• IUncachedImageField (a copy of IImagegeField)
  
• IUncachedImageFieldUIFacade (a copy of IImageFieldUIFacade)
  
• UncachedImageFieldEvent (a copy of ImageFieldEvent)
  
• UncachedImagedFieldListener (a copy of ImageFieldListener)
  
• AbstractUncachedImageField (a copy of AbstractImageField)
  

• ISwingScoutUncachedImagedField (a copy of ISwingScoutImageField)
  This, too is a 1:1 copy of the original with adjusted references)
  
• SwingScoutUncachedImageField (a copy of SwingScoutImageField with some modifications)
  - adjusting the names to the corresponding classes with "Uncached"
  - changing setImageFromScout as follows:
  

    protected void setImageFromScout(String imageId, Object image) {
      if (image == null) {
        if (imageId != null) {
          // try to use uncached image
          image = getUncachedIconLocator().getImage(imageId);
          if (image == null) {
            // as fallback, use cached image
            image = getSwingEnvironment().getImage(imageId);
          }
        }
      }
      getSwingImageViewer().setImage(image);
    }

  
  - added the following code to the class:
  

    private SwingUncachedIconLocator m_uncachedIconLocator;
    protected SwingUncachedIconLocator getUncachedIconLocator() {
      if (m_uncachedIconLocator == null) {
        m_uncachedIconLocator = new SwingUncachedIconLocator(getSwingEnvironment().getScoutSession().getIconLocator());
      }
      return m_uncachedIconLocator;
    }

  
  
• SwingUncachedIconLocator (a copy of SwingIconLocator with some modifications)
  

    public Image getImage(String name) {
      if (name == null || AbstractIcons.Null.equals(name) || name.length() == 0) {
        return null;
      }
      Image img;
      synchronized (m_cacheLock) {
        //img = m_imagesByNameCache.get(name); // not using cache
        //if (img == null && !m_imagesByNameCache.containsKey(name)) { // not using cache
          img = createImageImpl(name);
          if (img == null) {
            img = autoCreateMissingImage(name);
          }
          //m_imagesByNameCache.put(name, img); // not using cache
          if (LOG.isDebugEnabled()) {
            LOG.debug("load image '" + name + "' as " + img);
          }
          if (img == null) {
            warnImageNotFound(name);
          }
        //} // not using cache
      }
      return img;
    }

  
  
• added the following block to plugin.xml
  

       <formField
             active="true"
             modelClass="com.bsiag.minicrm.client.ui.form.fields.ext.IUncachedImageField"
             name="Uncached Image Field"
             scope="default">
          <uiClass
                class="com.bsiag.minicrm.ui.swing.form.fields.ext.SwingScoutUncachedImageField">
          </uiClass>
       </formField>

  
  

• what is the recommended way to handle images that can change during the life time of the client? Use constantly changing imageIds (bearing the cost of an overblown cache)? Or is there a more elegant solution I fail to see?
  
• Instead of copying more than half a dozen files to emulate ImageField except for not using a cache in the icon locator, is there an easier way of changing the behaviour of a an existing FormField?
  
• how would I need to proceed to make the table column icon use the uncached icon locator (if there is no easier solution to my problem)?
  

The tutorial basically seems to read the image data and then put it in the icon cache from which it can be retrieved by the string id. So maybe it was designed to cache the icon and never change it again.

Have you tried reading the image data (= byte[]) by yourself and directly setting it into the ImageField by using the method setImage(Object)?

This does not work for images in a table, though, because the ImageField is not used there. For an ICell, you can only specify icons "by ID" and not "by data". IDs are then resolved using the SwingEnvironment's icon locator. So, if you override the method createIconLocator() and provide your own (non-caching) SwingIconLocator, you should be able to achieve the desired behavior. As far as I could see at a quick glance, the ImageField also retrieves the icon locator from the SwingEnvironment. If you try that our, please let us know if it worked.

Regarding your concern about having to copy so many files the create a custom widget: I admit that I did not try it out ( ), but I think in your case it would have to be sufficient to only register a new UncachedSwingScoutImageField class that extends SwingScoutImageField (for 'IImageField'). If I am correct, the most specific (i.e. greatest distance to IFormField) class "wins". Duplicating the model class (AbstractImageField) should not be necessary as you do not want to alter the model behavior.

(Note that this approach would then affect all ImageField!)

Does that already help your for your problem? If you think that a mechanism to invalidate the image cache is missing from Scout, maybe we should discuss it further.

