Re: Using BLOB fields with JPA

From:

carmelo <csaffi@tiscali.it>

Newsgroups:

comp.lang.java.programmer

Date:

Thu, 7 May 2009 07:16:38 -0700 (PDT)

Message-ID:

<a312858b-f6af-4fc1-b4dc-6e9445ebb990@t11g2000vbc.googlegroups.com>

On 7 Mag, 02:50, Arne Vajh=F8j <a...@vajhoej.dk> wrote:

carmelo wrote:

I'd like to have your suggestions on how to work with a BLOB field on
a MySql db, on which I need to store an image, using JPA.

The table is:
MyTable(id, code, description, BLOB image)

I developed a Swing app using Netbeans 6.5.1, making binding between
MyTable fields and some JTextFields. The JPA implementation used is
TopLink.

How can I do to store the imagi into the BLOB field?

http://www.oracle.com/technology/products/ias/toplink/jpa/resources/t...

Arne

Thank you for your answer Arne.
I was able to define the blob field using JPA. My problem is that I'm
not able to store the picture, using data binding.

I'm trying to write a Converter class, but I get runtime casting
errors. The Converter class is this:

public class ImageConverter extends Converter
{
    //byte to image
    public ImageIcon convertForward(Object arg)
    {
        Image image = new ImageIcon( ( byte[] ) arg ).getImage()
                            .getScaledInstance( 50, 50,
Image.SCALE_SMOOTH );

        return new ImageIcon( image );
    }

    //image to byte
    public byte[] convertReverse(Object arg)
    {
        ImageIcon image = (( ImageIcon ) arg );
        String s = image.toString();
        byte[] b = new byte[s.length()];
        for(int i=0; i<s.length(); i++)
            b[i] = (byte)s.charAt(i);

        return b;
    }
}

The stack trace is this:

