issrg.pba.rbac.xmlpolicy.ifstatement
Class StringInterpreter

java.lang.Object
  issrg.pba.rbac.xmlpolicy.ifstatement.StringInterpreter

All Implemented Interfaces:

Interpreter

public class StringInterpreter
extends java.lang.Object
implements Interpreter

This is the interpreter for comparisons of strings in the IF-statements. It provides the following semantics:

• EQ is a case-sensitive test for equality of strings two,
• GE, GT, LE, LT - case-sensitive test of vocabulary order of two strings ("greater" meaning "later in vocabulary order", "less" meaning "earlier in vocabulary order")
• Substrings - checking if the first string is met anywhere in the second string (case sensitive).

Author:

A.Otenko

Field Summary

static int	EQ_MODE
static int	GE_MODE
static int	GT_MODE
static int	LE_MODE
static int	LT_MODE
protected int	mode
static int	SUBSTRINGS_MODE

Constructor Summary

protected	StringInterpreter()
protected	StringInterpreter(int mode) This is the constructor used to build the interpreter for different types of comparison operation: an interpreter for Substrings, GE, LE, GT, LT and EQ correspondingly.

Method Summary

java.lang.String	canEvaluate(Term[] t) This method tells whether this interpreter can evaluate the expression, which is only if there are only two Terms, and both are of type Types.STRING_TYPE.
java.lang.Object	evaluate(Environment env, Term[] t) This method evaluates the comparison expression, depending on the mode it was given at construction time.
static void	register() Call this method to register the IntegerInterpreter with the relevant expression nodes: EqNode, GeNode, GtNode, LeNode, LtNode, SubstringsNode.

Methods inherited from class java.lang.Object

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

Field Detail

mode

protected int mode

EQ_MODE

public static final int EQ_MODE

See Also:

Constant Field Values

GE_MODE

public static final int GE_MODE

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Constant Field Values

LE_MODE

public static final int LE_MODE

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Constant Field Values

GT_MODE

public static final int GT_MODE

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Constant Field Values

LT_MODE

public static final int LT_MODE

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Constant Field Values

SUBSTRINGS_MODE

public static final int SUBSTRINGS_MODE

See Also:

Constant Field Values

Constructor Detail

StringInterpreter

protected StringInterpreter()

StringInterpreter

protected StringInterpreter(int mode)

This is the constructor used to build the interpreter for different types of comparison operation: an interpreter for Substrings, GE, LE, GT, LT and EQ correspondingly. The evaluate method will return the comparison result corresponding to this mode.

Parameters:

mode - stands for the mode of operation; it can be one of SUBSTRINGS_MODE, EQ_MODE, GE_MODE, LE_MODE, GT_MODE or LT_MODE

Method Detail

register

public static void register()

Call this method to register the IntegerInterpreter with the relevant expression nodes: EqNode, GeNode, GtNode, LeNode, LtNode, SubstringsNode. The interpreter provides the conventional semantics of vocabulary order of strings for those operations, as explained above.

canEvaluate

public java.lang.String canEvaluate(Term[] t)

This method tells whether this interpreter can evaluate the expression, which is only if there are only two Terms, and both are of type Types.STRING_TYPE.

Specified by:

canEvaluate in interface Interpreter

Parameters:

t - - the array of Terms to be evaluated

Returns:

Types.BOOLEAN_TYPE, if the expression can be evaluated; null otherwise

evaluate

public java.lang.Object evaluate(Environment env,
                                 Term[] t)
                          throws EvaluationException

This method evaluates the comparison expression, depending on the mode it was given at construction time. If the expression can be evaluated, it returns a java.lang.Boolean object; otherwise a EvaluationException is thrown.

Specified by:

evaluate in interface Interpreter

Parameters:

env - - the Environment in which the evaluation occurs

t - - the array of Terms to be evaluated; should contain two and only two Terms, each of type Types.STRING_TYPE

Returns:

java.lang.Boolean object that contains the boolean result of evaluation, as determined by the mode provided at construction time

Throws:

EvaluationException