Getting 'null' value in response to statement.executeUpdate method

[Nikhil B. Singh]

Hello,

I am trying to insert few records in to mysql database. As i can successfully able to establish connection with server but not able to insert a single record through net beans ide gui interface or front end.

The code which i wrote for connection is encapsulated in Constructor method and in event handler i have written code to insert data. this code is as follows:

private void btn_addActionPerformed(java.awt.event.ActionEvent evt) {                                        

    try{
    String name, course,... team_t;  //JOptionPane.showMessageDialog(null, "You have clicked me");

//verifying if connection is successful.
    //if(!(txt_name.equals(null))){
//    if(conx!= null){
            //   JOptionPane.showMessageDialog(null,"Connection has established","I N F O",JOptionPane.INFORMATION_MESSAGE);
            // executes successfully
            //        } 

// reading value from swing components.

    name = txt_name.getText();
     
    if(cmb_course_name.getSelectedIndex() != 0 && cmb_course_name.getSelectedIndex() != 1)
    {
         course = cmb_course_name.getSelectedItem().toString();
    }
    else
    {
        course = "n/a";
    }
     .
     . 
     .
     .
    if(rbtn_indiv.getName().equals("Individual"))
    {
        team_t = "Individual";
    }
    else{
        team_t = "Individual";
    }
    

    int r = 0;
    statement = conx.createStatement();
    //String ins_qry = "insert into stud_info (s_name, s_course,s_college,s_cont, s_email,s_team,s_prj_name) values ('"+name+"','"+course+"','"+col_n+"','"+cont_n+"','"+email_i+"','"+team_t+"','"+prj_name+"')";

    r  =     statement.executeUpdate("insert into stud_info (s_name ... s_team) values ('"+name+"' ...  '"+team_t+"')");
    if(r == 1)
    {
     JOptionPane.showMessageDialog(null, "Successful"+r,"query success",JOptionPane.INFORMATION_MESSAGE);
    }
    else
    {
    JOptionPane.showMessageDialog(null," ,failure . "+r," Query failure",JOptionPane.INFORMATION_MESSAGE);
    }
    }
    catch(Exception ex)
    {
        JOptionPane.showMessageDialog(null,"ERROR MESSAGE "+ex.getStackTrace(),"Save Error",JOptionPane.ERROR_MESSAGE);
    }
    finally{
    try{
        conx.close();
    }catch(Exception ex){
        JOptionPane.showMessageDialog(null,"closing time err"+ex.getMessage() ,"E R R O R",JOptionPane.ERROR_MESSAGE);
    }
    }
}                                       

in this it throws an exception error and "r" yields null. I am confused where the hell i have made mistake that it is giving me null as output instead of 0 or 1.

Thank you!

[Nicola Garofalo]

Could you please post the exception message, if any, and exception type?

[Nikhil B. Singh]

Hi..!!

actually i wrote these code in try -catch block, so it is not generating much verbose however as i have use stack trace method it generates following messaga: Ljava.lang.StackTraceElement;@d49271

Thank you for quick response.!!

[Nicola Garofalo]

Nikhil B. Singh wrote:Hi..!!

actually i wrote these code in try -catch block, so it is not generating much verbose however as i have use stack trace method it generates following messaga: Ljava.lang.StackTraceElement;@d49271

Thank you for quick response.!!

If you can't debug your code just add after line 53:

ex.printStackTrace();

And see what is printed on your output. You should see the exception type, and probably where exactly it has been generated.

[Nikhil B. Singh]

.
.
.
If you can't debug your code just add after line 53:

ex.printStackTrace();

And see what is printed on your output. You should see the exception type, and probably where exactly it has been generated.

