org.vedantatree.expressionoasis.expressions

Interface Expression

All Known Implementing Classes:

AddExpression, AndExpression, ArgumentExpression, ArrayIndexExpression, BinaryOperatorExpression, BooleanExpression, BWAndExpression, BWComplementExpression, BWOrExpression, BWSignedLeftShiftExpression, BWSignedRightShiftExpression, BWUnsignedRightShiftExpression, BWXorExpression, ConditionTernaryExpression, ContainsExpression, DecimalExpression, DivideExpression, EndsWithExpression, EQExpression, FunctionExpression, GTEExpression, GTExpression, IdentifierExpression, LTEExpression, LTExpression, MinusExpression, MulExpression, MultiplyExpression, NEExpression, NotExpression, NullExpression, NumericExpression, OrExpression, ParanthesisExpression, PlusExpression, PropertyExpression, RemainderExpression, ResultTernaryExpression, StartsWithExpression, StringExpression, SubtractExpression, SumExpression, UnaryOperatorExpression, UnaryPropertyExpression

public interface Expression

This class represents the executable structure of an expression. Parser parse the expression and break it into individual expression tokens. This token list is feed to compiler for creating the executable structure of expressions using objects of this class. Compiler create relevant expression object (of this class) for every token and creates a relative expression chain as operands or operators. Final outcome of Compiler is a single top level expression which contains all expression in hierarchy. So the final expression can be an atomic Expression class or an Expression having a large tree of children expressions with it. TODO improve tostring to represent actual expression

Version:

1.0 Modified to support visitor design pattern., 1.1

Author:

Mohit Gupta, Parmod Kamboj, Kris Marwood

Method Summary

Modifier and Type	Method and Description
void	accept(ExpressionVisitor visitor) Implements visitor pattern.
Type	getReturnType() Gets the return type of the expression.
ValueObject	getValue() Executes and returns the value of this expression.
void	initialize(ExpressionContext expressionContext, Object parameters, boolean validate) This is used to initialize the expression.
void	uninitialize(ExpressionContext expressionContext) This is used to un-initialize the expression, so that expression can be reused.

Method Detail

getValue

ValueObject getValue()
              throws ExpressionEngineException

Executes and returns the value of this expression. If expression is not at node level, it will further evaluate its related expression which may represents operands or operators and return the final outcome.

Returns:

the value of expression (after expression evaluation)

Throws:

ExpressionEngineException - if there is any problem during execution

getReturnType

Type getReturnType()
            throws ExpressionEngineException

Gets the return type of the expression.

Returns:

the type of expression

Throws:

ExpressionEngineException - If there is any problem during execution

initialize

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

This is used to initialize the 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

uninitialize

void uninitialize(ExpressionContext expressionContext)

This is used to un-initialize the expression, so that expression can be reused.

Parameters:

expressionContext - contextual information, may help in un-initialization

accept

void accept(ExpressionVisitor visitor)

Implements visitor pattern.

Parameters:

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