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


Copyright (c) 2001 - Apache Software Foundation