Re: how do i insert into data base

Stanimir Stamenkov wrote:
>> I haven't exactly got what problem you're having.  You insert into
>> an SQL database using an INSERT statement.  You would get the info
>> to insert making the user post back the form he has filled to the
>> server.

mak wrote:
> There is two procedure.
> 1st a user selects the subject, month, year. And clicks submit to get
> the student who has taken  that subject. Here in fornt of all the
> students roll no. a text box is comes in which user has to put the
> total no. of lecture he has attended in that subject.
> all this happns in the same form.
> 2nd after entering the required field(i.e text box.) user clicks on
> submit button...Now the textbox data should go in other table along
> with students Roll. no.
> 
> Now I'm not able to understand how should i insert the value in the
> 'attendance' table.

I'll attempt an answer, but be aware that I've been wrong before.  I'm
also 
cross-posting (again) in order to unify your threads.

Side note:
Your listings will only be usable if you don't over-indent them.  Use
spaces, 
not TABs, for Usenet indentation, and keep the indentation level to a
small 
number, two, three or four spaces (pick one).  Also, most times they
should be 
complete, yet short, and illustrative.
<http://www.physci.org/codes/sscce.html>

Now back to your code:
> [code]
>  String  str1  =  "select  roll_no  from  student  where  sem_id  = 
(select
>  sem_id  from  subject  where  course_id  ='bsc_it'  and  sub_id  =
>  '"+getsub1+"')";

You've already been warned upthread about plugging in values like
'getsub1' 
directly into SQL statements.  Google for "SQL injection attack" for more
details.

>    ResultSet  rs    =  stmt.executeQuery(str1);
>  %>

One way to control your logic better is to have the JSP submit its form to
a 
servlet, which servlet in turn will call full-fledged Java classes to do
its 
logic.  Search the Sun site for "Model 2 architecture" for some details on
this.

Best practices dictate having no raw Java code ("scriptlet") in a JSP. 
Use 
tag libraries, especially the JSP Standard Tag Library (JSTL), and the
Model 2 
architecture instead.
<http://java.sun.com/javaee/5/docs/tutorial/doc/bnakc.html>
<http://java.sun.com/developer/technicalArticles/javaserverpages/servlets_jsp/index.html>
<http://java.sun.com/blueprints/guidelines/designing_enterprise_applications_2e/web-tier/web-tier5.html>
(follow the links, too)

>  <table align="center"  width=""  cellpadding="0"  cellspacing="0"
>      border="1"  cellspacing="1"  cellpadding="1">
>    <tr>
>      <td><input  type="text" value="Total  Lecture"  readonly=""/></td>
>      <td><input  type="text"  name="total_att"  maxlength="2"></td>
>    </tr>
>    <tr>
>      <td><input  type="text"  value="Student  roll  no."  readonly=""
/></td>

Why is the 'readonly' attribute there?

>    </tr>
>  <% while(rs.next())
>     {
>  %>
>  <%
>       stu_roll  =  rs.getString("roll_no");
>  %>
>    <tr  bordercolor="#CC3366">
>      <td><% out.println(stu_roll);  %>

The newline will look like any old whitespace to the HTML renderer. 
Better is 
the tag <c:out> or the old-fashioned '<%= stu_roll %>'.  Also, side note,
Java 
convention is to name variables without underscores, except for
compile-time 
constants.  Use compound word with each word part capitalized except the 
first: 'stuRoll'.

>      </td>
>      <td> <input  type="text" name="att"  /> </td>

Is this the value you want to insert?

>  </tr>&nbsp;
>  
> <%
>    }
>  
>   con.close();
>  }
>  catch(SQLException  e)
>  {
>     out.println("Exception  in  SQL"  +  e);
>  }
> %>
>  [/code]

You really need the Model-View-Controller (MVC) architecture, of which
"Model 
2" is an example, to do this easily.

Create a controller servlet, let's call it
'com.lewscanon.servlet.Controller' 
for the sake of argument.  In your web.xml, map it to a reasonable URL,
let's 
say '/Controller' within your application.

   <form action="Controller" method="post">

In the Controller, you pass the input parameters to the business logic, in

this case the parameter named "att".

public class Controller extends HttpServlet
{
  ...
  protected void doPost( HttpServletRequest req, HttpServletResponse rsp )
     throws ServletException, IOException
  {
    String screen = req.getParameter( "screen" );
    String att = req.getParameter( "att" );
    // probably shouldn't hard-code "att"

    MyDao dao = new MyDao( connectionInfo );
    boolean success = dao.insertAtt( att );
    req.setAttribute( "success", Boolean.valueOf( success ));
    // this puts the result in the request so the next JSP can retrieve it

    String nextPg = lookupView( screen, success );
    // returns next JSP to view, depending on previous 'screen'
    // and on the 'success' of the business logic.
    // An enum is probably better than a boolean for 'success'

    RequestDispatcher rd = req.getRequestDispatcher( nextPg );
    rd.forward( req, rsp );
  }
  ...
}

Now your MyDao class's 'insertAtt()' method handles the messy database
logic. 
    You create or retrieve a connection there, instantiate a
PreparedStatement 
with an INSERT command, plug in the att value, execute, and Bob's your
uncle.

Obviously I've left out a ton of detail, such as error-checking, or how do
you 
build a map of valid next views based on previous screen and logic
outcome, or 
how you organize your business logic in a class hierarchy of logic
handlers 
with a common supertype.

--
Lew