java实现Openlayers跨域代理程序

前段时间研究了C#的代理程序编写方法，用C#请移步这里：http://tedeum.iteye.com/blog/1883837

今天抄两个java的实现备用，第一段代码：

    package org.proxy.servlet;  
      
    import java.io.BufferedInputStream;  
    import java.io.BufferedReader;  
    import java.io.IOException;  
    import java.io.InputStreamReader;  
    import java.io.PrintWriter;  
    import java.net.URL;  
    import java.net.URLDecoder;  
      
    import javax.servlet.ServletException;  
    import javax.servlet.http.HttpServlet;  
    import javax.servlet.http.HttpServletRequest;  
    import javax.servlet.http.HttpServletResponse;  
      
    public class ProxyServlet extends HttpServlet {  
      
        /** 
         *  
         */  
        private static final long serialVersionUID = 4191419806910781940L;  
      
        @Override  
        protected void doGet(HttpServletRequest request, HttpServletResponse response)  
                throws ServletException, IOException {  
            String query = null;  
            response.setContentType("text/html;charset=UTF-8");  
            request.setCharacterEncoding("UTF-8");  
            query = request.getParameter("url");  
            System.out.println(query);  
            //query = "http://www.google.cn/search?hl=zh-CN&source=hp&q=proxy&btnG=Google+%E6%90%9C%E7%B4%A2&aq=f&oq=";  
            if (query == null) {  
                response.sendError(HttpServletResponse.SC_BAD_REQUEST, "Missing URL Parameter！");  
                return;  
            }  
            query = URLDecoder.decode(query);  
            PrintWriter out = response.getWriter();  
            int length = request.getContentLength();  
            byte[] bytes = new byte[length];  
            //System.out.println(length);  
            try{  
                URL url = new URL(query);  
                BufferedInputStream in = new BufferedInputStream(url.openStream());  
                System.out.println(in.read(bytes,0,length));  
                in.close();  
                out.print(bytes);  
                out.flush();  
                out.close();  
            }catch(IOException e){  
                response.sendError(HttpServletResponse.SC_NOT_FOUND, "Exception:"+e);  
                  
            }  
              
        }  
      
        @Override  
        protected void doPost(HttpServletRequest request, HttpServletResponse response)  
                throws ServletException, IOException {  
              
            String query = null;  
            response.setContentType("text/html;charset=UTF-8");  
            request.setCharacterEncoding("UTF-8");  
            query = request.getParameter("url");  
            System.out.println(query);  
            //query = "http://www.google.cn/search?hl=zh-CN&source=hp&q=proxy&btnG=Google+%E6%90%9C%E7%B4%A2&aq=f&oq=";  
            if (query == null) {  
                response.sendError(HttpServletResponse.SC_BAD_REQUEST, "Missing URL Parameter！");  
                return;  
            }  
            query = URLDecoder.decode(query);  
            PrintWriter out = response.getWriter();  
            int length = request.getContentLength();  
            byte[] bytes = new byte[length];  
            //System.out.println(length);  
            try{  
                URL url = new URL(query);  
                BufferedInputStream in = new BufferedInputStream(url.openStream());  
                System.out.println(in.read(bytes,0,length));  
                in.close();  
                out.print(bytes);  
                out.flush();  
                out.close();  
            }catch(IOException e){  
                response.sendError(HttpServletResponse.SC_NOT_FOUND, "Exception:"+e);  
                  
            }  
              
        }  
          
      
    }  

 下面是第二段代码：

package org.gwtopenmaps.openlayers.server;

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 GwtOpenLayersProxyServlet 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;
        }
}

 没有细看，仅供参考，貌似网上第二段用得多些。