[udig-devel] SLD: How to combine different feature attributes for a Text

[tony.roth@xxxxxx]

Hi list,

I want to show a set of feature attributes (all Strings) as one label in the map next to the point/graphic. Like "1; London; 12" (number of item, name and a status). Since the user can toggle check boxes to switch on/off single values I can not store all information in one feature attribute. Instead of this I have n (currently 5) feature attributes for this. This is the way I thought it's the correct one:

 

---- code ----

// after each attribute except the last one a seperator like ";"

// textAttributes is a List of attributes the user wants to be shown

// Attributes is a enum with all attributes

_expression_[] expressions = new _expression_[textAttributes.size()*2-1];
      int i = 0;
      for (Attributes a : Attributes.values()){
       if (textAttributes.contains(a)){

// attribute _expression_ for the attribute
        _expression_ attributeExpression = FilterFactoryFinder.createFilterFactory().createAttributeExpression(a.name());

// literal _expression_ for the seperator
        LiteralExpression seperator = FilterFactoryFinder.createFilterFactory().createLiteralExpression(";");
        expressions[i++]=attributeExpression;
        if (i<expressions.length){
         expressions[i++]=seperator;
        }
       }
      }

// Filter to concatenate strings
      FilterFunction_strConcat concatFunction = new FilterFunction_strConcat();
      concatFunction.setArgs(expressions);

// create TextSymbolizer (fill and font are handled above... not interesting here)
      myStyleBuilder.createTextSymbolizer(fill, new Font[] {gtFont},null, concatFunction, placement, null));

---- code ----

My first problem was to find a possibility to concatenate strings. Since http://udig.refractions.net/docs/api-geotools/org/geotools/filter/function/FilterFunction_strConcat.html has a very poor javadoc explanation I just guessed that this function is the correct one.

 

What happend?

Independet of the number of attributes I want to show (2,3,4,5) only the first attribute combined with the first seperator (";") is drawn. So I got "London;" instead of "London;1;3". If I flip the order of attributes I get "1;" instead of "1;London;3". As I said only the first two expressions (one attribute, one literal) are included. Since these two are included I guess that the FilterFunction_strConcat is the correct way. Can someone help me with this?

I debuged it and the expressions array is build correct, has no null elements and all seems ok.

 

Thank you,

tony roth