這篇文章研究了C#的代理程序編寫方法，用C#請移步這裡：http://www.linuxidc.com/Linux/2014-01/95412.htm
今天抄兩個Java的實現備用，第一段代碼：
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);
}
}
}
下面是第二段代碼：
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;
}
}
沒有細看，僅供參考，貌似網上第二段用得多些。
