org.geotools.filter

Class LiteralExpressionImpl

Object

ExpressionAbstract

DefaultExpression

LiteralExpressionImpl

All Implemented Interfaces:

Expression, Literal

public class LiteralExpressionImpl
extends DefaultExpression
implements Literal

Defines an expression that holds a literal for return.

Author:

Rob Hranac, Vision for New York

Field Summary

Fields inherited from interface Expression

NIL

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	LiteralExpressionImpl() Constructor with literal.
protected	LiteralExpressionImpl(double value) Constructor with literal.
protected	LiteralExpressionImpl(int value) Constructor with literal.
protected	LiteralExpressionImpl(long value)
	LiteralExpressionImpl(Object literal) Constructor with literal.
protected	LiteralExpressionImpl(String value) Constructor with literal.

Method Summary

Modifier and Type	Method and Description
Object	accept(ExpressionVisitor visitor, Object extraData) Used by FilterVisitors to perform some action on this filter instance.
boolean	equals(Object obj) Compares this filter to the specified object.
Object	evaluate(Object feature) Subclass should override, default implementation returns null.
<T> T	evaluate(Object feature, Class<T> context) Default implementation delegates handling of context conversion to Converters utility class.
Object	getValue() Retrieves the literal of this expression.
int	hashCode() Override of hashCode method.
void	setValue(Object literal) Sets the literal.
String	toString() Return this filter as a string.

Methods inherited from class DefaultExpression

isAttributeExpression, isExpression, isFunctionExpression, isGeometryExpression, isLiteralExpression, isMathExpression

Methods inherited from class Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

LiteralExpressionImpl

protected LiteralExpressionImpl()

Constructor with literal.

LiteralExpressionImpl

public LiteralExpressionImpl(Object literal)
                      throws IllegalFilterException

Constructor with literal.

Parameters:

literal - The literal to store inside this expression.

Throws:

IllegalFilterException - This literal type is not in scope.

LiteralExpressionImpl

protected LiteralExpressionImpl(int value)

Constructor with literal. This alternative constructor is a convinience one for integers an Integer object will be constructed, and no IllegalFilterException can ever be thrown.

Parameters:

value - The integer to store inside this expression.

LiteralExpressionImpl

protected LiteralExpressionImpl(long value)

LiteralExpressionImpl

protected LiteralExpressionImpl(double value)

Constructor with literal. This alternative constructor is a convinience one for doubles an Double object will be constructed, and no IllegalFilterException can ever be thrown.

Parameters:

value - The double to store inside this expression.

LiteralExpressionImpl

protected LiteralExpressionImpl(String value)

Constructor with literal. This alternative constructor is a convinience one for doubles an Double object will be constructed, and no IllegalFilterException can ever be thrown.

Parameters:

value - The double to store inside this expression.

Method Detail

getValue

public Object getValue()

Retrieves the literal of this expression.

Specified by:

getValue in interface Literal

Returns:

the literal held by this expression.

setValue

public final void setValue(Object literal)

Sets the literal.

Parameters:

literal - The literal to store inside this expression.

Throws:

IllegalFilterException - This literal type is not in scope.

evaluate

public Object evaluate(Object feature)

Description copied from class: ExpressionAbstract

Subclass should override, default implementation returns null.

Specified by:

evaluate in interface Expression

Overrides:

evaluate in class ExpressionAbstract

Returns:

default implementation returns null

evaluate

public <T> T evaluate(Object feature,
                      Class<T> context)

Description copied from class: ExpressionAbstract

Default implementation delegates handling of context conversion to Converters utility class.

Subclasses are expected to make use of the Converters utility class (as the easiest way to provide value morphing in conformance with the Filter specification).

Specified by:

evaluate in interface Expression

Overrides:

evaluate in class ExpressionAbstract

Type Parameters:

T - The type of the returned object.

Parameters:

feature - The object to evaluate the expression against.

context - The type of the resulting value of the expression.

Returns:

Evaluates the given expression based on the content of the given object an an instance of context.

toString

public String toString()

Return this filter as a string.

Overrides:

toString in class Object

Returns:

String representation of this geometry filter.

equals

public boolean equals(Object obj)

Compares this filter to the specified object. Returns true if the passed in object is the same as this expression. Checks to make sure the expression types are the same as well as the literals.

Overrides:

equals in class Object

Parameters:

obj - - the object to compare this ExpressionLiteral against.

Returns:

true if specified object is equal to this expression; false otherwise.

TODO:

REVISIT: missmatched types now considered not equal. This may be a problem when comparing Doubles and Integers

hashCode

public int hashCode()

Override of hashCode method.

Overrides:

hashCode in class Object

Returns:

the hash code for this literal expression

accept

public Object accept(ExpressionVisitor visitor,
                     Object extraData)

Used by FilterVisitors to perform some action on this filter instance. Typicaly used by Filter decoders, but may also be used by any thing which needs infomration from filter structure. Implementations should always call: visitor.visit(this); It is importatant that this is not left to a parent class unless the parents API is identical.

Specified by:

accept in interface Expression

Parameters:

visitor - The visitor which requires access to this filter, the method must call visitor.visit(this);