Openlayers WFS基于java与C#的跨域代理

原文地址:http://blog.csdn.net/freeland1/article/details/41204485

通常web项目于gis服务器不在同一域下，这就涉及到了wfs跨域问题。

一 几种常见的wfs跨域比较：

1.1 基于openlayers自带的proxy.cgi

缺陷：正常可以，但部署麻烦，要装python，还要配置iis，tomcat。。。并且在wfs参数中，比如viewparam中有',\字符的话，cgi的python代理会报错。

1.2 基于esri的proxy

缺陷：在浏览器输入wfs请求可以通过，但是在程序里请求wfs参数，一般url会被自动转码，然后代理识别不了，一模一样的转码后就可以通过。个人猜测esri代理的转码部分没有通用解析。有高人可指导。

1.3 使用后台自定义代理

1.3.1 使用ashx

 using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Web;
 using System.Net;
 using System.IO;

 namespace WebApplication1
 {
     /// <summary>
     /// OpenlayerProxy 的摘要说明
     /// </summary>
     public class OpenlayerProxy : IHttpHandler
     {
         public void ProcessRequest(HttpContext context)
         {
             if (string.IsNullOrEmpty(context.Request["URL"])) return;
             HttpWebRequest request = (HttpWebRequest)WebRequest.Create(context.Request["URL"]);
             request.UserAgent = context.Request.UserAgent;
             request.ContentType = context.Request.ContentType;
             request.Method = context.Request.HttpMethod;

             byte[] trans = new byte[1024];
             int offset = 0;
             int offcnt = 0;

             if (request.Method.ToUpper() == "POST")
             {
                 Stream nstream = request.GetRequestStream();
                 while (offset < context.Request.ContentLength)
                 {
                     offcnt = context.Request.InputStream.Read(trans, offset, 1024);
                     if (offcnt > 0)
                     {
                         nstream.Write(trans, 0, offcnt);
                         offset += offcnt;
                     }
                 }
                 nstream.Close();
             }
             HttpWebResponse response = (HttpWebResponse)request.GetResponse();
             //Encoding enc = Encoding.GetEncoding(65001);
             context.Response.ContentType = response.ContentType;
             StreamReader loResponseStream = new StreamReader(response.GetResponseStream());
             string lcHtml = loResponseStream.ReadToEnd();
             context.Response.Write(lcHtml);
             response.Close();
             loResponseStream.Close();

         }

         public bool IsReusable
         {
             get
             {
                 return false;
             }
         }

     }
 }

1.3.2 基于java的servlet

 package com.nkstar.action;

 import javax.servlet.http.HttpServlet;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
 import java.net.HttpURLConnection;
 import java.net.URL;

 import javax.servlet.ServletException;
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;

 /**
  * This is a transparent HTTP proxy written in Java that is similar to the proxy
  * in the OpenLayers examples, which is written in Python. These proxies are
  * used to circumvent browser restrictions on cross-domain requests with
  * Javascript.
  * </p>
  * <p>
  * To use the proxy you need to 1) configure the proxy servlet in your web.xml
  * and 2) use OpenLayers.setProxyHost to set the url-path to the proxy. If the
  * proxy is configured to listen to the url-pattern '/gwtOpenLayersProxy/*' then
  * the proxy host should be set to 'gwtOpenLayersProxy?targetURL='.
  * </p>
  * Initial code for this proxy is based upon <a href=
  * "http://trac.openlayers.org/changeset/8099/sandbox?format=diff&new=8099">the
  * following code</a><br />
  * see also <a href=
  * "http://java.sun.com/docs/books/tutorial/networking/urls/readingWriting.html"
  * title="this networking tutorial">this networking tutorial</a>
  * <p>
  */
 @SuppressWarnings("serial")
 public class OpenLayersProxyServlet extends HttpServlet {

     protected void doGet(HttpServletRequest request,
             HttpServletResponse response) throws ServletException, IOException {
         processRequest(request, response);
     }

     protected void doPost(HttpServletRequest request,
             HttpServletResponse response) throws ServletException, IOException {
         processRequest(request, response);
     }

     private void processRequest(HttpServletRequest request,
             HttpServletResponse response) throws ServletException, IOException {

         HttpURLConnection connection = null;
         InputStream istream = null; // input to proxy
         OutputStream ostream = null; // output from proxy
         InputStream connectionIstream = null; // output for the target is
         // input for the connection
         OutputStream connectionOstream = null; // input for the target is
         // output for the connection

         String remoteHost = request.getRemoteHost(); // get host address of
         // client - for checking
         // allowedHosts
         boolean allowedHost = isAllowedHost(remoteHost); // The allowedHosts
         // are the hosts
         // that are allowed
         // to use the Open
         // Proxy.
         try {
             // easy way to ignore case of param?
             if (request.getParameter("targetURL") != null
                     && request.getParameter("targetURL") != "" && allowedHost) {

                 // HTTPUrlConnection looks at http.proxyHost and http.proxyPort
                 // system properties.
                 // Make sure these properties are set these if you are behind a
                 // proxy.

