org.quattor.pan.dml.data

Class Null

java.lang.Object

org.quattor.pan.dml.data.Element

org.quattor.pan.dml.data.TransientElement

org.quattor.pan.dml.data.Null

All Implemented Interfaces:

Operation

@Immutable
public class Null
extends TransientElement

Represents a null value in the pan language.

Author:

loomis

Property Summary

Properties inherited from class org.quattor.pan.dml.data.Element

isProperty

Field Summary

Fields

Modifier and Type	Field and Description
static Null	VALUE

Method Summary

Methods

Modifier and Type	Method and Description
void	checkValidReplacement(Element newValue) Check that the newValue is a valid replacement for the this value.
boolean	equals(Object o) Require that all Elements implement an equals method.
static Null	getInstance()
String	getTypeAsString() All Elements must return a string describing its type.
int	hashCode() Require that all Elements implement the hashCode method.
String	locateUndefinedElement() Determine if the element contains any undefined (transient) elements.
Object	readResolve()
String	toString() Require that all Elements implement a reasonable toString method.

Methods inherited from class org.quattor.pan.dml.data.Element

checkInvalidSelfContext, checkRange, checkRestrictedContext, defined, duplicate, execute, exists, isBoolean, isDouble, isList, isLong, isNlist, isPersistent, isProperty, isProtected, isResource, isString, isTransient, protect, rget, rgetList, rput, writableCopy

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

VALUE

public static final Null VALUE

Method Detail

readResolve

public Object readResolve()
                   throws ObjectStreamException

Throws:

ObjectStreamException

getInstance

public static Null getInstance()

locateUndefinedElement

public String locateUndefinedElement()

Description copied from class: Element

Determine if the element contains any undefined (transient) elements. The call will return null if no undefined elements are found; it will return a string indicating the relative path if an undefined element is found. Subclasses MUST override this method appropriately. This default method will work only for elements which are not containers and not a transient element.

Overrides:

locateUndefinedElement in class Element

Returns:

String representation of the path of the undefined element, null otherwise

checkValidReplacement

public void checkValidReplacement(Element newValue)
                           throws EvaluationException

Description copied from class: Element

Check that the newValue is a valid replacement for the this value. This implementation will check if the newValue is assignable from the current value or that the newValue is either undef or null. If not, an evaluation exception will be thrown. This implementation should be overridden if more liberal replacements are allowed.

Overrides:

checkValidReplacement in class Element

Parameters:

newValue - the new value for the replacement

Throws:

EvaluationException - if the new value is not a valid replacement of the existing value

getTypeAsString

public String getTypeAsString()

Description copied from class: Element

All Elements must return a string describing its type. This value used in the serialization to machine profiles.

Specified by:

getTypeAsString in class Element

Returns:

String representation of Element's type

hashCode

public int hashCode()

Description copied from class: Element

Require that all Elements implement the hashCode method.

Specified by:

hashCode in class Element

equals

public boolean equals(Object o)

Description copied from class: Element

Require that all Elements implement an equals method.

Specified by:

equals in class Element

toString

public String toString()

Description copied from class: Element

Require that all Elements implement a reasonable toString method.

Specified by:

toString in class Element