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Thread: Search data....

  1. #1
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    Default Search data....

    Hi. Everyboy..

    This Is simple swing application for search data from the database using textbox..

    this is my code but getting some error.. any body help me....


    import java.awt.GridLayout;
    import java.awt.event.ActionEvent;
    import java.awt.event.ActionListener;
    import java.awt.event.WindowAdapter;
    import java.awt.event.WindowEvent;
    import java.sql.*;
    import java.util.logging.Level;
    import java.util.logging.Logger;
    import javax.swing.*;


    public class JavaApplication4 extends JFrame implements ActionListener{



    static JTextField FName,LName;
    static JButton btnSearch;

    static JPanel areapanel,bpanel,ipanel;

    private static Statement st = null;
    private static Connection con = null;
    private static ResultSet rs = null;


    JavaApplication4(){
    super("Student Information System");
    areapanel = new JPanel();
    areapanel.setLayout(new GridLayout(6,2,5,5));
    areapanel.add(new JLabel("First Name"));
    areapanel.add(FName = new JTextField(10));
    areapanel.add(new JLabel(""));
    areapanel.add(btnSearch = new JButton("Search"));
    areapanel.add(new JLabel("Last Name:"));
    areapanel.add(LName = new JTextField(10));


    ipanel = new JPanel();
    ipanel.setLayout(new GridLayout(3,2,10,10));
    ipanel.add(new JLabel(""));

    bpanel = new JPanel();
    bpanel.setLayout(new BorderLayout());
    bpanel.add(areapanel,BorderLayout.NORTH);
    bpanel.add(ipanel,BorderLayout.SOUTH);
    add(bpanel);

    btnSearch.addActionListener(this);
    }

    public static void main(String[] args) {
    JavaApplication4 mainapp = new JavaApplication4();
    mainapp.addWindowListener(new WindowAdapter(){
    public void windowClosing(WindowEvent e){
    System.exit(0);
    }
    });
    mainapp.setResizable(false);
    mainapp.setSize(575, 250);
    mainapp.setVisible(true);

    }
    public void retrieveRecords(){

    String fname = null,lname = null;


    try{
    con = getConnection();
    String query = "Select * from tblStudents where ID like '" + FName.getSelectedText() + "'";
    st = con.createStatement();
    ResultSet rs = st.executeQuery(query);

    while(rs.next()){

    // fname = rs.getString("FirstName");
    lname = rs.getString("LastName");

    }
    st.close();
    con.close();
    }

    catch(SQLException ex){
    System.err.println(ex.getMessage());
    }
    // FName.setText(fname);
    LName.setText(lname);



    if(FName.getText().equals("") && LName.getText().equals("")){
    JOptionPane.showMessageDialog(null,"Record Not Found!");
    FName.setText("");
    LName.setText("");
    }
    else
    FName.setText(fname);
    LName.setText(lname);

    }

    public static Connection getConnection()
    {
    try {
    Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
    } catch (ClassNotFoundException ex) {
    Logger.getLogger(JavaApplication4.class.getName()) .log(Level.SEVERE, null, ex);
    }
    return con;
    }
    public void actionPerformed(ActionEvent e){

    if(e.getSource() == btnSearch)
    {
    if(FName.getText().equals("")){
    JOptionPane.showMessageDialog(null,"no record to search!");
    }else{
    retrieveRecords();
    }
    }
    }

    }

    -----------------------------------------------------------------------------------
    Getting this error....:

    Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at javaapplication4.JavaApplication4.retrieveRecords( JavaApplication4.java:88)
    at javaapplication4.JavaApplication4.actionPerformed( JavaApplication4.java:136)
    at javax.swing.AbstractButton.fireActionPerformed(Abs tractButton.java:1995)
    at javax.swing.AbstractButton$Handler.actionPerformed (AbstractButton.java:2318)
    at javax.swing.DefaultButtonModel.fireActionPerformed (DefaultButtonModel.java:387)
    at javax.swing.DefaultButtonModel.setPressed(DefaultB uttonModel.java:242)
    at javax.swing.plaf.basic.BasicButtonListener$Actions .actionPerformed(BasicButtonListener.java:287)
    at javax.swing.SwingUtilities.notifyAction(SwingUtili ties.java:1636)
    at javax.swing.JComponent.processKeyBinding(JComponen t.java:2849)
    at javax.swing.JComponent.processKeyBindings(JCompone nt.java:2884)
    at javax.swing.JComponent.processKeyEvent(JComponent. java:2812)
    at java.awt.Component.processEvent(Component.java:599 3)
    at java.awt.Container.processEvent(Container.java:204 1)
    at java.awt.Component.dispatchEventImpl(Component.jav a:4583)
    at java.awt.Container.dispatchEventImpl(Container.jav a:2099)
    at java.awt.Component.dispatchEvent(Component.java:44 13)
    at java.awt.KeyboardFocusManager.redispatchEvent(Keyb oardFocusManager.java:1848)
    at java.awt.DefaultKeyboardFocusManager.dispatchKeyEv ent(DefaultKeyboardFocusManager.java:704)
    at java.awt.DefaultKeyboardFocusManager.preDispatchKe yEvent(DefaultKeyboardFocusManager.java:969)
    at java.awt.DefaultKeyboardFocusManager.typeAheadAsse rtions(DefaultKeyboardFocusManager.java:841)
    at java.awt.DefaultKeyboardFocusManager.dispatchEvent (DefaultKeyboardFocusManager.java:668)
    at java.awt.Component.dispatchEventImpl(Component.jav a:4455)
    at java.awt.Container.dispatchEventImpl(Container.jav a:2099)
    at java.awt.Window.dispatchEventImpl(Window.java:2475 )
    at java.awt.Component.dispatchEvent(Component.java:44 13)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java: 599)
    at java.awt.EventDispatchThread.pumpOneEventForFilter s(EventDispatchThread.java:269)
    at java.awt.EventDispatchThread.pumpEventsForFilter(E ventDispatchThread.java:184)
    at java.awt.EventDispatchThread.pumpEventsForHierarch y(EventDispatchThread.java:174)
    at java.awt.EventDispatchThread.pumpEvents(EventDispa tchThread.java:169)
    at java.awt.EventDispatchThread.pumpEvents(EventDispa tchThread.java:161)
    at java.awt.EventDispatchThread.run(EventDispatchThre ad.java:122)


  2. #2
    Super Moderator Norm's Avatar
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    Default Re: Search data....

    Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at javaapplication4.JavaApplication4.retrieveRecords( JavaApplication4.java:88)
    There is a variable with a null value at line 84. Look at that line and determine what variable has a null value and then backtrack in the code to find out why that variable does not have a valid value.

    If you can not tell what variable is null, add a println just before line 88 and print the value of all variables on line 88.

    Please Edit your post and wrap your code with[code=java]<YOUR CODE HERE>[/code] to get highlighting
    If you don't understand my answer, don't ignore it, ask a question.

  3. #3
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    Default Re: Search data....

    Quote Originally Posted by Norm View Post
    There is a variable with a null value at line 84. Look at that line and determine what variable has a null value and then backtrack in the code to find out why that variable does not have a valid value.

    If you can not tell what variable is null, add a println just before line 88 and print the value of all variables on line 88.

    Please Edit your post and wrap your code with[code=java]<YOUR CODE HERE>[/code] to get highlighting

    If I m not intialised my value as null. at line 84
    then got the error to intialised a value when i put that value
    in the if condition..

  4. #4
    Super Moderator Norm's Avatar
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    Default Re: Search data....

    What variable has the null value? Where do you give that variable a value?

    You can not use a variable with a null value to reference methods in a class. THe variable must have a valid non-null value.

    Please Edit your post and wrap your code with[code=java]<YOUR CODE HERE>[/code] to get highlighting
    If you don't understand my answer, don't ignore it, ask a question.

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