Response Header Download
Monthly Archives: February 2013
Servlet that Generate JPEG Images
Servlet that Generate JPEG Images
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.*;
import javax.imageio.ImageIO;
import javax.servlet.*;
import javax.servlet.http.*;
public class ImageDevelop extends HttpServlet
{
protected void processRequest(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException
{
response.setContentType("image/jpeg");
OutputStream out=response.getOutputStream();
try
{
BufferedImage image=new BufferedImage(200,200,BufferedImage.TYPE_INT_RGB);
Graphics2D g=(Graphics2D)image.getGraphics();
g.setBackground(new Color(999));
g.drawString("Test",50,50);
g.drawLine(30, 30, 30, 150);
g.drawLine(30,150, 150, 150);
g.drawLine(150, 150, 150, 30);
g.drawLine(150, 30, 30, 30);
ImageIO.write(image, "jpg", out);
} finally {
out.close();
}
}
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);
}
}
Example of Refresh Response Header
Example of refresh header
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class Refresh extends HttpServlet
{
static int i;
static
{
int i=0;
}
protected void processRequest(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException
{
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
try {
response.setHeader("Refresh", "1");
//or
//response.setIntHeader("Refresh", 1);
out.print("<h1>Value Of i : " + i + "<h1>");
i++;
} finally {
out.close();
}
}
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);
}
}
Servlet Practical Assignment -2
Servlet Practical Assignment -2
1) Develop a Servlet which will display different images based on the name of the html file.
2) Write a servlet that builds an Excel spreadsheet that display student name,mark1, mark2, mark3 and sum of three subjects mark.
3) Suppose we have three pdf files for the MCA-1 result, MCA-2 result and MCA-3 result respectively. Now write a Servlet which displays the appropriate PDF file to the client, by looking at a request parameter for the year (1, 2 or 3). (use response.sendRedirect() method )
4) Write a Servlet to show special welcome message for users who are not accessing Internet Explorer.
5) Write a Servlet to show special message when user comes from google, yahoo and MSN Search engine.
6) Write a servlet that returns a “page not found” error page (404) unless the user supplies a favourite Language request (form) parameter with a value of “Java.”
Example of User-Agent request header
WrongDestination.java
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
/** Servlet that sends IE users to the Netscape home page and
* Netscape (and all other) users to the Microsoft home page.
*/
public class WrongDestination extends HttpServlet
{
public void doGet(HttpServletRequest request,HttpServletResponse response)
throws ServletException, IOException
{
String userAgent = request.getHeader("User-Agent");
if ((userAgent != null) && (userAgent.indexOf("MSIE") != -1))
{
response.sendRedirect("http://home.netscape.com");
}
else
{
response.sendRedirect("http://www.microsoft.com");
}
}
}
Example of sendError() method of HttpServletResponse interface
sendErrorEx.java
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class sendErrorEx extends HttpServlet
{
public void doGet(HttpServletRequest req, HttpServletResponse res)
throws ServletException,IOException
{
res.setContentType("text/html");
PrintWriter out = res.getWriter();
out.println("This won't be seen if sendError() is called");
if (req.getParameter("param") == null) {
// res.sendError(res.SC_BAD_REQUEST, "param needed"); OR
res.sendError(401, "param needed");
}
}
}
First time run these program with these URL:
http://localhost:8080/sendErrorEx?param=abc
Second time run these program with these URL:
http://localhost:8080/sendErrorEx
Second time it gives you error message when you do not pass the param parameter.
Servlet program that shows all standard CGI variables
ShowCGIVariables.java
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.util.*;
/** Creates a table showing the current value of each
* of the standard CGI variables.
