SpringBoot拦截器实现网页代理服务

实际工作中，需要在内网访问外网，安卓端webview能够显示外网页面。实现方式是公司内网假设了代理服务器，可以转发到外网。可是安卓webview不支持配置代理的功能。所以最终的方案是，webview访问内网的一个后台服务器，后台服务器经过加工代理，最终返回给webview网页页面。
这里的后台服务器，就是用springboot的拦截器实现的，对所有访问该服务器的接口都拦截、代理处理。

比如要真实访问的地址是：https://www.baidu.com
java代理服务器的地址是: http://192.168.110.41:8080 （就是本文自己的服务器部署的地址）
那么webview要加载的url为： http://192.168.110.41:8080/https://www.baidu.com

1、拦截器BootInterceptor 的配置

@Slf4j
public class BootInterceptor implements HandlerInterceptor {

    private String host;

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        URI uri = new URI(request.getRequestURI());

        String path = uri.getPath().substring(1);
        String query = request.getQueryString();
        if (!StringUtils.isEmpty(query)) {
            path = path + "?" + query;
        }
        log.info("BootInterceptor path==>" + path);

        if (path.startsWith("http:") || path.startsWith("https:")) {
            int index = path.indexOf("/", 10);
            host = path.substring(0, index);
        } else {
            path = host + "/" + path;
        }
        log.info("BootInterceptor final path==>" + path);
        String subHost="";
        if (host.startsWith("http://")){
            subHost=host.substring("http://".length());
        }else if (host.startsWith("https://")){
            subHost=host.substring("https://".length());
        }

        ProxyUtils2.Proxy(request, response, path,subHost);

        return false;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {

    }
}

@Configuration
public class BootConfig implements WebMvcConfigurer {
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(new BootInterceptor()).addPathPatterns("/**");
    }
}

2、代理的工具类

ProxyUtils

public class ProxyUtils {

    public static final String ip = "192.168.120.50"; // 代理主机地址（公司的硬件代理服务器地址，外网出口服务器）
    public static final int port = 8000; // 代理主机端口

    public static void Proxy(HttpServletRequest request, HttpServletResponse response, String url, String host) throws Exception {

        URI newUri = new URI(url);
        // 执行代理查询
        String methodName = request.getMethod();
        HttpMethod httpMethod = HttpMethod.resolve(methodName);
        if (httpMethod == null) {
            return;
        }
        SimpleClientHttpRequestFactory factory = new SimpleClientHttpRequestFactory();
        factory.setProxy(new java.net.Proxy(Proxy.Type.HTTP, new InetSocketAddress(ip, port)));
        ClientHttpRequest delegate = factory.createRequest(newUri, httpMethod);

        Enumeration<String> headerNames = request.getHeaderNames();
        // 设置请求头

        while (headerNames.hasMoreElements()) {
            String headerName = headerNames.nextElement();
            Enumeration<String> v = request.getHeaders(headerName);
            List<String> arr = new ArrayList<>();
            while (v.hasMoreElements()) {
                arr.add(v.nextElement());
            }
            if ("host".equals(headerName)) {
                delegate.getHeaders().add("host", host);
            } else {
                delegate.getHeaders().addAll(headerName, arr);
            }
        }
        StreamUtils.copy(request.getInputStream(), delegate.getBody());

        try {
            // 执行远程调用
            ClientHttpResponse clientHttpResponse = delegate.execute();
            response.setStatus(clientHttpResponse.getStatusCode().value());
            // 设置响应头
            clientHttpResponse.getHeaders().forEach((key, value) -> value.forEach(it -> {
                response.setHeader(key, it);
            }));
            StreamUtils.copy(clientHttpResponse.getBody(), response.getOutputStream());
        } catch (Exception exception) {
//测试重定向的代码
            response.setStatus(302);
            response.addHeader("Location", "https://www.sohu.com/a/339180879_100024181");
        }


