login update problem

#1
mutago

Posted 22 March 2011 - 08:57 PM

Programmer

Members
102 posts

good day everybody, i want to used this code for users login but each time i want the count column to update, it will return an empty page. I know may be i did not structure
this code properly especially


String query1="UPDATE vata SET count = count + 1 WHERE username='"+username+"'";

 int i = stmt.executeUpdate(query1);

below is the main code



<%@ page import="java.sql.*" %> 

<%@ page import="java.io.*" %> 

<html> 

<head> 

    <title>login</title>

</head> 

<body>

<%  

response.setContentType("text/html");

PrintWriter pw = response.getWriter();

String username = request.getParameter("username");

String password = request.getParameter("password");

int count=0;


try{




 Class.forName("com.mysql.jdbc.Driver").newInstance();



Connection con=null;

ResultSet rst=null;

Statement stmt=null;



con=DriverManager.getConnection("jdbc:mysql://localhost:3306/vat", "root", "root");




stmt=con.createStatement();

String query = "select count from vat where username='"+username+"' and password='"+password+"'";

System.out.println(query);

ResultSet rs = stmt.executeQuery(query);

while(rs.next()){

//count=rs.getInt(1);

}

if(count > 1){

pw.println("<font color=green size=5>you cannot login again</font>");

}

else{

String query1="UPDATE vata SET count = count + 1 WHERE username='"+username+"'";

 int i = stmt.executeUpdate(query1);		

pw.println("<font color=red size=5>welcome friend</font>");

}

}


catch(Exception e){

System.out.println(e.getMessage());

}



%> 



thank u

#2
wim DC

Posted 23 March 2011 - 01:33 AM

Writes binary right handed and hex left handed

Members
2,084 posts

Programming Language:Java, JavaScript, PL/SQL
Learning:Java

Are you sure the table name is "vata", as in the first query you use "vat"?

#3
mutago

Posted 23 March 2011 - 12:27 PM

Programmer

Members
102 posts

the table is not the problem. I think the problem is how to perform both insert and update simultaneously.

#4
wim DC

Posted 24 March 2011 - 04:42 AM

Writes binary right handed and hex left handed

Members
2,084 posts

Programming Language:Java, JavaScript, PL/SQL
Learning:Java

mutago said:

the table is not the problem. I think the problem is how to perform both insert and update simultaneously.

What insert?

I don't think there's anything wrong with the code.
Why is //count=rs.getInt(1); commented out, if a column named "count" exists in the vat table, then it should work just fine.
If it doesn't exist, then I think you need


SELECT COUNT(*) 

FROM vat 

WHERE username= 'wim' and password='DC'

which leads to this string for your query:


"select count(*) from vat where username='"+username+"' and password='"+password+"'"

#1 mutago Posted 22 March 2011 - 08:57 PM

#2 wim DC Posted 23 March 2011 - 01:33 AM

#3 mutago Posted 23 March 2011 - 12:27 PM

#4 wim DC Posted 24 March 2011 - 04:42 AM

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#1
mutago

Posted 22 March 2011 - 08:57 PM

#2
wim DC

Posted 23 March 2011 - 01:33 AM

#3
mutago

Posted 23 March 2011 - 12:27 PM

#4
wim DC

Posted 24 March 2011 - 04:42 AM