                 // step 1: initialize
                 String requestMethod = request.getMethod();

                 URL targetURL = new URL(request.getParameter("targetURL"));
                 connection = (HttpURLConnection) targetURL.openConnection();
                 connection.setRequestMethod(requestMethod);
                 transferHTTPRequestHeaders(connection, request);

                 // step 2: proxy requests
                 if (requestMethod.equals("GET")) {
                     // default for setDoInput is true
                     connectionIstream = connection.getInputStream();
                 }
                 ;
                 if (requestMethod.equals("POST")) {
                     transferHTTPRequestHeadersForPOST(connection, request);
                     int clength = request.getContentLength();// clength is
                     // for checking
                     // if there is a
                     // POST body. Is
                     // that
                     // sufficient?

                     if (clength > 0) {
                         istream = request.getInputStream();
                         connection.setDoOutput(true);// for POST we need to
                         // write to connection
                         connection.setRequestProperty("Content-Length", Integer
                                 .toString(clength)); // only valid for POST
                         // request
                         connectionOstream = connection.getOutputStream();
                         // copy the request body to remote outputStream
                         copy(istream, connectionOstream);
                     }
                     connectionIstream = connection.getInputStream();
                 }

                 // step 3: return output
                 // can output be the same for GET/POST? or different return
                 // headers?
                 // servlet may return 3 things: status code, response headers,
                 // response body
                 // status code and headers have to be set before response body
                 response.setContentType(connection.getContentType());
                 ostream = response.getOutputStream();
                 copy(connectionIstream, ostream);
             }
             // if not targetURL send page that targetURL is required param
         } catch (Exception e) {
             response.setStatus(500); // what will user get? default page for
             // response code
             // WMS/WFS have specific responses to errors
             // response.getWriter();//will writing custom result help
             e.printStackTrace();
         } finally {
             if (istream != null) {
                 istream.close();
             }
             if (ostream != null) {
                 ostream.close();
             }
             if (connectionIstream != null) {
                 connectionIstream.close();
             }
             if (connectionOstream != null) {
                 connectionOstream.close();
             }
         }

     }

     private void copy(InputStream istream, OutputStream ostream)
             throws Exception {
         int bufferSize = 4 * 4 * 1024;// same buffer size as in Jetty utils
         // (2*8192)
         byte[] buffer = new byte[bufferSize];
         int read;
         while ((read = istream.read(buffer)) != -1) {
             ostream.write(buffer, 0, read);
         }
     }

     private void transferHTTPRequestHeaders(HttpURLConnection connection,
             HttpServletRequest request) {
         // TODO make sure all headers are copied to target, see for HTTP headers
         // http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html
         // Do request.getProperties to get request properties
         if (request.getHeader("Accept") != null) {
             connection
                     .setRequestProperty("Accept", request.getHeader("Accept"));
         }
         if (request.getHeader("Accept-Charset") != null) {
             connection.setRequestProperty("Accept-Charset", request
                     .getHeader("Accept-Charset"));
         }
         if (request.getHeader("Accept-Encoding") != null) {
             // TODO browsers accept gzipped, should proxy accept gzip and how to
             // handle it?
             // connection.setRequestProperty("Accept-Encoding",
             // request.getHeader("Accept-Encoding"));
         }
         if (request.getHeader("Authorization") != null) {
             connection.setRequestProperty("Authorization", request
                     .getHeader("Authorization"));
         }
         if (request.getHeader("Connection") != null) {
             // TODO HTTP/1.1 proxies MUST parse the Connection header field
             // before a message is forwarded and, for each connection-token in
             // this field, remove any header field(s) from the message with the
             // same name as the connection-token.
             // connection.setRequestProperty("Connection",
             // request.getHeader("Connection"));
         }

         // set de-facto standard proxy headers (x-forwarded-for, others?s)
         if (request.getHeader("X-Forwarded-For") != null) {
             connection.setRequestProperty("X-Forwarded-For", request
                     .getHeader("X-Forwarded-For"));// TODO append IP proxy
         } else {
             connection.setRequestProperty("X-Forwarded-For", request
                     .getRemoteAddr());// TODO append IP proxy
         }
     }

     private void transferHTTPRequestHeadersForPOST(
             HttpURLConnection connection, HttpServletRequest request) {
         if (request.getHeader("Content-Type") != null) {
             connection.setRequestProperty("Content-Type", request
                     .getContentType());
         } else {
             // throw exception?
         }
     }

     private boolean isAllowedHost(String remoteHost) {
         // TODO checking of host
         return true;
     }

 }

后两种都避免了一和二的缺陷，通用可行，直接可以放在web项目当中部署，简单操作。

使用说明

OpenLayer2代理使用，只需在程序开头或init方法第一句写上proxyhost即可。

 OpenLayers.ProxyHost = '/OpenlayerProxy.ashx?URL=';

   var url = 'http://localhost:8090/geoserver/wfs?SERVICE=WFS&VERSION=1.1.0&REQUEST=GetFeature&OUTPUTFORMAT=GML2&TYPENAME=pgrouting:Mypgrouting&viewparams=' + viewparams;
         var request = OpenLayers.Request.POST({
             url: url,
             callback: onComplete
         });

OpenLayer3 代理使用

 queryButton.addEventListener('click', function (event) {
        var viewparams = "ARRAY[[" + locatearr.join("],[") + "]]";
        viewparams = stringReg(viewparams);
        viewparams = "destinationarr:" + viewparams;
        var url ='http://localhost:8090/geoserver/wfs?SERVICE=WFS&VERSION=1.1.0&REQUEST=GetFeature&OUTPUTFORMAT=json&TYPENAME=pgrouting:Mypgrouting&viewparams=' + viewparams;
        url = '/OpenlayerProxy.ashx?URL=' + encodeURIComponent(url);
        $.ajax({
            type: "POST",
            url: url,
            dataType:"text",
            success: onComplete
        });
    });

需要对url进行编码，否则代理进去丢失参数。