📄 checkname.java
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/******************************************************************************************************************
IT03July Java Assignment
Message Board!
Created by Jason(632)
This program using JDBC to record user detail and using HTTP session to remember user infomations from HTML pages.
******************************************************************************************************************/
package myelf;
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.sql.*;
import java.util.*;
import java.text.*;
public class checkname extends HttpServlet
{
public void doPost (HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException
{
String url = "jdbc:hsqldb:" + getServletContext().getRealPath("/db/myDB");
Statement statement;
ResultSet resultSet;
Connection connection;
HttpSession session;
session = request.getSession();//start to geting user infomation into session
String username = request.getParameter ("user");
String password = request.getParameter ("pass");
try
{
Class.forName ("org.hsqldb.jdbcDriver");
connection = DriverManager.getConnection (url,"sa", "");
}
catch (ClassNotFoundException cnfex)
{
ErrorMessage (response, "Failed to load JDBC/ODBC driver.");
return;
}
catch (SQLException sqlex)
{
ErrorMessage (response, "Unable to connect to database.");
return;
}
try
{
statement = connection.createStatement ();
resultSet = statement.executeQuery ("SELECT * FROM Message;");
String number = getMessage(resultSet);
resultSet = statement.executeQuery ("SELECT * FROM User;");
String member = getMessage(resultSet);
resultSet = statement.executeQuery ("SELECT * FROM User WHERE Username = '" + username + "' AND Password = '" + password + "';"); //check the user and password in the database using SQl statement
checkInvalid(response, resultSet, member, number);
statement.close ();
session.putValue("username", username);
}
catch (SQLException sqlex)
{
String message = sqlex.getMessage();
ErrorMessage ( response, message );
return;
}
try
{
connection.close ();
}
catch (SQLException sqlex)
{
}
}
public void ErrorMessage (HttpServletResponse response,String message) //Error message
throws ServletException, IOException
{
PrintWriter output;//start to write HTML files in java
response.setContentType ("text/html");
output = response.getWriter ();
output.println ("<HTML><HEAD><TITLE>Error</TITLE></HEAD><BODY>");
output.println ("<H1>" + message + "</H1></BODY></HTML>");
output.println("<a href = javascript:history.back()>BACK</a>");
output.close ();
}
private void checkInvalid (HttpServletResponse response,ResultSet rs, String member, String number)//welcome page
throws ServletException, IOException, SQLException
{
boolean moreRecords;
PrintWriter output;//start to write HTML files in java
response.setContentType ("text/html");
output = response.getWriter ();
moreRecords = rs.next ();
output.println("<html>");
output.println("<head>");
output.println("<meta http-equiv=\"Content-Type\" content=\"text/html; charset=gb2312\">");
output.println("<title>Welcome!</title>");
output.println("<style type=\"text/css\">");
output.println("<!--");
output.println("body {");
output.println("background-color: #66CCFF;");
output.println("margin-left: 10px;");
output.println("margin-top: 10px;");
output.println("margin-right: 10px;");
output.println("margin-bottom: 10px;");
output.println("}");
output.println(".style7 {font-family: Tahoma}");
output.println("body,td,th {");
output.println("font-family: Tahoma;");
output.println("}");
output.println("-->");
output.println("</style></head>");
output.println("");
output.println("<body>");
if (!moreRecords)
{
output.println("<table width=\"745\" border=\"0\" align=\"center\" cellpadding=\"0\" cellspacing=\"0\">");
output.println("<tr>");
output.println("<th width=\"139\" scope=\"col\"><img src=\"http://myjavaserver.com/~myelf/pic/logo.jpg\" width=\"139\" height=\"82\"></th>");
output.println("<th width=\"318\" class=\"style7\" scope=\"col\"> </th>");
output.println("<th width=\"45\" scope=\"col\"> </th>");
output.println("<th width=\"59\" valign=\"baseline\" scope=\"col\"></span></th>");
