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

java.lang.Object
  extended byorg.apache.commons.jxpath.ri.model.NodePointer
      extended byorg.apache.commons.jxpath.ri.model.beans.CollectionPointer
          extended byorg.apache.commons.jxpath.ri.model.beans.NullElementPointer
All Implemented Interfaces:
java.lang.Cloneable, java.lang.Comparable, Pointer, java.io.Serializable

public class NullElementPointer
extends CollectionPointer

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 situation 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: 1.17 $ $Date: 2004/03/25 03:49:50 $
Author:
Dmitri Plotnikov
See Also:
Serialized Form

Field Summary
 
Fields inherited from class org.apache.commons.jxpath.ri.model.beans.CollectionPointer
 
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 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.
 java.lang.Object getImmediateNode()
          Returns the object the pointer points to; does not convert it to a "canonical" type.
 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.
 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 isCollection()
          Returns true if the value of the pointer is an array or a Collection.
 boolean isContainer()
          If true, this node is axiliary and can only be used as an intermediate in the chain of pointers.
 boolean isLeaf()
          If true, this node does not have children
 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.CollectionPointer
attributeIterator, childIterator, compareChildNodePointers, createChild, createChild, namespaceIterator, namespacePointer, setIndex, testNode
 
Methods inherited from class org.apache.commons.jxpath.ri.model.NodePointer
clone, compareTo, createAttribute, getDefaultNamespaceURI, getImmediateParentPointer, getImmediateValuePointer, getIndex, getLocale, getNamespaceResolver, getNamespaceURI, getNamespaceURI, getNode, getNodeValue, getParent, getPointerByID, getPointerByKey, getRootNode, getValue, isAttribute, isDefaultNamespace, isLanguage, isNode, isRoot, newChildNodePointer, newNodePointer, printPointerChain, remove, setAttribute, setNamespaceResolver, 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.

Overrides:
getName in class CollectionPointer

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.

Overrides:
getBaseValue in class CollectionPointer

getImmediateNode

public java.lang.Object getImmediateNode()
Description copied from class: NodePointer
Returns the object the pointer points to; does not convert it to a "canonical" type.

Overrides:
getImmediateNode in class CollectionPointer

isLeaf

public boolean isLeaf()
Description copied from class: NodePointer
If true, this node does not have children

Overrides:
isLeaf in class CollectionPointer

isCollection

public boolean isCollection()
Description copied from class: NodePointer
Returns true if the value of the pointer is an array or a Collection.

Overrides:
isCollection in class CollectionPointer

getPropertyPointer

public PropertyPointer getPropertyPointer()

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. Note that you probably don't want to override getValuePointer() directly. Override the getImmediateValuePointer() method instead. The getValuePointer() method is calls getImmediateValuePointer() and, if the result is not this, invokes getValuePointer() recursively. The idea here is to open all nested containers. Let's say we have a container within a container within a container. The getValuePointer() method should then open all those containers and return the pointer to the ultimate contents. It does so with the above recursion.

Overrides:
getValuePointer in class CollectionPointer

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 CollectionPointer

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

isContainer

public boolean isContainer()
Description copied from class: NodePointer
If true, this node is axiliary and can only be used as an intermediate in the chain of pointers.

Overrides:
isContainer in class CollectionPointer

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 CollectionPointer

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 CollectionPointer

hashCode

public int hashCode()
Overrides:
hashCode in class CollectionPointer

equals

public boolean equals(java.lang.Object object)
Overrides:
equals in class CollectionPointer

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 CollectionPointer

asPath

public java.lang.String asPath()
Description copied from class: CollectionPointer
Returns an XPath that maps to this Pointer.

Specified by:
asPath in interface Pointer
Overrides:
asPath in class CollectionPointer