Recupérer la valeur d'un JCOmbobox

**boutheinanabeul** · 22/08/2016, 22h34

Bonjour,

Je voudrais récupérer la valeur d'un JCombobox et en se basant sur cette valeur je veux extraire un champ de la base de donnée et comparer avec celui introduit par l'utilisateur si il est inférieur ou bien égale la commande est validé sinon on refuse.
Voici le code

Code :

Sélectionner tout - Visualiser dans une fenêtre à part

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
@Override
		public void actionPerformed(ActionEvent evt) {
			// TODO Auto-generated method stub
			if(evt.getSource()==b1){
				int x=Integer.parseInt(text1.getText());
				String a= liste.getSelectedItem().toString();
			try	{
					Class.forName("com.mysql.jdbc.Driver");
 
					laConnection =  (Connection) DriverManager.getConnection("jdbc:mysql://localhost/application?useSSL=false","boutheina","30071986"); 
 
					String  sql = "select quantite from produit where designation=?";
					PreparedStatement statement = laConnection.prepareStatement(sql);
					 statement.setObject(1, a);
					try(ResultSet Rs = statement.executeQuery()) {
						if(Rs.getInt("quantite")>=x){
							JOptionPane.showMessageDialog(null, "Your Command is validated, you can pay", 
	  		                        "InformationMessage",
	  		                        JOptionPane.INFORMATION_MESSAGE);}
 
 
					else
					{
						JOptionPane.showMessageDialog(null, "An error appears in the inscription: the ID of the product already exist ", 
  		                        "Error Message",
  		                        JOptionPane.ERROR_MESSAGE);}
 
 
			    }
			    catch
				(Exception e)
				{
				            System.out.print("impossible de se connecter à la base");
				            e.printStackTrace();
 
				} 
				}
			catch
			(Exception e)
			{
			            System.out.print("impossible de se connecter à la base");
			            e.printStackTrace();}
			}
 
			if(evt.getSource()==b2){
				System.exit(0);
			}
 
		}
}

Voici l'erreur affiché:
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at Distributeur.Order.actionPerformed(Order.java:141)
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$000(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)