Java / MySQL null pointer exception halfway through resultset [duplicate]

Question

I have a java based epos system in use within my company and am presently writing a series of Java apps for use in the back office / warehouse. The purpose of my current project is to extract an Image (saved as a blob), and a title (varchar value) from MYSQL and display each of these on JLabels within a JPanel.

First the sql query is handled within a class called DataLogic like so:

public class DataLogic {

MySQLConnect mysqlConnect = new MySQLConnect();
private Connection connect = null;
private PreparedStatement preparedStatement = null;

public ResultSet getCategories(){
    try {
 connect = mysqlConnect.connDatabase();    
 preparedStatement = connect.prepareStatement("SELECT image, name, texttip from CATEGORIES ORDER BY name");
 ResultSet resultSet = preparedStatement.executeQuery();
    return resultSet;
    } catch (Exception e){
    }
    return null;
}

}

AS you can see the get Categories function returns a ResultSet which is used in the populateCats() function of a class called GuiEvents, the relevant section of which is below:

public void populateCats(){
    results = dataLogic.getCategories();
    try{
        int count = 0;
        while (results.next()) {
            ++count;   // Get data from the current row and use it
        } 
        results.first();
        while (results.next()){
            GridLayout catLayout = new GridLayout(count,2);
            System.out.println(count);
            gui.catList.setLayout(catLayout);
            JLabel catLabel = new JLabel(results.getString(2));
            JLabel imgLabel = new JLabel();
            imgLabel.setIcon(displayImage(results.getBytes(1)));
            gui.catList.add(imgLabel);
            gui.catList.add(catLabel);
        }
    } catch (Exception e) {
         e.printStackTrace();
    }
}

public ImageIcon displayImage(byte[] bytes) {
Image img = Toolkit.getDefaultToolkit().createImage(bytes);

// new code
int imgHeight = img.getHeight(null);
int imgWidth = img.getWidth(null);
int newHeight = imgHeight / 2;
int newWidth = imgWidth / 2;
//System.out.println(imgHeight + "," + imgWidth);
Image resizedImg = img.getScaledInstance(40,40,Image.SCALE_SMOOTH );
//end new code

ImageIcon icon = new ImageIcon(resizedImg);
return icon;
}

My problem is that although it compiles and runs i get the following error within netbeans:

java.lang.NullPointerException
    at java.awt.Toolkit.createImage(Toolkit.java:1111)
    at gapricing.app.first.GuiEvents.displayImage(GuiEvents.java:48)
    at gapricing.app.first.GuiEvents.populateCats(GuiEvents.java:39)
    at gapricing.app.first.Gui.<init>(Gui.java:111)
    at gapricing.app.first.Main.main(Main.java:6)

and whilst 29 of the images and titles are displayed exactly as I would have liked the remianing 9 do not although thanks to the gridlayout 9 empty boxes are included at the bottom of the JPanel. Can anyone help pls??

agree that bytes are null. Try to add 'WHERE image IS NOT NULL' to your SQL and see it helps — Stan
– Stan, Commented May 12, 2015 at 14:42

danparker · Accepted Answer · 2015-05-12 14:54:34Z

1

thanks guys yes an image was missing from db.
Simple edit:

if (results.getBytes(1) != null){
imgLabel.setIcon(displayImage(results.getBytes(1)));
}

If bytes are null it just dispalys an empty label. Thanks alot

answered May 12, 2015 at 14:54

danparker

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