output.println("<th width=\"103\" valign=\"baseline\" scope=\"col\"></th>");
output.println("<th width=\"81\" valign=\"baseline\" scope=\"col\"></th>");
output.println("</tr>");
output.println("</table>");
output.println("<table width=\"746\" height=\"65\" border=\"0\" align=\"center\" cellpadding=\"0\" cellspacing=\"0\">");
output.println("<tr>");
output.println("<th scope=\"col\"> </th>");
output.println("</tr>");
output.println("<tr>");
output.println("<th scope=\"col\"> </th>");
output.println("</tr>");
output.println("<tr>");
output.println("<th scope=\"col\"> </th>");
output.println("</tr>");
output.println("<tr>");
output.println("<th scope=\"col\"> </th>");
output.println("</tr>");
output.println("<tr>");
output.println("<th scope=\"col\"><div align=\"left\">Sorry, the password you had enter is incorrect. Click <a href= javascript:history.back() ><em>Here</em></a> back to the login page! </div></th>");
output.println("</tr>");
output.println("<tr>");
output.println("<th scope=\"col\"><div align=\"left\">Didn't have a permission to enter? Click <a href=\"http://myjavaserver.com/~myelf/register.htm\"><em>Here</em></a> to register a valid username! </div></th>");
output.println("</tr>");
output.println("</table>");
output.println("<p> </p>");
output.println("<p> </p>");
output.println("<p> </p>");
output.println("<p> </p>");
output.close ();
}
else
{
String name =rs.getString("Username");
output.println("<form name=\"form\" method=\"post\" action=\"http://www.myjavaserver.com/servlet/myelf.message\">");
output.println("<table width=\"745\" border=\"0\" align=\"center\" cellpadding=\"0\" cellspacing=\"0\">");
output.println("<tr>");
output.println("<th width=\"139\" scope=\"col\"><img src=\"http://myjavaserver.com/~myelf/pic/logo.jpg\" width=\"139\" height=\"82\"></th>");
output.println("<th width=\"318\" class=\"style7\" scope=\"col\"> </th>");
output.println("<th width=\"45\" scope=\"col\"> </th>");
output.println("<th width=\"59\" valign=\"baseline\" scope=\"col\"></span></th>");
output.println("<th width=\"103\" valign=\"baseline\" scope=\"col\"></span></th>");
output.println("<th width=\"81\" valign=\"baseline\" scope=\"col\"></span></th>");
output.println("</tr>");
output.println("</table>");
output.println("<table width=\"746\" height=\"65\" border=\"0\" align=\"center\" cellpadding=\"0\" cellspacing=\"0\">");
output.println("<tr>");
output.println("<th scope=\"col\"> </th>");
output.println("</tr>");
output.println("<tr>");
output.println("<th scope=\"col\"> </th>");
output.println("</tr>");
output.println("<tr>");
output.println("<th scope=\"col\"><h3>Welcome to Jason's Message Board! </h3></th>");
output.println("</tr>");
output.println("<tr>");
output.println("<th scope=\"col\"> </th>");
output.println("</tr>");
output.println("<tr>");
output.println("<th scope=\"col\"><div align=\"left\">Welcome back, <font color = \"green\" >" + name + "</font> ! </div></th>");
output.println("</tr>");
output.println("<tr>");
output.println("<th scope=\"col\"><div align=\"left\">There are <font color = \"red\">" + member + "</font> register member(s) and <font color = \"red\">" + number + "</font> message(s) in the message board! </div></th>");
output.println("</tr>");
output.println("<tr>");
output.println("<th scope=\"col\"><div align=\"left\"></div></th>");
output.println("</tr>");
output.println("<tr>");
output.println("<th scope=\"col\"><input name=\"Submit\" type=\"submit\" class=\"style7\" value=\"GO TO THE MESSAGE BOARD\"></th>");
output.println("</tr>");
output.println("</table>");
output.println("<p> </p>");
output.println("<p> ");
output.println("</form>");
output.close ();
}
output.println("</body>");
output.println("</html>");
output.close ();
}
private String getMessage (ResultSet rs) //get the total user and message in the database
throws SQLException
{
int number = 0;
String messageNumber;
boolean moreRecords;
moreRecords = rs.next ();
while (moreRecords)
{
number++;
moreRecords = rs.next ();
}
messageNumber = ""+number;
return messageNumber;
}
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