issrg.pba.rbac.xmlpolicy.ifstatement
Class OperationNode

java.lang.Object
  issrg.pba.rbac.xmlpolicy.PolicyXMLNode
      issrg.pba.rbac.xmlpolicy.ifstatement.TermNode
          issrg.pba.rbac.xmlpolicy.ifstatement.OperationNode

All Implemented Interfaces:

Term

Direct Known Subclasses:

AndNode, EqNode, GeNode, GtNode, LeNode, LtNode, NotNode, OperatorNode, OrNode, PresentNode, SubstringsNode

public class OperationNode
extends TermNode

This is an abstract class which is a base to other operations. The sub-classes would only need to have a valid constructor, so the XMLParser will be able to instantiate a working copy of it, and perhaps a static registration method to update the collection of interpreters.

This class maintains a registry of Interpreters for each type of operation. During evaluation time an Interpreter will be found in the registry for the required type of operation and it will be used to perform the evaluation. If no Interpreter can be found for the specific set of Terms, EvaluationException occurs.

See Also:

Interpreter

Field Summary

protected Interpreter	interpreter
protected java.lang.String	type

Fields inherited from class issrg.pba.rbac.xmlpolicy.ifstatement.TermNode

maxOperand, minOperand, terms

Fields inherited from class issrg.pba.rbac.xmlpolicy.PolicyXMLNode

attributes, children, name, nodeStr

Constructor Summary

protected	OperationNode()
	OperationNode(java.lang.String nodeName, org.xml.sax.Attributes attrs, int maxOperandCount, int minOperandCount) This constructor builds an OperationNode given the name and the attributes of the XML element, and the acceptable numbers of operands.

Method Summary

void	construct() The method builds a usual TermNode and then checks if an interpreter can be found that would agree to interpret the relevant terms (children nodes) and deliver a definite result.
java.lang.Object	evaluate(Environment env) This method evaluates the expression given the environment.
java.lang.String	getType() This method returns the type of the value this term returns.

Methods inherited from class issrg.pba.rbac.xmlpolicy.ifstatement.TermNode

getInterpretersForNode, registerInterpreterForNode

Methods inherited from class issrg.pba.rbac.xmlpolicy.PolicyXMLNode

addChild, addString, getAttributes, getChildren, getName, getString, toString, toXML, toXML

Methods inherited from class java.lang.Object

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

Field Detail

type

protected java.lang.String type

interpreter

protected Interpreter interpreter

Constructor Detail

OperationNode

protected OperationNode()

OperationNode

public OperationNode(java.lang.String nodeName,
                     org.xml.sax.Attributes attrs,
                     int maxOperandCount,
                     int minOperandCount)

This constructor builds an OperationNode given the name and the attributes of the XML element, and the acceptable numbers of operands.

Parameters:

nodeName - - the name of the XML element this OperationNode represents

attrs - - the attributes of this XML element

maxOperandCount - - the maximum acceptable number of operands; if "-1", any number of operands is acceptable

minOperandCount - - the minimum acceptable number of operands

Method Detail

construct

public void construct()
               throws PolicyParsingException

The method builds a usual TermNode and then checks if an interpreter can be found that would agree to interpret the relevant terms (children nodes) and deliver a definite result. If no such interpreter is found, a PolicyParsingException is thrown; otherwise, the interpreter will be used by the evaluate method, and the result type reported by the canEvaluate method of the interpreter will be returned by the getType method.

Overrides:

construct in class TermNode

Throws:

PolicyParsingException - if one of the above-stated conditions is violated

getType

public java.lang.String getType()

Description copied from interface: Term

This method returns the type of the value this term returns. The types are defined by convention of the developers and RBAC policy administrators.

Returns:

a case-sensitive type name as calculated at run-time

evaluate

public java.lang.Object evaluate(Environment env)
                          throws EvaluationException

This method evaluates the expression given the environment. It uses the Interpreter found during the call to construct();

Parameters:

env - - the Environment with the variables in it

Returns:

the Interpreter-specific object, guaranteed to be of type returned by getType()

Throws:

EvaluationException, - if there was a problem evaluating the expression

EvaluationException - if the term cannot be evaluated