Passing a JSP variable from a resultset into a HTMl form

MPJH · Jul 22, 2003

Hi, I have a question regarding Resultsets in JSP.
I have a HTML form that gives 2 variables from textfields to another JSP page, which adds it to the database using the given variables in a query. Now i want the form to also include the messagenumber (this number is the primary key of the table messages). In the page I use a SQL statement (String query = "SELECT count(messageNr) FROM messages"; )to get the number of rows. In the receiving JSP page i then determine the new messageNumber by getting the value of the SQL statement and adding 1 to it.

The problem is that all of the elements work fine on their own. But when I use the Resultset to fill the HTML form it suddenly returns NULL. Here is the full source code and the error I get:

SOURCE:

<%@ page language="java" contentType="text/html" import="java.sql.*" %>

<html>
<head>
<title>** Add message **</title>
</head>
<body>
<body bgcolor="#000000" text="#FF0000" link="#FFFF00" vlink="#FFFF00" alink="#FFFF00">

<%
Class.forName("com.mysql.jdbc.Driver&quot

;
Connection myConn=DriverManager.getConnection("jdbc:mysql://localhost/test?user=root&password=root&quot

;
Statement stmt = myConn.createStatement();

String query = "SELECT count(messageNr) FROM messages";

ResultSet resultaat = stmt.executeQuery( query );

while(resultaat.next())
{

String Countresultaat = resultaat.getString("count(messageNr)&quot

;

}

%>

<form name="formAddMessage" method="post" action="addMessageOut.jsp">
<CENTER>TITEL:<BR>
<input type="text" name="inputMessageKop" size="40" maxlength="60">
<BR>
<BR>BERICHT:<BR>
<textarea name="inputMessageBody" cols="50" rows="20"></textarea>
<BR>
<input type="hidden" name="Begin" value = "<%= CountResultaat %>">
<input type="submit" name="Submit" value="Post Message">
<BR>

</form>

</body>
</html>

ERROR:

cannot resolve symbol variable CountResultaat
This refers to the "<input type="hidden" name="Begin" value = "<%= CountResultaat %>"> " part.

Can anyone please help me?
Thanks in advance!

Menno.

AR1982 · Jul 22, 2003

Menno

You need to change the variable in hidden name value to Countresultaat instead of CountResultaat because that is how you have it defined as:

String Countresultaat = resultaat.getString("count(messageNr)&quot

;

MPJH · Jul 22, 2003

Thanks for replying so fast, AR1982!
That was a silly typo

Still, when i change CountResultaat to something else (like 'a') it still gives me the same error. It looks like the variable just doesn't come out of the ResultSet. I still get the error (only then with 'a' instead of 'CountResultaat').

I read this solution on a website. I am trying to solve this 'count problem' without beans or cookies.

Thanks,
Menno.

AR1982 · Jul 22, 2003

Try making these changes

SELECT count(messageNr) as Count FROM messages

int Countresultaat = resultaat.getInt("Count&quot

;

String result = Countresultaat.toString();

input type="hidden" name="Begin" value = "<%= result %>">

MPJH · Jul 22, 2003

Hi,

COUNT FROM messages (or COUNT messageNr FROM messages) won't work since I use MySQL. (I tried it anyway).

When I use the following code in another file it works fine:

{
Class.forName("com.mysql.jdbc.Driver&quot

;
Connection myConn=DriverManager.getConnection("jdbc:mysql://localhost/test?user=root&password=root&quot

;
Statement stmt = myConn.createStatement();

String query = "SELECT count(messageNr) FROM messages";

ResultSet resultaat = stmt.executeQuery( query );

while(resultaat.next())
{

String aantalBerichten = resultaat.getString("count(messageNr)&quot

;
out.println(" Het aantal berichten is "+aantalBerichten+"&quot

;

}

When I use your modifications I get the following: int cannot be dereferenced String result = Countresultaat.toString();

and the same as before: cannot resolve symbol: variable result.

But what I want to do is not use the resulting value to print on screen, but to send it (via the form) to another page. (In the other JSP page I convert the String to int by the way... using Integer.parseInt("Begin&quot

)

That is my goal: get the result of the query and put it in a readable variable for the other page (without cookies or beans).

I hope you understand my question better now.

thanks again,
Menno.

vbkris · Jul 23, 2003

well the only problem i spotted in ur old code is this:
String Countresultaat = resultaat.getString("count(messageNr)&quot

;

change it to:
String Countresultaat = resultaat.getString("messageNr&quot

;

does it work now?

