Java/Servlets/Response

Add headers to prevent browsers and proxies from caching this reply.

   <source lang="java">

import javax.servlet.http.HttpServletResponse; /*

* Copyright 2005 Joe Walker
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
*     http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/

/**

* @author Joe Walker [joe at getahead dot ltd dot uk]
*/

public class Main {

 /**
  * Add headers to prevent browsers and proxies from caching this reply.
  * @param resp The response to add headers to
  */
 public static void addNoCacheHeaders(HttpServletResponse resp)
 {
     // Set standard HTTP/1.1 no-cache headers.
     resp.setHeader("Cache-Control", "no-store, no-cache, must-revalidate");
     // Set IE extended HTTP/1.1 no-cache headers (use addHeader).
     resp.addHeader("Cache-Control", "post-check=0, pre-check=0");
     // Set standard HTTP/1.0 no-cache header.
     resp.setHeader("Pragma", "no-cache");
     // Set to expire far in the past. Prevents caching at the proxy server
     resp.setHeader("Expires", "Sat, 6 May 1995 12:00:00 GMT");
 }

}

 </source>
   
  
 
  

Get output stream from HttpServletResponse

   <source lang="java">
 

import java.io.ByteArrayOutputStream; import java.io.DataInputStream; import java.io.DataOutputStream; import java.io.IOException; import javax.servlet.ServletException; import javax.servlet.ServletOutputStream; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; public class CounterServer extends HttpServlet {

 static final String COUNTER_KEY = "Counter.txt";
 public void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException,
     IOException {
   HttpSession session = req.getSession(true);
   int count = 1;
   Integer i = (Integer) session.getAttribute(COUNTER_KEY);
   if (i != null) {
     count = i.intValue() + 5;
   }
   session.setAttribute(COUNTER_KEY, new Integer(count));
   DataInputStream in = new DataInputStream(req.getInputStream());
   resp.setContentType("application/octet-stream");
   ByteArrayOutputStream byteOut = new ByteArrayOutputStream();
   DataOutputStream out = new DataOutputStream(byteOut);
   out.writeInt(count);
   out.flush();
   byte[] buf = byteOut.toByteArray();
   resp.setContentLength(buf.length);
   ServletOutputStream servletOut = resp.getOutputStream();
   servletOut.write(buf);
   servletOut.close();
 }

}

 </source>
   
  
 
  

Set content type to charset=ISO-8850-1

   <source lang="java">
 

import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class UnknownEncodingServlet extends HttpServlet {

 public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException,
     ServletException {
   response.setContentType("text/html; charset=ISO-8850-1");
   PrintWriter out = response.getWriter();
 }

}

 </source>
   
  
 
  

URL rewriting through HttpServletResponse

   <source lang="java">
 

import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; public class CounterRewrite extends HttpServlet {

 static final String COUNTER_KEY = "Counter.count";
 public void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException,
     IOException {
   HttpSession session = req.getSession(true);
   resp.setContentType("text/html");
   PrintWriter out = resp.getWriter();
   int count = 1;
   Integer i = (Integer) session.getAttribute(COUNTER_KEY);
   if (i != null) {
     count = i.intValue() + 1;
   }
   session.setAttribute(COUNTER_KEY, new Integer(count));
   out.println("<html>");
   out.println("<head>");
   out.println("<title>Session Counter</title>");
   out.println("</head>");
   out.println("<body>");
   out.println("Your session ID is " + session.getId());
   out.println(" and you have hit this page " + count
       + " time(s) during this browser session");
   String url = req.getRequestURI();
   out.println("<form method=GET action=\"" + resp.encodeURL(url) + "\">");
   out.println("<input type=submit " + "value=\"Hit page again\">");
   out.println("</form>");
   out.println("</body>");
   out.println("</html>");
   out.flush();
 }

}

 </source>