get data from resultset after the execution of sql query in netbeans - sql

Question

I have created a table register in SQL with field username. In the JFrame when a user enters username there is a JButton for checking the username availability. For this I have used the code below:
String sqlstmt = "select username from register where username='" +
jTextField1.getText() + "'";
try {
st = con.prepareStatement(sqlstmt);
stmt = con.createStatement();
rs = st.executeQuery(sqlstmt);
if (rs.next()) {
JOptionPane.showMessageDialog(null,"found");
} else {
JOptionPane.showMessageDialog(null,"not found");
}
} catch(SQLException e) {
JOptionPane.showMessageDialog(null,"sql error");
}
when executing this query, it is seen that data is empty. Or if I put rs.getString("username") inside the if (rs.next), it shows the "sql error" message.

Answer 1

You're mixing Statements and PreparedStatements here.
The best approach here would probably be to use a PreparedStatement, which would take care of any funky characters from your input, and offer protection against SQL injection:
// SQL statement to prepare.
// Note the lack of single quotes (') in the parameter
String sqlstmt= "select username from register where username = ?";
// Prepare the statement
PreparedStatement st = con.prepareStatement(sqlstmt);
// Bind the argument
st.setString(1, jTextField1.getText());
// Execute
ResultSet rs = st.executeQuery();
// Rest of the code to handle results...
Note:
This example omits error handling (e.g., try-catch constructs) in favor of clarity.