hi all when I run my servlet which contains a form and click submit I get the following error, i cannot find the error in my code but there is obviously one when otherwise when I click submit the following error should not appear.
the sql should be when a user_id exists you can create a ‘lab’
The server encountered an internal error () that prevented it from fulfilling this request.
exception
java.lang.NumberFormatException: null
java.lang.Integer.parseInt(Unknown Source)
java.lang.Integer.parseInt(Unknown Source)
CreateLab.doPost(CreateLab.java:72)
javax.servlet.http.HttpServlet.service(HttpServlet.java:641)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class CreateLab
*/
@WebServlet("/CreateLab")
public class CreateLab extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public CreateLab() {
super();
// TODO Auto-generated constructor stub
}
int id;
int capacity;
String day = "";
String time = "";
String room = "";
int subject_id;
int user_id;
public void init() {
try {
Class.forName("com.mysql.jdbc.Driver");
Connection con =
DriverManager.getConnection("jdbc:mysql://localhost:3306/wae","root","");
System.out.println("JDBC driver loaded");
}
catch (ClassNotFoundException e) {
System.out.println(e.toString());
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
/**Process the HTTP Get request*/
public void doGet(HttpServletRequest request, HttpServletResponse response) throws
ServletException,IOException {
sendPageHeader(response);
sendRegistrationForm(request, response, false);
sendPageFooter(response);
}
/**Process the HTTP Post request*/
public void doPost(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
sendPageHeader(response);
capacity = Integer.parseInt(request.getParameter("capacity"));
id = Integer.parseInt(request.getParameter("id"));
day = request.getParameter("day");
time = request.getParameter("time");
room = request.getParameter("room");
user_id = Integer.parseInt(request.getParameter("user_id"));
subject_id = Integer.parseInt(request.getParameter("subject_id"));
boolean error = false;
String message = null;
try {
Class.forName("com.mysql.jdbc.Driver");
Connection con =
DriverManager.getConnection("jdbc:mysql://localhost:3306/wae","root","");
System.out.println("got connection");
System.out.println(id);
Statement s = con.createStatement();
String sql = "SELECT id FROM user" +
" WHERE id='" + user_id + "'";
ResultSet rs = s.executeQuery(sql);
if (rs.next()) {
rs.close();
sql = "INSERT INTO lab" +
" (capacity, day, time, room, subject_id, user_id)" +
" VALUES" +
" (" + capacity + "','" +
" '" + day + "'," +
" '" + time + "'," +
" '" + room + "','" + subject_id + "','" + user_id + "')";
System.out.println(sql);
int i = s.executeUpdate(sql);
if (i==1) {
message = "Successfully a new lab class.";
}
}
s.close();
con.close();
}
catch (SQLException e) {
message = "Error." + e.toString();
error = true;
}
catch (Exception e) {
message = "Error." + e.toString();
error = true;
}
if (message!=null) {
PrintWriter out = response.getWriter();
out.println("<B>" + message + "</B><BR>");
out.println("<HR><BR>");
}
if (error==true)
sendRegistrationForm(request, response, true);
else
sendRegistrationForm(request, response, false);
sendPageFooter(response);
}
/**
* Send the HTML page header, including the title
* and the <BODY> tag
*/
private void sendPageHeader(HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.println("<HTML>");
out.println("<HEAD>");
out.println("<TITLE>Create Lab Page</TITLE>");
out.println("</HEAD>");
out.println("<BODY>");
out.println("<CENTER>");
}
/**
* Send the HTML page footer, i.e. the </BODY>
* and the </HTML>
*/
private void sendPageFooter(HttpServletResponse response)
throws ServletException, IOException {
PrintWriter out = response.getWriter();
out.println("</CENTER>");
out.println("</BODY>");
out.println("</HTML>");
}
/**Send the form where the user can type in
* the details for a new user
*/
private void sendRegistrationForm(HttpServletRequest request,
HttpServletResponse response, boolean displayPreviousValues)
throws ServletException, IOException {
PrintWriter out = response.getWriter();
out.println("<BR><H2>Create A Lab</H2>");
out.println("<BR>Please enter the lab details.");
out.println("<BR>");
out.println("<BR><FORM METHOD=POST>");
out.println("<TABLE>");
out.println("<TR>");
out.println("<TD>Class Capacity</TD>");
out.print("<TD><INPUT TYPE=TEXT Name=capacity");
if (displayPreviousValues)
out.print(" VALUE=\"" + capacity + "\"");
out.println("></TD>");
out.println("</TR>");
out.println("<TR>");
out.println("<TD>Day</TD>");
out.print("<TD><INPUT TYPE=TEXT Name=day");
if (displayPreviousValues)
out.print(" VALUE=\"" + day + "\"");
out.println("></TD>");
out.println("</TR>");
out.println("<TR>");
out.println("<TD>Time</TD>");
out.print("<TD><INPUT TYPE=TEXT Name=time");
if (displayPreviousValues)
out.print(" VALUE=\"" + time + "\"");
out.println("></TD>");
out.println("</TR>");
out.println("<TR>");
out.println("<TD>Room</TD>");
out.print("<TD><INPUT TYPE=TEXT Name=room");
if (displayPreviousValues)
out.print(" VALUE=\"" + room + "\"");
out.println("></TD>");
out.println("</TR>");
out.println("<TR>");
out.println("<TD>subject_id</TD>");
out.print("<TD><INPUT TYPE=TEXT Name=subject_id");
if (displayPreviousValues)
out.print(" VALUE=\"" + subject_id + "\"");
out.println("></TD>");
out.println("</TR>");
out.println("<TR>");
out.println("<TD>user_id</TD>");
out.print("<TD><INPUT TYPE=TEXT Name=user_id");
out.println("></TD>");
out.println("</TR>");
if (displayPreviousValues)
out.print(" VALUE=\"" + user_id + "\"");
out.println("</TD>");
out.println("</TR>");
out.println("<TR>");
out.println("<TD><INPUT TYPE=RESET></TD>");
out.println("<TD><INPUT TYPE=SUBMIT></TD>");
out.println("</TR>");
out.println("</TABLE>");
out.println("</FORM>");
out.println("<BR>");
out.println("<BR>");
}
}
User this function each time you parse your string to int. getIntParameter returns 0 when parameter contains letters or null, otherwise it returns int vale.
In doPost function,
instead of