org.apache.commons.jxpath.ri.model.beans
Class NullElementPointer

java.lang.Object
  |
  +--org.apache.commons.jxpath.ri.model.NodePointer
        |
        +--org.apache.commons.jxpath.ri.model.beans.PropertyOwnerPointer
              |
              +--org.apache.commons.jxpath.ri.model.beans.NullElementPointer

All Implemented Interfaces:

java.lang.Cloneable, java.lang.Comparable, Pointer

public class NullElementPointer

extends PropertyOwnerPointer

Used when there is a need to construct a Pointer for a collection element that does not exist. For example, if the path is "foo[3]", but the collection "foo" only has one element or is empty or is null, the NullElementPointer can be used to capture this situatuin without putting a regular NodePointer into an invalid state. Just create a NullElementPointer with index 2 (= 3 - 1) and a "foo" pointer as the parent.

Version:

$Revision: 1.5 $ $Date: 2002/05/08 23:05:05 $

Author:

Dmitri Plotnikov

Field Summary

Fields inherited from class org.apache.commons.jxpath.ri.model.NodePointer

index, locale, parent, UNKNOWN_NAMESPACE, WHOLE_COLLECTION

Constructor Summary

NullElementPointer(NodePointer parent, int index)

Method Summary

java.lang.String	asPath() Returns an XPath that maps to this Pointer.
NodePointer	createChild(JXPathContext context, QName name, int index) Called by a child pointer when it needs to create a parent object for a non-existent collection element.
NodePointer	createChild(JXPathContext context, QName name, int index, java.lang.Object value) Called by a child pointer if that child needs to assign the value supplied in the createPath(context, value) call to a non-existent node.
NodePointer	createPath(JXPathContext context) Called by a child pointer when it needs to create a parent object.
NodePointer	createPath(JXPathContext context, java.lang.Object value) Called directly by JXPathContext.
boolean	equals(java.lang.Object object)
java.lang.Object	getBaseValue() Returns the value represented by the pointer before indexing.
int	getLength() If the pointer represents a collection (or collection element), returns the length of the collection.
QName	getName() Returns the name of this node.
java.lang.Object	getNodeValue() Returns the object the pointer points to; does not convert it to a "canonical" type.
PropertyPointer	getPropertyPointer()
NodePointer	getValuePointer() If this pointer manages a transparent container, like a variable, this method returns the pointer to the contents.
int	hashCode()
boolean	isActual() An actual pointer points to an existing part of an object graph, even if it is null.
boolean	isNode() If false, this node is axiliary and can only be used as an intermediate in the chain of pointers.
void	setValue(java.lang.Object value) Converts the value to the required type and changes the corresponding object to that value.

Methods inherited from class org.apache.commons.jxpath.ri.model.beans.PropertyOwnerPointer

attributeIterator, childIterator, compareChildNodePointers, isCollection, setIndex

Methods inherited from class org.apache.commons.jxpath.ri.model.NodePointer

clone, compareTo, getDefaultNamespaceURI, getExpandedName, getIndex, getLocale, getNamespaceURI, getNamespaceURI, getParent, getPointerByID, getPointerByKey, getValue, isDefaultNamespace, isLanguage, isLeaf, isRoot, namespaceIterator, namespacePointer, newChildNodePointer, newNodePointer, printPointerChain, remove, testNode, toString

Methods inherited from class java.lang.Object

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

Constructor Detail

NullElementPointer

public NullElementPointer(NodePointer parent,
                          int index)

Method Detail

getName

public QName getName()

Description copied from class: NodePointer

Returns the name of this node. Can be null.

Specified by:

getName in class PropertyOwnerPointer

getBaseValue

public java.lang.Object getBaseValue()

Description copied from class: NodePointer

Returns the value represented by the pointer before indexing. So, if the node represents an element of a collection, this method returns the collection itself.

Specified by:

getBaseValue in class NodePointer

getNodeValue

public java.lang.Object getNodeValue()

Description copied from class: NodePointer

Returns the object the pointer points to; does not convert it to a "canonical" type.

Overrides:

getNodeValue in class PropertyOwnerPointer

getPropertyPointer

public PropertyPointer getPropertyPointer()

Specified by:

getPropertyPointer in class PropertyOwnerPointer

getValuePointer

public NodePointer getValuePointer()

Description copied from class: NodePointer

If this pointer manages a transparent container, like a variable, this method returns the pointer to the contents. Only an auxiliary (non-node) pointer can (and should) return a value pointer other than itself.

Overrides:

getValuePointer in class NodePointer

setValue

public void setValue(java.lang.Object value)

Description copied from class: NodePointer

Converts the value to the required type and changes the corresponding object to that value.

Specified by:

setValue in interface Pointer

Overrides:

setValue in class PropertyOwnerPointer

isActual

public boolean isActual()

Description copied from class: NodePointer

An actual pointer points to an existing part of an object graph, even if it is null. A non-actual pointer represents a part that does not exist at all. For instance consider the pointer "/address/street". If both address and street are not null, the pointer is actual. If address is not null, but street is null, the pointer is still actual. If address is null, the pointer is not actual. (In JavaBeans) if address is not a property of the root bean, a Pointer for this path cannot be obtained at all - actual or otherwise.

Overrides:

isActual in class NodePointer

isNode

public boolean isNode()

Description copied from class: NodePointer

If false, this node is axiliary and can only be used as an intermediate in the chain of pointers.

Overrides:

isNode in class NodePointer

createPath

public NodePointer createPath(JXPathContext context,
                              java.lang.Object value)

Description copied from class: NodePointer

Called directly by JXPathContext. Must create path and set value.

Overrides:

createPath in class NodePointer

createPath

public NodePointer createPath(JXPathContext context)

Description copied from class: NodePointer

Called by a child pointer when it needs to create a parent object. Must create an object described by this pointer and return a new pointer that properly describes the new object.

Overrides:

createPath in class NodePointer

createChild

public NodePointer createChild(JXPathContext context,
                               QName name,
                               int index,
                               java.lang.Object value)

Description copied from class: NodePointer

Called by a child pointer if that child needs to assign the value supplied in the createPath(context, value) call to a non-existent node. This method must may have to expand the collection in order to assign the element.

Overrides:

createChild in class PropertyOwnerPointer

createChild

public NodePointer createChild(JXPathContext context,
                               QName name,
                               int index)

Description copied from class: NodePointer

Called by a child pointer when it needs to create a parent object for a non-existent collection element. It may have to expand the collection, then create an element object and return a new pointer describing the newly created element.

Overrides:

createChild in class PropertyOwnerPointer

hashCode

public int hashCode()

Overrides:

hashCode in class java.lang.Object

equals

public boolean equals(java.lang.Object object)

Overrides:

equals in class java.lang.Object

asPath

public java.lang.String asPath()

Description copied from class: NodePointer

Returns an XPath that maps to this Pointer.

Specified by:

asPath in interface Pointer

Overrides:

asPath in class NodePointer

getLength

public int getLength()

Description copied from class: NodePointer

If the pointer represents a collection (or collection element), returns the length of the collection. Otherwise returns 1 (even if the value is null).

Overrides:

getLength in class NodePointer