Known is handfull, Unknown is worldfull

libaax · Jul 23, 2003

I'm not an expert at this but, I think you need to put the String resultaat in a declaration so that it persists through out the page.
Hope that helps...
like so <%! String resultaat; %>

MPJH · Jul 23, 2003

Thanks for your responses vbkris and libaax,

the line:
String Countresultaat = resultaat.getString("count(messageNr)&quot

;

is not a problem, it delivers the data from the MySQL-database fine, I can use it in the same page perfectly.

The declaration of <%! String resultaat; %> works kind off, in the way that the error dissapears. The variable is now found by Apache. But the problem is, that the variable still is not updated by the SQL statement (to the string 200 or something) when it is sent to the next page. So the next page gives an error numberformatexception for input string: "null" .

I just can't seem to get the SQL value out of the page by using the HTML-form. I'll post the code so far (both pages this time):

CODE of the INPUTpage:

<%@ page language="java" contentType="text/html" import="java.sql.*" %>

<html>
<head>
<title>** Add message **</title>
</head>
<body>
<body bgcolor="#000000" text="#FF0000" link="#FFFF00" vlink="#FFFF00" alink="#FFFF00">

<%! String result; %>
<%
Class.forName("com.mysql.jdbc.Driver&quot

;
Connection myConn=DriverManager.getConnection("jdbc:mysql://localhost/test?user=root&password=root&quot

;
Statement stmt = myConn.createStatement();

String query = "SELECT count(messageNr) FROM messages";

ResultSet resultaat = stmt.executeQuery( query );

while(resultaat.next())
{

String result = resultaat.getString("count(messageNr)&quot

;

}

%>

<form name="formAddMessage" method="post" action="addMessageOut.jsp">
<CENTER>TITEL:<BR>
<input type="text" name="inputMessageKop" size="40" maxlength="60">
<BR>
<BR>BERICHT:<BR>
<textarea name="inputMessageBody" cols="50" rows="20"></textarea>
<BR>
<input type="hidden" name="Begin" value = "<%= result %>">
<input type="submit" name="Submit" value="Post Message">
<BR>

</form>

</body>
</html>

CODE of the OUTPUTpage:

<%@ page language="java" contentType="text/html" import="java.sql.*" %>

<html>
<head>
<title>** Add message **</title>
</head>
<body>

<body bgcolor="#000000" text="#FF0000" link="#FFFF00" vlink="#FFFF00" alink="#FFFF00">
<%

//het fantastische nieuwe cookie based herkennignssysteem

boolean loggedIn;
String naam;
Cookie[] cookies = request.getCookies();
naam = "Nee";

if (cookies != null) {
for(int i=0; i<cookies.length; i++) {
Cookie cookie = cookies;
if ("userIs".equals(cookie.getName()))
naam =(cookie.getValue());
}
}

String BeginB = request.getParameter("Begin"
int Begin = Integer.parseInt(BeginB);
int Nummer = ++Begin;

String messageKoppie = request.getParameter("inputMessageKop"
String messageBodytje = request.getParameter("inputMessageBody"

Class.forName("com.mysql.jdbc.Driver"
Connection myConn=DriverManager.getConnection("jdbc:mysql://localhost/test?user=root&password=root"
Statement stmt = myConn.createStatement();

String query = "INSERT INTO `messages` (`messageNr`, `messageKop`, `messagBody`, `author`) VALUES ('"+Nummer+"', '"+messageKoppie+"', '"+messageBodytje+"', '"+naam+"')";

ResultSet resultaat = stmt.executeQuery( query );

String redirectURL = "
http://localhost:8080/messageAdded.jsp";
response.sendRedirect(redirectURL);

%>

</body>
</html>

Thanks again!
Greetings,
Menno.

libaax · Jul 26, 2003

why declare result variable twice?
Also, I notice the host argument to the Database is missing port#
change this line:String result = resultaat.getString("count(messageNr)&quot

;
to :
result = resultaat.getString("count(messageNr)&quot

;

MPJH · Jul 27, 2003

Hi Libaax,

port# is not nescessary since I use the default.
First I declared result just once, but then I got the error that it was not found.

I'll try your advice.

Thnx,
Menno.

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Passing a JSP variable from a resultset into a HTMl form

MPJH

Programmer

AR1982

MIS

MPJH

Programmer

AR1982

MIS

MPJH

Programmer

vbkris

Programmer

libaax

Technical User

MPJH

Programmer

libaax

Technical User

MPJH

Programmer

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