org.vedantatree.expressionoasis

Class ExpressionEngine

java.lang.Object

org.vedantatree.expressionoasis.ExpressionEngine

public final class ExpressionEngine
extends Object

It is a Utility class for XpressionEngine Framework. It provides utility methods for accessing various functionalities of the Framework. A few points to consider -If any of the sub-expression is returning Type.ANY_TYPE, i.e. type will be decided at runtime. -If any of the sub-expression is returning Type.ANY_TYPE, the whole expression will return Type.ANY_TYPE -If expression contains XML expression, XML document 'URL' should be set as property to Context before executing the expression -In case of XML expression, it will always return the String value as it does not have any way to identify the required type of the value - To override all above, currently we are getting only string type value from XML expressions

Since:

3.1

Version:

1.0 Added the ability to extract the variable names from an expression., 1.1 Exposed Grammar through API. Anyone can use the Grammar to get any metadata or to add specific metadata like function's definition, 1.2

Author:

Mohit Gupta, Parmod Kamboj, Kris Marwood, Mohit Gupta

Method Summary

Modifier and Type	Method and Description
static Expression	compileExpression(String expression, ExpressionContext expressionContext, boolean validate) Compiles the expression string and prepares the expression tree with relevant Expression's objects.
static Object	evaluate(String expression, ExpressionContext expressionContext) Evaluates the expression and returns the result
static Grammar	getGrammar()
static Set<String>	getVariableNames(String expression) Retrieves a set of variable names contained within the specified expression string
static void	main(String[] args)

Methods inherited from class java.lang.Object

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

Method Detail

getGrammar

public static Grammar getGrammar()

evaluate

public static Object evaluate(String expression,
                              ExpressionContext expressionContext)
                       throws ExpressionEngineException

Evaluates the expression and returns the result

Parameters:

expression - the expression to evaluate

expressionContext - the object contains the contextual information, which may be required for expression evaluation. It may be like an Java Bean in case of property expression

Returns:

the result of expression

Throws:

ExpressionEngineException - if unable to parse the expression

compileExpression

public static Expression compileExpression(String expression,
                                           ExpressionContext expressionContext,
                                           boolean validate)
                                    throws ExpressionEngineException

Compiles the expression string and prepares the expression tree with relevant Expression's objects.

Parameters:

expression - the expression to compile

expressionContext - the object contains the contextual information, which may be required for expression evaluation. It may be like an Java Bean in case of property expression

validate - true if the operands should be validated

Returns:

compiled Expression object. It is actually a tree of Expression Objects

Throws:

ExpressionEngineException - if unable to compile the expression

getVariableNames

public static Set<String> getVariableNames(String expression)
                                    throws ExpressionEngineException

Retrieves a set of variable names contained within the specified expression string

Parameters:

expression - the expression to extract the variable names for

Returns:

a set of variable names contained within the specified expression string

Throws:

ExpressionEngineException

main

public static void main(String[] args)
                 throws ExpressionEngineException

Throws:

ExpressionEngineException