org.vedantatree.expressionoasis.expressions

Class NullExpression

java.lang.Object

org.vedantatree.expressionoasis.expressions.NullExpression

All Implemented Interfaces:

Expression

public class NullExpression
extends Object
implements Expression

This class expression is used to make the null value expression. It gives the null value. Based on Numeric Expression. TODO: should we create a special null type in Type class rather than using Type.createType("java.lang.Object")? Currently don't have that option as the code for Type class is not yet available.

Version:

1.0

Author:

Kris Marwood

Constructor Summary

Constructors

Constructor and Description
NullExpression()

Method Summary

Modifier and Type	Method and Description
void	accept(ExpressionVisitor visitor) Allows an expression visitor to visit this expression and it's sub-expressions (implements Visitor design pattern).
Type	getReturnType() Returns the long type.
ValueObject	getValue() Gets the value object for numeric value.
void	initialize(ExpressionContext expressionContext, Object parameters, boolean validate) Initializes the numeric value object.
String	toString()
void	uninitialize(ExpressionContext expressionContext) Uninitaizes the expression

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

NullExpression

public NullExpression()

Method Detail

getValue

public ValueObject getValue()
                     throws ExpressionEngineException

Gets the value object for numeric value.

Specified by:

getValue in interface Expression

Returns:

the value of expression (after expression evaluation)

Throws:

ExpressionEngineException - if there is any problem during execution

See Also:

Expression.getValue()

getReturnType

public Type getReturnType()
                   throws ExpressionEngineException

Returns the long type.

Specified by:

getReturnType in interface Expression

Returns:

the type of expression

Throws:

ExpressionEngineException - If there is any problem during execution

See Also:

Expression.getReturnType()

initialize

public void initialize(ExpressionContext expressionContext,
                       Object parameters,
                       boolean validate)
                throws ExpressionEngineException

Initializes the numeric value object.

Specified by:

initialize in interface Expression

Parameters:

expressionContext - contextual information, may help in initialization

parameters - for example, sub expressions and identifiers

Throws:

ExpressionEngineException - if there is any problem during execution

See Also:

org.vedantatree.expressionoasis.expressions.Expression#initialize(org.vedantatree.expressionoasis.ExpressionContext, java.lang.Object)

uninitialize

public void uninitialize(ExpressionContext expressionContext)

Uninitaizes the expression

Specified by:

uninitialize in interface Expression

Parameters:

expressionContext - contextual information, may help in un-initialization

See Also:

Expression.uninitialize(org.vedantatree.expressionoasis.ExpressionContext)

toString

public String toString()

Overrides:

toString in class Object

See Also:

Object.toString()

accept

public void accept(ExpressionVisitor visitor)

Allows an expression visitor to visit this expression and it's sub-expressions (implements Visitor design pattern).

Specified by:

accept in interface Expression

Parameters:

visitor - a visitor object that this expression must visit when accept is called.

See Also:

org.vedantatree.expressionoasis.expressions.Expression#accept(org.vedantatree.expressionoasis.ExpressionVisitor)