enumeration<String> headerNames = req.getHeaderNames();
        while (headerNames.hasMoreElements()) {
            String name = headerNames.nextElement();
            headers.add(name, req.getHeader(name));
        }
        String url;
        if (StringUtils.hasText(req.getQueryString())) {
            url = String.format(
                    "http://%s:15120%s?%s",
                    cloudIp,
                    req.getRequestURI().substring(req.getContextPath().length()),
                    req.getQueryString()
                    );
        } else {
            url = String.format(
                    "http://%s:15120%s",
                    cloudIp,
                    req.getRequestURI().substring(req.getContextPath().length())
            );
        }
        HttpEntity<Object> httpEntity = new HttpEntity<>(body, headers);
        ResponseEntity<RestfulEntity> exchange = null;
        try {
            exchange = restTemplate.exchange(
                    url,
                    method,
                    httpEntity,
                    RestfulEntity.class
            );
        } catch (Exception e) {
            logger.error(e.getMessage(), e);
            try (PrintWriter out = rsp.getWriter()) {
                out.write("请求异常");
            } catch (Exception e1) {
                logger.error(e1.getMessage() + e1);
            }
        }
        if (exchange != null) {
            exchange.getStatusCode();
            rsp.setStatus(exchange.getStatusCodeValue());
            exchange.getHeaders().entrySet().stream().forEach(entry -> {
                String value = entry.getValue().toString();
                rsp.addHeader(entry.getKey(), value.substring(1, value.length()-1));
            });
            try (PrintWriter out = rsp.getWriter()) {
                out.write(JSON.toJSONString(exchange.getBody()));
            } catch (Exception e) {
                logger.error(e.getMessage(), e);
            }
        } else {
            logger.info("error: URL:" + "http://" + cloudIp + ":15120" + req.getRequestURI().substring(req.getContextPath().length()));
            try (PrintWriter out = rsp.getWriter()) {
                out.write("请求异常");
            } catch (Exception e1) {
                logger.error(e1.getMessage() + e1);
            }
        }

    }
}
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