org.opengis.filter.expression

Interface InternalFunction

All Superinterfaces:

Expression, Function

All Known Implementing Classes:

InternalVolatileFunction

public interface InternalFunction
extends Function

Special Function type indicating that that the function is to be executed exclusively at run-time, and does not participate in the SPI (Service Provider Interface) lookup mechanism (i.e. cannot be created using a FilterFactory).

This is a (non OGC Filter compatible) extension point to the Filter API to allow for anonymous inner classes to be used in filters.

The additional duplicate(Expression...) method allows for implementations to return a new instance of the function for the given set of arguments.

Usage example:

  
  InternalFunction function = new InternalFunction(){
      public String getName(){ return "MyFunction";}
      public FunctionName getFunctionName(){ return new FunctionNameImpl(getName(), 0);}
      public List getParameters(){ return Collections.emptyList(); }
      public Literal getFallbackValue() { return null; }

      public Object evaluate(Object object){
        return determineRuntimeFunctionValue(object);
      }
      public InternalFunction duplicate(Expression... parameters){
        return this;
      }
  }

  FilterFactory ff = ..
  Filter filter = ff.equals(ff.literal(Boolean.TRUE), function);
 
 

Since:

9.0

Field Summary

Fields inherited from interface Expression

NIL

Method Summary

Modifier and Type	Method and Description
InternalFunction	duplicate(Expression... parameters) Factory method to return a new instance of its own kind that works on the given parameters.

Methods inherited from interface Function

getFallbackValue, getFunctionName, getName, getParameters

Methods inherited from interface Expression

accept, evaluate, evaluate

Method Detail

duplicate

InternalFunction duplicate(Expression... parameters)

Factory method to return a new instance of its own kind that works on the given parameters.

This is so because InternalFunctions do not participate on the standard SPI lookup mechanism and hence they can't be created by FilterFactory, yet on occasion a new copy might be needed, such as for duplicating filter visitors.

Note however implementations are free to return this if the actual function instance does not work with Expression as parameters.

Parameters:

parameters - the parameters the returned InternalFunction works on

Returns:

a new instance of the same kind of InternalFunction that works on the given parameters