org.vedantatree.expressionoasis

Class Compiler

java.lang.Object

org.vedantatree.expressionoasis.Compiler

public class Compiler
extends Object

This class performs the compilation operation in expression evaluation process.
It parses the expression using Parser, which returns it list of expression tokens as per rules specified with DefaultXMLGrammar. Compiler restructure these tokens in Reverse Polish Notation and then create the Expression Object's tree for all the tokens. TODO Precedence can be stored with Token itself during parsing process - probably not much benefit as precedence is not used repeatedly can we set operator, function etc values to token itself from parsing process? Give example of expression compilation and expression tree

Since:

3.1

Version:

1.0 Added support for caching of compiled expressions to improve performance for applications which repeatedly evaluate the same expressions against a different set of variables. This can be turned on or off in the XML config file. Modified to use collections that are not synchronized in order to reduce monitor conention. Still uses Stack, which wraps Vector, which is synchronized. Consider using another Stack implementation such as Google Collections., 1.1 Made Grammar Configurable from config.xml. Now Grammar class can be defined in config.xml and Compiler will pick it from there. It adds facility to use any custom Grammar object, 1.2

Author:

Mohit Gupta, Parmod Kamboj, Kris Marwood, Mohit Gupta

Constructor Summary

Constructors

Constructor and Description
Compiler() Constructs the Compiler with default DefaultXMLGrammar Instance
Compiler(Grammar grammar) Constructs the Compiler with specified DefaultXMLGrammar instance.

Method Summary

Modifier and Type	Method and Description
Expression	compile(String expression, ExpressionContext expressionContext, boolean validate) Builds a tree of Expression objects representing the expression.

Methods inherited from class java.lang.Object

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

Constructor Detail

Compiler

public Compiler()

Constructs the Compiler with default DefaultXMLGrammar Instance

Compiler

public Compiler(Grammar grammar)

Constructs the Compiler with specified DefaultXMLGrammar instance.

Parameters:

grammar - the grammar using which compiler will parse the expression

Throws:

IllegalArgumentException - if the grammar object is null

Method Detail

compile

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

Builds a tree of Expression objects representing the expression.

Parameters:

expression - the string representing the expression to build

expressionContext - the object which may contain contextual information for expressions

Returns:

the tree of expression objects

Throws:

ExpressionEngineException