Caused by: org.jdesktop.beansbinding.PropertyResolutionException:
Error evaluating EL expression ValueExpression[$
{selectedElement.image}] on javax.swing.JTable[masterTable,
0,0,406x48,alignmentX=0.0,alignmentY=0.0,border=,flags=251658568,ma=
ximumSize=,minimumSize=,preferredSize=,autoCreateColumnsFromModel=t=
rue,autoResizeMode=AUTO_RESIZE_SUBSEQUENT_COLUMNS,cellSelectionEnabled==
false,editingColumn=-1,editingRow=-1,gridColor=javax.swing.plaf.Color=
UIResource
[r=128,g=128,b=128],preferredViewportSize=java.awt.Dimension
[width=450,height=400],rowHeight=16,rowMargin=1,rowSelectionAllowed=
=true,selectionBackground=javax.swing.plaf.ColorUIResource
[r=49,g=106,b=197],selectionForeground=javax.swing.plaf.ColorUIReso=
urce
[r=255,g=255,b=255],showHorizontalLines=true,showVerticalLines=tr=
ue]
        at org.jdesktop.beansbinding.ELProperty.setValue
(ELProperty.java:507)
        at org.jdesktop.beansbinding.Binding.saveUnmanaged
(Binding.java:1275)
        at org.jdesktop.beansbinding.Binding.save(Binding.java:1254)
        at org.jdesktop.beansbinding.AutoBinding.trySaveThenRefresh
(AutoBinding.java:176)
        at org.jdesktop.beansbinding.AutoBinding.targetChangedImpl
(AutoBinding.java:249)
        at org.jdesktop.beansbinding.Binding.targetChanged
(Binding.java:1433)
        at org.jdesktop.beansbinding.Binding.access$1300(Binding.java:
38)
        at org.jdesktop.beansbinding.Binding$PSL.propertyStateChanged
(Binding.java:1620)
        at
org.jdesktop.beansbinding.PropertyHelper.firePropertyStateChange
(PropertyHelper.java:212)
        at org.jdesktop.beansbinding.BeanProperty.notifyListeners
(BeanProperty.java:712)
        at org.jdesktop.beansbinding.BeanProperty.access$1000
(BeanProperty.java:143)
        at org.jdesktop.beansbinding.BeanProperty
$SourceEntry.cachedValueChanged(BeanProperty.java:369)
        at org.jdesktop.beansbinding.BeanProperty
$SourceEntry.propertyValueChanged(BeanProperty.java:409)
        at org.jdesktop.beansbinding.BeanProperty
$SourceEntry.propertyChange(BeanProperty.java:414)
        at java.beans.PropertyChangeSupport.firePropertyChange
(PropertyChangeSupport.java:339)
        at java.beans.PropertyChangeSupport.firePropertyChange
(PropertyChangeSupport.java:276)
        at java.awt.Component.firePropertyChange(Component.java:7868)
        at javax.swing.JLabel.setIcon(JLabel.java:371)
        at
desktopapplication_blob.DesktopApplication_BLOBView.setPicture
(DesktopApplication_BLOBView.java:574)
        at
desktopapplication_blob.DesktopApplication_BLOBView.showOpenFileDialog
(DesktopApplication_BLOBView.java:558)
        ... 32 more
Caused by: org.jdesktop.el.ELException: java.lang.ClassCastException
        at org.jdesktop.el.BeanELResolver.setValue(BeanELResolver.java:
335)
        at org.jdesktop.beansbinding.TempELContext
$BeanDelegateELResolver.setValue(TempELContext.java:87)
        at org.jdesktop.el.CompositeELResolver.setValue
(CompositeELResolver.java:265)
        at org.jdesktop.el.impl.parser.AstValue.setValue(AstValue.java:
133)
        at org.jdesktop.el.impl.ValueExpressionImpl.setValue
(ValueExpressionImpl.java:259)
        at org.jdesktop.beansbinding.ELProperty.setValue
(ELProperty.java:505)
        ... 51 more
Caused by: java.lang.ClassCastException
        at java.lang.Class.cast(Class.java:2990)
        at org.jdesktop.beansbinding.Binding.convertForward
(Binding.java:1312)
        at org.jdesktop.beansbinding.Binding.getSourceValueForTarget
(Binding.java:844)
        at org.jdesktop.beansbinding.Binding.refreshUnmanaged
(Binding.java:1222)
        at org.jdesktop.beansbinding.Binding.refresh(Binding.java:
1207)
        at org.jdesktop.beansbinding.AutoBinding.tryRefreshThenSave
(AutoBinding.java:162)
        at org.jdesktop.beansbinding.AutoBinding.sourceChangedImpl
(AutoBinding.java:227)
        at org.jdesktop.beansbinding.Binding.sourceChanged
(Binding.java:1411)
        at org.jdesktop.beansbinding.Binding.access$1200(Binding.java:
38)
        at org.jdesktop.beansbinding.Binding$PSL.propertyStateChanged
(Binding.java:1618)
        at
org.jdesktop.beansbinding.PropertyHelper.firePropertyStateChange
(PropertyHelper.java:212)
        at org.jdesktop.beansbinding.ELProperty.notifyListeners
(ELProperty.java:688)
        at org.jdesktop.beansbinding.ELProperty.access$800
(ELProperty.java:155)
        at org.jdesktop.beansbinding.ELProperty
$SourceEntry.processSourceChanged(ELProperty.java:312)
        at org.jdesktop.beansbinding.ELProperty
$SourceEntry.sourceChanged(ELProperty.java:326)
        at org.jdesktop.beansbinding.ELProperty
$SourceEntry.propertyChange(ELProperty.java:333)
        at java.beans.PropertyChangeSupport.firePropertyChange
(PropertyChangeSupport.java:339)
        at java.beans.PropertyChangeSupport.firePropertyChange
(PropertyChangeSupport.java:276)
        at desktopapplication_blob.Prova.setImage(Prova.java:57)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke
(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke
(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at org.jdesktop.el.BeanELResolver.setValue(BeanELResolver.java:
330)
        ... 56 more