Java database display randomly

Question

private void Label_GenerateMouseClicked(java.awt.event.MouseEvent evt) {                                            
    // TODO add your handling code here:
    try{
        String sql = "select from Account ORDER BY RAND()";
        PreparedStatement st = con.prepareStatement(sql);
        ResultSet rs = st.executeQuery();

        if(rs.next()){
            TextField_Username.setText(rs.getString("EMAIL"));
            TextField_Password.setText(rs.getString("PASSWORD"));
        }
    }catch(Exception e){
        System.out.println("Cannot generate.");
    }
}

This code keep catching the error and i cant figure out why. im gettign error java.lang.NullPointerException. Please help

use `System.out.println("Cannot generate." + e.getMessage());` to see real error — Tamil Selvan C, May 22 '15 at 17:26
What is the error? Could you paste your stack trace. There can be null pointer exception on PreparedStatement, ResultSet, ... — Bosko Mijin, May 22 '15 at 17:26
use `String sql = "select * from Account ORDER BY RAND()";` as per @AmineZaine comment — Tamil Selvan C, May 22 '15 at 17:38

score 2 · Accepted Answer · answered May 22 '15 at 17:41

2

NVM GUYS I FIGURED IT OUT. I DIDNT RUN MY CONNECTION FUNCTION. srry for the troubles.

answered May 22 '15 at 17:41

NgoCuong

2,169
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1

Still, there are a number of other issues with your code, including the fact that your SQL statement is broken. See comments and additional answers. – Shotgun Ninja May 22 '15 at 17:44

score 0 · Answer 2 · answered May 22 '15 at 17:40

Try this :

String sql = "select EMAIL,PASSWORD from Account ORDER BY RAND()";
        PreparedStatement st = con.prepareStatement(sql);
        ResultSet rs = st.executeQuery();

        if(rs.next()){
            TextField_Username.setText(rs.getString("EMAIL"));
            TextField_Password.setText(rs.getString("PASSWORD"));
        }

score 0 · Answer 3 · answered May 22 '15 at 17:41

First off, your SQL statement is incorrect. Instead of

"select from Account ORDER BY RAND()"

it should be

"select Email, Password from Account ORDER BY RAND()"

When doing a select, you need to specify either the columns being selected, or use * to specify all tables. Production SQL code should never do a SELECT *, though; you should only specify which columns you're actually using to avoid leaking data and wasting time.

Also, I hope that Password column has its data encrypted...

Java database display randomly

3 Answers3