• using my own, full blown custom UncachedImageField implementation (advantage: I can choose which fields are cached and which are uncached)
  
• extending SwingScoutImageField to use the non-caching locator (disadvantage: all ImageFields will be uncached)
  
• overwriting createIconLocator (disadvantage: all ImageFields and table icons will be uncached)
  
• using setImage method (advantage: I can choose which fields are cached and which are uncached)
  

• overwriting createIconLocator, with the disadvantage that all ImageFields and all table icons will be uncached)
  
• I suppose I could look at "cloning" all classes used for a TableField (or maybe the TablePage?) to allow for selective uncached icons in cells, but that may be a bit much effort even though it would probably teach me a lot about scout
  

• using setImage(byte[]) instead of setImageId(String) in the form solves the caching problem
  
• overwriting SwingEnvironment.createIconLocator() succesfully makes all images uncached (form and tables)
  
• I then removed all files mirroring the *ImageField classes and only kept my SwingScoutUncachedImageField and SwingUncachedIconLocator classes, I also removed the entry in plugin.xml for the new classes.
  I let SwingScoutUncachedImageField inherit from SwingScoutImageField
  

  public class SwingScoutUncachedImageField extends SwingScoutImageField {
    private SwingUncachedIconLocator m_uncachedIconLocator;
  
    protected SwingUncachedIconLocator getUncachedIconLocator() {
      if (m_uncachedIconLocator == null) {
        m_uncachedIconLocator = new SwingUncachedIconLocator(getSwingEnvironment().getScoutSession().getIconLocator());
      }
      return m_uncachedIconLocator;
    }
  
    @Override
    protected void setImageFromScout(String imageId, Object image) {
      if (image == null) {
        if (imageId != null) {
          // try to use uncached image
          image = getUncachedIconLocator().getImage(imageId);
          if (image == null) {
            // as fallback, use cached image
            image = getSwingEnvironment().getImage(imageId);
          }
        }
      }
      getSwingImageViewer().setImage(image);
    }

  
  and added the following entry to the plugin.xml
  

       <formField
             active="true"
             modelClass="org.eclipse.scout.rt.client.ui.form.fields.imagebox.IImageField"
             name="Uncached Image Field"
             scope="default">
          <uiClass
                class="com.bsiag.minicrm.ui.swing.form.fields.ext.SwingScoutUncachedImageField">
          </uiClass>
       </formField>

  
  
  This should make my new class the "most distant" for this interface but it seems that this does not work, the setImageFromScout() method was always called on SwingScoutImageField and not on my class. Removing the plugin entry doesn't make a difference.
  I don't know if you have any further ideas on this.
  

This should make my new class the "most distant" for this interface but it seems that this does not work, the setImageFromScout() method was always called on SwingScoutImageField and not on my class. Removing the plugin entry doesn't make a difference.
I don't know if you have any further ideas on this.

  @Override
  public ISwingScoutFormField<?> createFormField(JComponent parent, IFormField field) {
    if (field instanceof IImageField /* && add further conditions here */) {
      SwingScoutUncachedImageField ui = new SwingScoutUncachedImageField();
      ui.createField((IImageField) field, this);
      decorate(field, ui);
      return ui;
    }
    return super.createFormField(parent, field);
  }

Overall I think using the MD5 hash as imageId for the table cells and directly using the setImage() method on the form will be the most efficient way to deal with my requirement.

Hi, I am facing the same issue now. I would like to display image which will constantly change. but the image is cached. I am using rap client and swt client. do I need to modify SwtEnvironment to make it not cache image?

(...)
Unlike the FontRegistry, it is an error to replace images. As a result
there are no events that fire when values are changed in the registry

If I using MD5 hash as cache value, will the image cache be released? or it will keep building up again and again and eventually hit too many handle in windows or too many open file in linux?

The other possibility would be to not delegate the creation of IImageField UI objects to the FormFieldFactory, but build them yourself in your own SwingEnvironment:

  @Override
  public ISwingScoutFormField<?> createFormField(JComponent parent, IFormField field) {
    if (field instanceof IImageField /* && add further conditions here */) {
      SwingScoutUncachedImageField ui = new SwingScoutUncachedImageField();
      ui.createField((IImageField) field, this);
      decorate(field, ui);
      return ui;
    }
    return super.createFormField(parent, field);
  }

Urs Beeli wrote on Thu, 20 December 2012 04:47

Overall I think using the MD5 hash as imageId for the table cells and directly using the setImage() method on the form will be the most efficient way to deal with my requirement.

I like the idea of using the MD5 hash as a cache value. Looks promising! Thanks for sharing.