situation:
The features of a point layer are symbolized with external graphics. All elements are presented to the user in a table and if he selectes one or more in this table the items shall be highlighted in the map. The SLD specification defines that a graphic either contains a mark or an external graphic, therefore it's not possible to surround the external graphic with a red square or something like that: I need another external grahpic.
To realize this my features have the featureattribute 'selected' and I generate a bunch of sld rulez: For each category of my items and for {selected;unselected} I generate a rule with a certain external graphic. (The categories define the symbol like windmill or tower)
If the user selects one or more items of the table this happens:
public void setSelection(List<Integer> selectedItems){
try {
FeatureStore fs = layer.getResource(FeatureStore.class, null);
// deselect all: setting the dedictated attribute type to UNSELECTED (static variable)
// this happens since we don't know which of the elements are selected at the moment
fs.modifyFeatures(selectionAttributeType, UNSELECTED, Filter.NONE);
FilterFactory filterFactory = FilterFactoryFinder.createFilterFactory();
// set the selected ones
for (Integer id:selectedItems){
AttributeExpression attributeExpression = filterFactory.createAttributeExpression(IDAttributeName);
LiteralExpression literalExpression = filterFactory.createLiteralExpression(id);
CompareFilter compareFilter = filterFactory.createCompareFilter(FilterType.COMPARE_EQUALS);
compareFilter.addLeftValue(attributeExpression);
compareFilter.addRightValue(literalExpression);
// this sets the filtered features to SELECTED
fs.modifyFeatures(selectionAttributeType, SELECTED, compareFilter);
}
} catch (Exception e) {
// ...
}
}
It works... somehow .. but not the way I wanted:
The renderer starts and on the first modifyFeatures comand (the deselection) all items are rendered. This takes about 14 seconds (on a pentium 4) with just four features in the layer. And only the graphics / symbols are rendered, the labels below the symbols are destroyed and I have to update the layer.
Another way could be to check which features switch >from selected to not selected and just modify these in the first step but with hundreds or more featuers this also takes a while.
Is this approach to be doomed and / or crap?
What is the best way to realize a kind of highlight features in the map with external graphics?
tony roth
