Java/Servlets/Response

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

 
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");
  }
}

Get output stream from HttpServletResponse

  
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();
  }
}

Set content type to charset=ISO-8850-1

  
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();
  }
}

URL rewriting through HttpServletResponse

  
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 <b>" + session.getId());
    out.println("</b> and you have hit this page <b>" + count
        + "</b> 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();
  }
}