Package org.geotools.filter.visitor

Class NullFilterVisitor

  • All Implemented Interfaces:
    ExpressionVisitor, FilterVisitor
    Direct Known Subclasses:
    ExtractBoundsFilterVisitor, TimeRangeVisitor
    public abstract class NullFilterVisitor
extends Object
implements FilterVisitor, ExpressionVisitor
    Abstract implementation of FilterVisitor simple returns the provided data.

    This class can be used as is as a placeholder that does nothing: 

    
 Integer one = (Integer) filter.accepts( NullFilterVisitor.NULL_VISITOR, 1 );
    The class can also be used as an alternative to DefaultFilterVisitor if you want to only walk part of the data structure: 
    
 FilterVisitor allFids = new NullFilterVisitor(){
     public Object visit( Id filter, Object data ) {
         if( data == null) return null;
         Set set = (Set) data;
         set.addAll(filter.getIDs());
         return set;
     }
 };
 Set set = (Set) myFilter.accept(allFids, new HashSet());
 Set set2 = (Set) myFilter.accept(allFids, null ); // set2 will be null
    The base class provides implementations for:
    • walking And, Or, and Not data structures, returning null at any point will exit early
    • a default implementation for every other construct that will return the provided data
    Author:
    Jody Garnett (Refractions Research)