issrg.pba.rbac.xmlpolicy.ifstatement
Class ConstantNode

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

All Implemented Interfaces:

Term

public class ConstantNode
extends TermNode

This is the class that represents a Constant node and evaluates the contant specified in the policy XML.

If the policy contains the constant of type for which there is no constructor provided by the AEF (not registered with the Types), an EvaluationException will occur at construction-time.

Author:

A.Otenko

Field Summary

static java.lang.String	CONSTANT_NODE This is the name of the node that represents the Constant - a static value specified in the policy.
protected java.lang.String	type
protected java.lang.Object	value

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	ConstantNode()
	ConstantNode(XMLPolicyParser p, org.xml.sax.Attributes attr) This constructor builds an ConstantNode, given a XMLPolicyParser and the set of attributes of this XML element.

Method Summary

java.lang.Object	evaluate(Environment env) This method returns the value of the constant evaluated at construction time.
java.lang.String	getType() This method returns the Type of the constant as determined at construction time.
static void	register() This method should be called to register the node with the XML Parser

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

construct, 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

CONSTANT_NODE

public static final java.lang.String CONSTANT_NODE

This is the name of the node that represents the Constant - a static value specified in the policy.

See Also:

Constant Field Values

type

protected java.lang.String type

value

protected java.lang.Object value

Constructor Detail

ConstantNode

protected ConstantNode()

ConstantNode

public ConstantNode(XMLPolicyParser p,
                    org.xml.sax.Attributes attr)
             throws EvaluationException,
                    PolicyParsingException

This constructor builds an ConstantNode, given a XMLPolicyParser and the set of attributes of this XML element. It expects that a issrg.pba.rbac.xmlpolicy.XMLTags.TYPE_ATTRIBUTE and issrg.pba.rbac.xmlpolicy.XMLTags.VALUE_ATTRIBUTE ("Type" and "Value") are present in this XML element. The value is converted from string into a Java object using the Types.construct() method, so the type of the value must be registered there.

Parameters:

p - - the XMLPolicyParser that builds this ConstantNode

attr - - the attributes of this XML element

Throws:

EvaluationException, - if the value could not be decoded using available types

EvaluationException

PolicyParsingException

See Also:

Types.construct(java.lang.String, java.lang.String)

Method Detail

register

public static void register()

This method should be called to register the node with the XML Parser

getType

public java.lang.String getType()

This method returns the Type of the constant as determined at construction time.

Returns:

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

evaluate

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

This method returns the value of the constant evaluated at construction time. It doesn't actually throw EvaluationExceptions, but the clause is kept for subclasses, if there will be any.

Parameters:

env - is the execution environment

Returns:

an object representing the result

Throws:

EvaluationException - if the term cannot be evaluated