org.geotools.filter
Class ConstantExpression

Object
  ConstantExpression

All Implemented Interfaces:

Cloneable, ExpressionType, LiteralExpression, Expression, Literal

Direct Known Subclasses:

OverlapBehavior

public class ConstantExpression
extends Object
implements LiteralExpression, Cloneable

The Expression class is not immutable!

However we do have a need for immutable literal expressions when defining our API for SLD, and any other standards based on Expression.

Author:

Jody Garnett, Refractions Research

Field Summary

static ConstantExpression	BLACK
static ConstantExpression	NULL
static ConstantExpression	ONE
static ConstantExpression	TWO
static ConstantExpression	UNNAMED
static ConstantExpression	ZERO

Fields inherited from interface ExpressionType

ATTRIBUTE, ATTRIBUTE_DOUBLE, ATTRIBUTE_GEOMETRY, ATTRIBUTE_INTEGER, ATTRIBUTE_STRING, ATTRIBUTE_UNDECLARED, FUNCTION, LITERAL_DOUBLE, LITERAL_GEOMETRY, LITERAL_INTEGER, LITERAL_LONG, LITERAL_STRING, LITERAL_UNDECLARED, MATH_ADD, MATH_DIVIDE, MATH_MULTIPLY, MATH_SUBTRACT

Fields inherited from interface Expression

NIL

Constructor Summary

protected	ConstantExpression(Object value)
protected	ConstantExpression(short type, Object value)

Method Summary

Object	accept(ExpressionVisitor visitor, Object extraData) Accepts a visitor.
void	accept(FilterVisitor visitor) Deprecated. use accept(ExpressionVisitor, Object).
protected Object	clone()
static ConstantExpression	color(Color color) Encode provided color as a String
static ConstantExpression	constant(double number)
static ConstantExpression	constant(int number)
static ConstantExpression	constant(Object value)
boolean	equals(Object obj)
Object	evaluate(Object object) Evaluates the given expression based on the content of the given object.
<T> T	evaluate(Object object, Class<T> context) Evaluates the given expressoin based on the content of the given object and the context type.
Object	evaluate(SimpleFeature feature) Evaluates the expression against an instance of Feature.
Object	getLiteral() Deprecated. use getValue()
short	getType() Returns the literal type.
Object	getValue() Returns the constant value held by this object.
Object	getValue(SimpleFeature feature) Deprecated. use #evaluate(Feature)
int	hashCode()
void	setLiteral(Object literal) Deprecated. use setValue(Object)
void	setValue(Object constant)
String	toString()

Methods inherited from class Object

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

Field Detail

NULL

public static final ConstantExpression NULL

BLACK

public static final ConstantExpression BLACK

ZERO

public static final ConstantExpression ZERO

ONE

public static final ConstantExpression ONE

TWO

public static final ConstantExpression TWO

UNNAMED

public static final ConstantExpression UNNAMED

Constructor Detail

ConstantExpression

protected ConstantExpression(Object value)

ConstantExpression

protected ConstantExpression(short type,
                             Object value)

Method Detail

setLiteral

public final void setLiteral(Object literal)
                      throws IllegalFilterException

Deprecated. use setValue(Object)

Description copied from interface: LiteralExpression

Sets the literal.

Specified by:

setLiteral in interface LiteralExpression

Parameters:

literal - The literal to store inside this expression.

Throws:

IllegalFilterException - This literal type is not in scope.

getValue

public final Object getValue(SimpleFeature feature)

Deprecated. use #evaluate(Feature)

Description copied from interface: LiteralExpression

Gets the value of this literal.

Specified by:

getValue in interface LiteralExpression

Parameters:

feature - Required by the interface but not used.

Returns:

the literal held by this expression. Ignores the passed in feature.

evaluate

public Object evaluate(SimpleFeature feature)

Description copied from interface: Expression

Evaluates the expression against an instance of Feature.

Parameters:

feature - The feature being evaluated.

Returns:

The result.

evaluate

public Object evaluate(Object object)

Description copied from interface: Expression

Evaluates the given expression based on the content of the given object.

Specified by:

evaluate in interface Expression

evaluate

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

Description copied from interface: Expression

Evaluates the given expressoin based on the content of the given object and the context type.

The context parameter is used to control the type of the result of the expression. A particular expression may not be able to evaluate to an instance of context. Therefore to be safe calling code should do a null check on the return value of this method, and call Expression.evaluate(Object) if neccessary. Example:

  Object input = ...;
  String result = expression.evaluate( input, String.class );
  if ( result == null ) {
     result = expression.evalute( input ).toString();
  }
  ...
 

Implementations that can not return a result as an instance of context should return null.

Specified by:

evaluate in interface Expression

Type Parameters:

T - The type of the returned object.

Parameters:

object - 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.

getValue

public Object getValue()

Description copied from interface: Literal

Returns the constant value held by this object.

Specified by:

getValue in interface Literal

setValue

public void setValue(Object constant)

getType

public short getType()

Description copied from interface: LiteralExpression

Returns the literal type.

Specified by:

getType in interface LiteralExpression

Returns:

the short representation of the literal expression type.

getLiteral

public final Object getLiteral()

Deprecated. use getValue()

Description copied from interface: LiteralExpression

Retrieves the literal of this expression.

Specified by:

getLiteral in interface LiteralExpression

Returns:

the literal held by this expression.

accept

public void accept(FilterVisitor visitor)

Deprecated. use accept(ExpressionVisitor, Object).

Description copied from interface: Expression

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.

Parameters:

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

accept

public Object accept(ExpressionVisitor visitor,
                     Object extraData)

Description copied from interface: Expression

Accepts a visitor. Subclasses must implement with a method whose content is the following:

return visitor.visit(this, extraData);

Specified by:

accept in interface Expression

clone

protected Object clone()
                throws CloneNotSupportedException

Overrides:

clone in class Object

Throws:

CloneNotSupportedException

equals

public boolean equals(Object obj)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

toString

public String toString()

Overrides:

toString in class Object

color

public static ConstantExpression color(Color color)

Encode provided color as a String

constant

public static ConstantExpression constant(double number)

constant

public static ConstantExpression constant(int number)

constant

public static ConstantExpression constant(Object value)