Package org.ow2.authzforce.core.pdp.api.expression

Class ConstantExpression<V extends Value>

java.lang.Object

org.ow2.authzforce.core.pdp.api.expression.ConstantExpression<V>

Type Parameters:

V - concrete value type

All Implemented Interfaces:

Expression<V>

Direct Known Subclasses:

ConstantPrimitiveAttributeValueExpression, FunctionExpression

public abstract class ConstantExpression<V extends Value>
extends Object
implements Expression<V>

Expression wrapper for constant values - that do not depend on the evaluation context - to be used as Expressions, e.g. to be used as function argument. This is an alternative to Value extending Expression directly, which would break the Acyclic Dependency principle since Expression already has a reference to Value.

Field Summary

Fields

Modifier and Type	Field	Description
protected Optional<V>	alwaysPresentValue

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	ConstantExpression(Datatype<V> datatype, V v)	Creates instance of constant value expression

Method Summary

Modifier and Type	Method	Description
V	evaluate(EvaluationContext context)	Returns the value itself
Datatype<V>	getReturnType()	Gets the expected return type of the expression if evaluated.
Optional<V>	getValue()	Returns the constant underlying value (always present)
String	toString()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

alwaysPresentValue

protected final Optional<V extends Value> alwaysPresentValue

Constructor Detail

ConstantExpression

protected ConstantExpression(Datatype<V> datatype,
                             V v)
                      throws IllegalArgumentException

Creates instance of constant value expression

Parameters:

datatype - value datatype

v - constant value

Throws:

IllegalArgumentException - if datatype == null || v == null

Method Detail

getReturnType

public final Datatype<V> getReturnType()

Description copied from interface: Expression

Gets the expected return type of the expression if evaluated.

Specified by:

getReturnType in interface Expression<V extends Value>

Returns:

expression evaluation's return type

evaluate

public final V evaluate(EvaluationContext context)

Returns the value itself

Specified by:

evaluate in interface Expression<V extends Value>

Parameters:

context - the representation of the request

Returns:

the result of evaluation that may be a single value T (e.g. function result, AttributeValue, Condition, Match...) or bag of values (e.g. AttributeDesignator, AttributeSelector)

getValue

public final Optional<V> getValue()

Returns the constant underlying value (always present)

Specified by:

getValue in interface Expression<V extends Value>

Returns:

the constant value iff the expression has a static/fixed/constant value, else no present value. NB: Null is not considered/possible as a constant value for expressions.

toString

public String toString()

Overrides:

toString in class Object