I'm trying insert values into MySQL database, getting NullPointerException

Question

I'm trying to insert some data captured by a gui form into my database. When I run the program, and try to add a vendor, I'm getting a nullpointerexception, and am having trouble figuring out why. Any guidance is greatly appreciated.

Java Method:

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

         addVendorPanel.setVisible(true);

         //ANDY:
         String vendorName = addVendorNameField.getText();
         String customerName = addCustomerNumField.getText();
         String vendorCode = addVendorCodeField1.getText();

     String sql = "INSERT INTO VENDORS (Vendor,Cust#,Vendorcode)"+"VALUES('"+vendorName+"','"+customerName+"','"+vendorCode+"')";
     try {
         openconnection();
         rs = statement.executeQuery(sql);
     } catch (SQLException ex) {
         Logger.getLogger(gui.class.getName()).log(Level.SEVERE, null, ex);
     }
}

OpenConnection:

public void openconnection(){
     Connection conn = null;
        try {
      conn = DriverManager.getConnection("jdbc:mysql://sql3.freemysqlhosting.net:3306/sql376856", "xxxx","xxxxx");
      System.out.println("Connected database successfully...");
        } catch (Exception e) {
            System.out.println(e);
        }
    try {
        Statement statement = conn.createStatement();
    } catch (SQLException ex) {
        Logger.getLogger(gui.class.getName()).log(Level.SEVERE, null, ex);
    }
}

Declare Global Variables for Use:

public class gui extends javax.swing.JFrame {


 Statement statement;  
 Connection conn;
 ResultSet rs;
/**
 * Creates new form gui
 */
public gui() {
    initComponents();
}

Error Message:

run:
Connected database successfully...
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at database.gui.addVendorToDbButtonActionPerformed(gui.java:1142)
at database.gui.access$1300(gui.java:23)
at database.gui$14.actionPerformed(gui.java:562)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022)
at        javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2346)
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.Component.processMouseEvent(Component.java:6527)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3321)
at java.awt.Component.processEvent(Component.java:6292)
at java.awt.Container.processEvent(Container.java:2234)
at java.awt.Component.dispatchEventImpl(Component.java:4883)
at java.awt.Container.dispatchEventImpl(Container.java:2292)
at java.awt.Component.dispatchEvent(Component.java:4705)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4898)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4533)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4462)
at java.awt.Container.dispatchEventImpl(Container.java:2278)
at java.awt.Window.dispatchEventImpl(Window.java:2739)
at java.awt.Component.dispatchEvent(Component.java:4705)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:746)
at java.awt.EventQueue.access$400(EventQueue.java:97)
at java.awt.EventQueue$3.run(EventQueue.java:697)
at java.awt.EventQueue$3.run(EventQueue.java:691)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:86)
at java.awt.EventQueue$4.run(EventQueue.java:719)
at java.awt.EventQueue$4.run(EventQueue.java:717)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:716)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)

have you created objects, for addVendorPanel, addVendorNameField, addCustomerNumField or addVendorCodeField or statement? ? — Prasad Kharkar
– Prasad Kharkar, Commented May 12, 2015 at 4:48
Statement and connection is not instantiated in your local method — shinjw
– shinjw, Commented May 12, 2015 at 4:52

kondu · Accepted Answer · 2015-05-12 04:59:56Z

1

I think your statement variable in the method addVendorToDbButtonActionPerformed is null and hence the nullpointer exception.

answered May 12, 2015 at 4:59

kondu

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shinjw · Accepted Answer · 2015-05-12 05:13:32Z

0

public void openconnection(){
        try {
      conn = DriverManager.getConnection("jdbc:mysql://sql3.freemysqlhosting.net:3306/sql376856", "xxxx","xxxxx");
      System.out.println("Connected database successfully...");
        } catch (Exception e) {
            System.out.println(e);
        }
    try {
        statement = conn.createStatement();
    } catch (SQLException ex) {
        Logger.getLogger(gui.class.getName()).log(Level.SEVERE, null, ex);
    }
}

if you go this route. make sure you make another method to close your connection.

I'd also recommend moving statement = conn.createStatement(); to the method where you defined your query. Make sure you close the statement and result set in that method after retrieving your results.

edited May 12, 2015 at 5:13

answered May 12, 2015 at 4:56

shinjw

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5 Comments

user2977729 Over a year ago

Is there another way to create a connection the entire time the program is running? Instead of just on button click

MadProgrammer Over a year ago

@user2977729 Cache the result of the connection, so when you ask for the connection again, return the one you have already opened (by checking to see if the value is null or not)

shinjw Over a year ago

Look up "JDBC Connection Pooling"

user2977729 Over a year ago

@shinjw I tried changing the return type of openconnection() to statement, and changing it to statement = openconnection(); in the method. Getting the same error.... should I handle this a different way?

shinjw Over a year ago

post your new method. are you returning conn.createStatement() in that method?

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