The example below shows how a servlet can determine both parameter names and values:
package coreservlets;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.util.*;
import coreservlets.ServletUtilities;
/** Shows all the parameters sent to the servlet via either
* GET or POST. Specially marks parameters that have
* no values or multiple values.
* <P>
* Taken from Core Servlets and JavaServer Pages
* from Prentice Hall and Sun Microsystems Press,
*
http://www.coreservlets.com/. * © 2000 Marty Hall; may be freely used or adapted.
*/
public class ShowParameters extends HttpServlet {
public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html");
PrintWriter out = response.getWriter();
String title = "Reading All Request Parameters";
out.println(ServletUtilities.headWithTitle(title) +
"<BODY BGCOLOR=\"#FDF5E6\">\n" +
"<H1 ALIGN=CENTER>" + title + "</H1>\n" +
"<TABLE BORDER=1 ALIGN=CENTER>\n" +
"<TR BGCOLOR=\"#FFAD00\">\n" +
"<TH>Parameter Name<TH>Parameter Value(s)");
Enumeration paramNames = request.getParameterNames();
while(paramNames.hasMoreElements()) {
String paramName = (String)paramNames.nextElement();
out.print("<TR><TD>" + paramName + "\n<TD>");
String[] paramValues =
request.getParameterValues(paramName);
if (paramValues.length == 1) {
String paramValue = paramValues[0];
if (paramValue.length() == 0)
out.println("<I>No Value</I>");
else
out.println(paramValue);
} else {
out.println("<UL>");
for(int i=0; i<paramValues.length; i++) {
out.println("<LI>" + paramValues[i]);
}
out.println("</UL>");
}
}
out.println("</TABLE>\n</BODY></HTML>");
}
public void doPost(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
Below shows how to access SESSION information:
package coreservlets;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.net.*;
import java.util.*;
/** Simple example of session tracking. See the shopping
* cart example for a more detailed one.
* <P>
* Taken from Core Servlets and JavaServer Pages
* from Prentice Hall and Sun Microsystems Press,
*
http://www.coreservlets.com/. * © 2000 Marty Hall; may be freely used or adapted.
*/
public class ShowSession extends HttpServlet {
public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html");
PrintWriter out = response.getWriter();
String title = "Session Tracking Example";
HttpSession session = request.getSession(true);
String heading;
// Use getAttribute instead of getValue in version 2.2.
Integer accessCount =
(Integer)session.getValue("accessCount");
if (accessCount == null) {
accessCount = new Integer(0);
heading = "Welcome, Newcomer";
} else {
heading = "Welcome Back";
accessCount = new Integer(accessCount.intValue() + 1);
}
// Use setAttribute instead of putValue in version 2.2.
session.putValue("accessCount", accessCount);
out.println(ServletUtilities.headWithTitle(title) +
"<BODY BGCOLOR=\"#FDF5E6\">\n" +
"<H1 ALIGN=\"CENTER\">" + heading + "</H1>\n" +
"<H2>Information on Your Session:</H2>\n" +
"<TABLE BORDER=1 ALIGN=\"CENTER\">\n" +
"<TR BGCOLOR=\"#FFAD00\">\n" +
" <TH>Info Type<TH>Value\n" +
"<TR>\n" +
" <TD>ID\n" +
" <TD>" + session.getId() + "\n" +
"<TR>\n" +
" <TD>Creation Time\n" +
" <TD>" +
new Date(session.getCreationTime()) + "\n" +
"<TR>\n" +
" <TD>Time of Last Access\n" +
" <TD>" +
new Date(session.getLastAccessedTime()) + "\n" +
"<TR>\n" +
" <TD>Number of Previous Accesses\n" +
" <TD>" + accessCount + "\n" +
"</TABLE>\n" +
"</BODY></HTML>");
}
/** Handle GET and POST requests identically. */
public void doPost(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
To create your own session variables, use session.setAttribute("name") method......and natch getAttribute("name") to access them.
