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.CollectionPointer
          org.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