    }
}

ProxyUtils2

@Slf4j
public class ProxyUtils2 {

   public static final String ip = "192.168.120.50"; // 代理主机地址（公司的硬件代理服务器地址，外网出口服务器）
    public static final int port = 8000; // 代理主机端口

    public static void Proxy(HttpServletRequest httpServletRequest,
                             HttpServletResponse httpServletResponse,
                             String url, String host) throws Exception {

        OkHttpClient httpClient = getHttpClient(ip, port);

        Enumeration<String> headerNames = httpServletRequest.getHeaderNames();
        // 设置请求头
        Headers.Builder headerBuilder = new Headers.Builder();
        while (headerNames.hasMoreElements()) {
            String headerName = headerNames.nextElement();
            Enumeration<String> v = httpServletRequest.getHeaders(headerName);
            StringBuffer arr = new StringBuffer();
            while (v.hasMoreElements()) {
                arr.append(v.nextElement());
            }
            if ("host".equals(headerName)){
                headerBuilder.add("host",host);
            }else {
                headerBuilder.add(headerName, arr.toString());
            }
        }

        Request request = new Request.Builder()
                .get()
                .headers(headerBuilder.build())
                .url(url)
                .build();
        log.info("test request headers==>" + request.headers().toString());
//        StreamUtils.copy(httpServletRequest.getInputStream(), request.body());
        // 执行远程调用
        Response response = httpClient.newCall(request).execute();
        httpServletResponse.setStatus(response.code());
        // 设置响应头
        Headers headers = response.headers();
        for (int i=0;i<headers.size();i++){
            String name = headers.name(i);
            String value = headers.value(i);
            httpServletResponse.setHeader(name, value);
        }
        assert response.body() != null;
        StreamUtils.copy(response.body().byteStream(), httpServletResponse.getOutputStream());

        log.info("test response Status==>" + response.code());
        log.info("test response headers==>" + headers.toString());
//        log.info("test response body==>" + response.body().string());

    }


    private static OkHttpClient getHttpClient(String proxyHost, int proxyPort) {

        Proxy proxy = new Proxy(Proxy.Type.HTTP, new InetSocketAddress(proxyHost, proxyPort));
        OkHttpClient build = new OkHttpClient.Builder()
                .proxy(proxy)
                .connectTimeout(180, TimeUnit.SECONDS)
                .readTimeout(180, TimeUnit.SECONDS)
                .writeTimeout(180, TimeUnit.SECONDS)
                .retryOnConnectionFailure(true)
                .sslSocketFactory(createSSLSocketFactory())
                .hostnameVerifier(new TrustAllHostnameVerifier())
                .followRedirects(false)  //禁制OkHttp的重定向操作，我们自己处理重定向 设置为false时关闭重定向自动处理
                .followSslRedirects(false)
                .build();
        return build;

    }

    private static class TrustAllHostnameVerifier implements HostnameVerifier {
        public boolean verify(String hostname, SSLSession session) {
            return true;
        }
    }

    private static SSLSocketFactory createSSLSocketFactory() {
        SSLSocketFactory ssfFactory = null;

        try {
            SSLContext sc = SSLContext.getInstance("TLS");
            sc.init(null, new TrustManager[]{new TrustAllCerts()}, new SecureRandom());

            ssfFactory = sc.getSocketFactory();
        } catch (Exception e) {
        }

        return ssfFactory;
    }

    private static class TrustAllCerts implements X509TrustManager {
        public void checkClientTrusted(X509Certificate[] chain, String authType) throws CertificateException {
        }

        public void checkServerTrusted(X509Certificate[] chain, String authType) throws CertificateException {
        }

        public X509Certificate[] getAcceptedIssuers() {
            return new X509Certificate[0];
        }
    }

