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I am designing an attendance system. on the attendance page, there is roll no., name and present (which is a checkbox). Now what I want to do is if the checkbox is checked it will update attended and total field in my attendance table. and if it is unchecked then it will only update the total field.
I am facing a problem when it is unchecked otherwise it is updating in the table.

att.jsp

<FORM method="POST" ACTION="test1.jsp">
 <table>
 <% for(int i=0;i<results.size();i++)%>
 <tr>
 <td>
 <%=results.get(i)%>
 </td>
 <td>
 <%=name1.get(i)%>
 </td>
 <td>
 <input TYPE=checkbox name=sports VALUE=<%=results.get(i)%>>
 </td>
 <td>
 Present
 </td>

 </tr>

 <% %>

 </table>
 <br> <INPUT TYPE=submit name=submit Value="Submit">
</FORM>

test1.jsp

 <%! String[] sports; %>
 <% 
 Class.forName("com.mysql.jdbc.Driver");
 Connection con = 
 DriverManager.getConnection("jdbc:mysql://localhost:3306/sis","root","");
 Statement st=con.createStatement();

 sports = request.getParameterValues("sports");
 for (int i = 0; i < sports.length; i++) 
 
 //out.println(sports[i]);
 
 //if (sports != null) 
 //{
 for (int i = 0; i < sports.length; i++) 
 
 if (sports[i] != null) 
 
 //out.println ("<b> NOT"+sports[i]+"<b>");

 st.executeUpdate("update attendancetb set attended = attended+1, total 
 = total+1 where SID in ('"+sports[i]+"')");
 

 
 %>

You have to pass the list of all sports (results from the att.jsp) to the test1.jsp as the session attribute, and then iterate over all sports, and use different update statements for the checked case and the unchecked case.

Side notes:

1. Never EVER use string concatenation to create SQL commands from user input, not even in a school project. This makes your code vulnerable to SQL Injection. Use PreparedStatement instead.




2. Do not use scriptlets (<% ... %>), use JSTL.




3. Do not put business logic and/or SQL code into JSP, use Model-View-Controller architecture.