java.lang.NullPointerException
	at StudentInformation.btn_addActionPerformed(StudentInformation.java:327)
	at StudentInformation.access$100(StudentInformation.java:18)
	at StudentInformation$2.actionPerformed(StudentInformation.java:117)
	at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
	at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
	at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
	at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
	at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
	at java.awt.AWTEventMulticaster.mouseReleased(AWTEventMulticaster.java:289)
	at java.awt.Component.processMouseEvent(Component.java:6504)
	at javax.swing.JComponent.processMouseEvent(JComponent.java:3321)
	at java.awt.Component.processEvent(Component.java:6269)
	at java.awt.Container.processEvent(Container.java:2229)
	at java.awt.Component.dispatchEventImpl(Component.java:4860)
	at java.awt.Container.dispatchEventImpl(Container.java:2287)
	at java.awt.Component.dispatchEvent(Component.java:4686)
	at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
	at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
	at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
	at java.awt.Container.dispatchEventImpl(Container.java:2273)
	at java.awt.Window.dispatchEventImpl(Window.java:2713)
	at java.awt.Component.dispatchEvent(Component.java:4686)
	at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:707)
	at java.awt.EventQueue.access$000(EventQueue.java:101)
	at java.awt.EventQueue$3.run(EventQueue.java:666)
	at java.awt.EventQueue$3.run(EventQueue.java:664)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
	at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
	at java.awt.EventQueue$4.run(EventQueue.java:680)
	at java.awt.EventQueue$4.run(EventQueue.java:678)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
	at java.awt.EventQueue.dispatchEvent(EventQueue.java:677)
	at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:211)
	at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:128)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:117)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:113)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:105)
	at java.awt.EventDispatchThread.run(EventDispatchThread.java:90)
BUILD SUCCESSFUL (total time: 22 seconds)

I am sorry, i could not get understand much from this, if you don't mind, would you please help me to catch the error source.

Thank you!

[Nicola Garofalo]

Nikhil B. Singh wrote:Hi..!!

actually i wrote these code in try -catch block, so it is not generating much verbose however as i have use stack trace method it generates following messaga: Ljava.lang.StackTraceElement;@d49271

Thank you for quick response.!!

Anyway
getStackTrace() method returns an array of StackTraceElement.
So it's useless to print it out or use it as a message for a message Panel.

[Nicola Garofalo]

Much more clearer now

See your class StudentInformation.java at line 327.

What are you doing there? What instructions are you trying to execute?

[Nikhil B. Singh]

at line 327: I am writing code to get a value from radio button. I have two radio button controls and trying to read the selected one value.

if(rbtn_indiv.getName().equals("Individual"))
    {
        team_t = "Individual";
    }
    else{
        team_t = "Individual";
    }

Please let me know if I am writing wrong syntax to read the value of selected radio button.

Thank you!

[Nicola Garofalo]

Ok either radion button rbtn_indiv is null or rbtn_indiv.getName() is null.

did you make somewhere before line 327

rbtn_indiv = new JRadioButton(..) ?

Did you set the name of your JRadioButton?

That's the heart of your problem

Let me know if you want.

[Nikhil B. Singh]

Hi..

As you have suggested I examined that radio button code again, as generated in Net beans ide auto code generated section..

I have set the name property as i have given in radio button's text property field.

However, i am facing new kind of error, which is as follows

Uncompilable source code - variable team_t might not have been initialized.


I think, i m not reading value of selected radio button properly. Please throw some light to do perform this.

Thank you !!

[Nicola Garofalo]

Nikhil B. Singh wrote:Hi..

As you have suggested I examined that radio button code again, as generated in Net beans ide auto code generated section..

I have set the name property as i have given in radio button's text property field.

However, i am facing new kind of error, which is as follows

Uncompilable source code - variable team_t might not have been initialized.


I think, i m not reading value of selected radio button properly. Please throw some light to do perform this.

Thank you !!

You must assign a value to every local variable.
So give team_t an initial value

for example:

team_t = null;

if(rbtn_indiv.getName().equals("Individual"))
    {
        team_t = "Individual";
    }
    else{
        team_t = "Individual";
    }

In the code above you are always giving to String team_t the value "Individual"

Why?

[Nikhil B. Singh]

Hi..

actually i have wrote that text mistakenly. however i have improved this mistake but the code i have written here to get the value of selected radio button is not working properly. this is why it is giving null pointer exception error.

I am confused that why these people have given Label & Name property associated with any swing component. It doesn't make any sense to set Text property and Label property separately.

plus i could not resolve this when we should use getText or getSelectedObjects method for radio button or which may be appropriate for radio button to identify selected radio button.

Thanks!!

[Nikhil B. Singh]

Hi..

I have figured out the solution to read the value of selected radio button.
it is as follows:

if(radioButton.isSelected())
{
//true part
}
else{
//false part
}

Thank you very much for your kind support...!

With regards!

Nikhil!

[Nicola Garofalo]

For future doubts you may refer to java tutorial

http://docs.oracle.com/javase/tutorial/uiswing/components/button.html

Bye,
Nicola