org.deegree.filter
Interface Expression

All Known Implementing Classes:

Add, Categorize, ChangeCase, Concatenate, Div, FormatDate, FormatNumber, Function, Interpolate, IsCurve, IsPoint, IsSurface, Literal, Mul, PropertyName, Recode, StringLength, StringPosition, Sub, Substring, Trim

public interface Expression

An Expression describes a rule to obtain a value that may be derived from the properties of a MatchableObject.

Note that the objects returned by evaluate(MatchableObject) is an Object[], as an expression may evaluate to multiple values, e.g. a PropertyName that targets a multi property of a feature. The values in the array always have one of the following classes:

• String
• Number
• Date
• DateTime
• Time
• Geometry

NOTE: Values in the returned array may also be null.

Version:

$Revision:$, $Date:$

Author:

Markus Schneider , last edited by: $Author:$

Nested Class Summary

static class

Expression.Type Convenience enum type for discriminating the different expression types.

Method Summary

Object[]	evaluate(MatchableObject obj) Determines the values of the expression for the given MatchableObject.
Expression[]	getParams() Returns the expression's paramters.
Expression.Type	getType() Returns the type of expression.
String	toString(String indent)

Method Detail

getType

Expression.Type getType()

Returns the type of expression. Use this to safely determine the subtype of Expression.

Returns:

type of expression

evaluate

Object[] evaluate(MatchableObject obj)
                  throws FilterEvaluationException

Determines the values of the expression for the given MatchableObject.

Note that this returns an Object[], as an expression may evaluate to multiple values, e.g. a PropertyName that targets a multi property of a feature.

Parameters:

obj - object that the expression is evaluated upon

Returns:

the values of the expression, may be empty (and even contain null values), but never null

Throws:

FilterEvaluationException

getParams

Expression[] getParams()

Returns the expression's paramters.

Returns:

the parameters of the expression

toString

String toString(String indent)