*/
public class ShowCGIVariables extends HttpServlet
{
public void doGet(HttpServletRequest request,HttpServletResponse response)
throws ServletException, IOException
{
response.setContentType("text/html");
PrintWriter out = response.getWriter();
String[][] variables =
{ { "AUTH_TYPE", request.getAuthType() },
{ "CONTENT_LENGTH",
String.valueOf(request.getContentLength()) },
{ "CONTENT_TYPE", request.getContentType() },
{ "DOCUMENT_ROOT",
getServletContext().getRealPath("/") },
{ "PATH_INFO", request.getPathInfo() },
{ "PATH_TRANSLATED", request.getPathTranslated() },
{ "QUERY_STRING", request.getQueryString() },
{ "REMOTE_ADDR", request.getRemoteAddr() },
{ "REMOTE_HOST", request.getRemoteHost() },
{ "REMOTE_USER", request.getRemoteUser() },
{ "REQUEST_METHOD", request.getMethod() },
{ "SCRIPT_NAME", request.getServletPath() },
{ "SERVER_NAME", request.getServerName() },
{ "SERVER_PORT",
String.valueOf(request.getServerPort()) },
{ "SERVER_PROTOCOL", request.getProtocol() },
{ "SERVER_SOFTWARE",
getServletContext().getServerInfo() }
};
String title = "Servlet Example: Showing CGI Variables";
String docType =
"<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.0 " +
"Transitional//EN\">\n";
out.println(docType +
"<HTML>\n" +
"<HEAD><TITLE>" + title + "</TITLE></HEAD>\n" +
"<BODY BGCOLOR=\"#FDF5E6\">\n" +
"<CENTER>\n" +
"<H1>" + title + "</H1>\n" +
"<TABLE BORDER=1>\n" +
" <TR BGCOLOR=\"#FFAD00\">\n" +
" <TH>CGI Variable Name<TH>Value");
for(int i=0; i<variables.length; i++)
{
String varName = variables[i][0];
String varValue = variables[i][1];
if (varValue == null)
varValue = "<I>Not specified</I>";
out.println(" <TR><TD>" + varName + "<TD>" + varValue);
}
out.println("</TABLE></CENTER></BODY></HTML>");
}
/** POST and GET requests handled identically. */
public void doPost(HttpServletRequest request,HttpServletResponse response)
throws ServletException, IOException
{
doGet(request, response);
}
}
Example of Referer Request Header
jrun-powered.jpg,resin-powered.jpg and tomcat-power.gif images are required in folder c:/tomcat/webapps/ROOT/images/jrun-powered.jpg to run this example.
CustomizeImage.java
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
/** Servlet that displays referer-specific image. */
public class CustomizeImage extends HttpServlet
{
public void doGet(HttpServletRequest request,HttpServletResponse response)
throws ServletException, IOException
{
response.setContentType("text/html");
PrintWriter out = response.getWriter();
String referer = request.getHeader("Referer");
if (referer == null)
{
referer = "<I>none</I>";
}
String title = "Referring page: " + referer;
String imageName;
if (contains(referer, "JRun"))
{
imageName = "jrun-powered.jpg";
} else if (contains(referer, "Resin"))
{
imageName = "resin-powered.jpg";
} else
{
imageName = "tomcat-power.gif";
}
String imagePath = "../images/" + imageName;
out.println( "<HTML>\n" +
"<HEAD><TITLE>" + title + "</TITLE></HEAD>\n" +
"<BODY BGCOLOR=\"#FDF5E6\">\n" +
"<CENTER><H2>" + title + "</H2>\n" +
"<IMG SRC=\"" + imagePath + "\">\n" +
"</CENTER></BODY></HTML>");
}
private boolean contains(String mainString,String subString)
{
return(mainString.indexOf(subString) != -1);
}
}
Tomcat-Referer.html,JRun-Referer.html and Resin-Referer.html
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD><TITLE>Referer Test</TITLE></HEAD> <BODY BGCOLOR="#FDF5E6"> <H1 ALIGN="CENTER">Referer Test</H1> Click <A HREF="CustomizeImage">here</A> to visit the servlet. </BODY></HTML>
Example of MIME type
ApplesAndOranges.java
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class ApplesAndOranges extends HttpServlet {
public void doGet(HttpServletRequest request,HttpServletResponse response)
throws ServletException, IOException
{
response.setContentType("application/vnd.ms-excel");
PrintWriter out = response.getWriter();
out.println("\tQ1\tQ2\tQ3\tQ4\tTotal");
out.println("Apples\t78\t87\t92\t29\t=SUM(B2:E2)");
out.println("Oranges\t77\t86\t93\t30\t=SUM(B3:E3)");
}
}
Web Technology & Application Development – 2640002 