}

3、另外，本文还提供一个代理服务器的写法，支持文件上传等功能

@Controller
public class ProxyController{

    // 内网服务器地址+端口
    private String targetAddr = "https://www.baidu.com/";
    private String proxyaAddr = "http://10.0.0.100:9000";


    /**
     * 代理所有请求
     *
     * @param request
     * @param response
     * @throws Exception
     */
    @RequestMapping(value = "/proxy/**", method= RequestMethod.POST)
    public void proxy(HttpServletRequest request, HttpServletResponse response) throws IOException, URISyntaxException {
        // String url = URLDecoder.decode(request.getRequestURL().toString(), "UTF-8");
        URI uri = new URI(request.getRequestURI());
        String path = uri.getPath();
        String query = request.getQueryString();
        String target = targetAddr + path.replace("/proxy", "");
        if (query != null && !query.equals("") && !query.equals("null")) {
            target = target + "?" + query;
        }
        URI newUri = new URI(target);
        // 执行代理查询
        String methodName = request.getMethod();

        HttpMethod httpMethod = HttpMethod.resolve(methodName);
        if (httpMethod == null) {
            return;
        }
        InputStream stream = null;
        String contentType = request.getContentType();

        // 兼容文件上传的请求
        if (contentType != null && contentType.startsWith("multipart/form-data")){
            MultipartHttpServletRequest mulReq = (MultipartHttpServletRequest) request;
            Map<String, MultipartFile> map = mulReq.getFileMap();
            List<MultipartFile> valueList = new ArrayList<MultipartFile>(map.values());
            MultiValueMap<String, Object> params = new LinkedMultiValueMap();
            for (MultipartFile file : valueList) {
                File newFile = File.createTempFile("temp",file.getOriginalFilename());
                FileUtils.copyInputStreamToFile(file.getInputStream(), newFile);
                FileSystemResource resource = new FileSystemResource(newFile);
                params.add(file.getName(), resource);

            }
            RestTemplate restTemplate = new RestTemplate();

            // 设置请求头
            HttpHeaders headers = new HttpHeaders();
            Enumeration<String> headerNames = request.getHeaderNames();
            while (headerNames.hasMoreElements()) {
                String headerName = headerNames.nextElement();
                System.out.println(headerName + ":" + request.getHeader(headerName));
                headers.set(headerName,request.getHeader(headerName));
            }

            // 手动设置请求头的token信息
            headers.set("Authorization",request.getHeader("Authorization"));

            // 用HttpEntity封装整个请求报文
            HttpEntity<MultiValueMap<String, Object>> files = new HttpEntity<MultiValueMap<String, Object>>(params,headers);

            String res = restTemplate.postForEntity(target, files, String.class).getBody();
            InputStream is =new ByteArrayInputStream(res.getBytes("UTF-8"));
            stream = is;
            // 其他请求例如get post put delete都可使用
        }else {
            ClientHttpRequest delegate = new SimpleClientHttpRequestFactory().createRequest(newUri, httpMethod);
            Enumeration<String> headerNames = request.getHeaderNames();
            // 设置请求头
            while (headerNames.hasMoreElements()) {
                String headerName = headerNames.nextElement();
                Enumeration<String> v = request.getHeaders(headerName);
                List<String> arr = new ArrayList<>();
                while (v.hasMoreElements()) {
                    arr.add(v.nextElement());
                }
                delegate.getHeaders().addAll(headerName, arr);
            }
            StreamUtils.copy(request.getInputStream(), delegate.getBody());
            // 执行远程调用
            ClientHttpResponse clientHttpResponse = delegate.execute();
            response.setStatus(clientHttpResponse.getStatusCode().value());

            // 设置响应头
            clientHttpResponse.getHeaders().forEach((key, value) -> value.forEach(it -> {
                response.setHeader(key, it);
            }));
            stream = clientHttpResponse.getBody();
        }

        // 将获取到的输入流再次输出到页面输出流中
        StreamUtils.copy(stream, response.getOutputStream());
    }
}