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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, org.apache.commons.jxpath.Pointer, java.io.Serializable

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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 $

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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(org.apache.commons.jxpath.ri.model.NodePointer parent, int index)

 

Method Summary
java.lang.String	asPath()           Returns an XPath that maps to this Pointer.
org.apache.commons.jxpath.ri.model.NodePointer	createPath(org.apache.commons.jxpath.JXPathContext context)           Called by a child pointer when it needs to create a parent object.
org.apache.commons.jxpath.ri.model.NodePointer	createPath(org.apache.commons.jxpath.JXPathContext context, java.lang.Object value)           Called directly by JXPathContext.
boolean	equals(java.lang.Object object)           Determine whether this Object is semantically equal to another 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.
org.apache.commons.jxpath.ri.QName	getName()           Returns the name of this node.
PropertyPointer	getPropertyPointer()
org.apache.commons.jxpath.ri.model.NodePointer	getValuePointer()           If this pointer manages a transparent container, like a variable, this method returns the pointer to the contents.
int	hashCode()           Get a value that represents this Object, as uniquely as possible within the confines of an int.
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(org.apache.commons.jxpath.ri.model.NodePointer parent,
                          int index)

Method Detail

getName

public org.apache.commons.jxpath.ri.QName getName()

Description copied from class: org.apache.commons.jxpath.ri.model.NodePointer

Returns the name of this node. Can be null.

Overrides:

getName in class CollectionPointer

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getBaseValue

public java.lang.Object getBaseValue()

Description copied from class: org.apache.commons.jxpath.ri.model.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

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getImmediateNode

public java.lang.Object getImmediateNode()

Description copied from class: org.apache.commons.jxpath.ri.model.NodePointer

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

Overrides:

getImmediateNode in class CollectionPointer

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isLeaf

public boolean isLeaf()

Description copied from class: org.apache.commons.jxpath.ri.model.NodePointer

If true, this node does not have children

Overrides:

isLeaf in class CollectionPointer

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isCollection

public boolean isCollection()

Description copied from class: org.apache.commons.jxpath.ri.model.NodePointer

Returns true if the value of the pointer is an array or a Collection.

Overrides:

isCollection in class CollectionPointer

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getPropertyPointer

public PropertyPointer getPropertyPointer()

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getValuePointer

public org.apache.commons.jxpath.ri.model.NodePointer getValuePointer()

Description copied from class: org.apache.commons.jxpath.ri.model.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

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setValue

public void setValue(java.lang.Object value)

Description copied from class: org.apache.commons.jxpath.ri.model.NodePointer

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

Specified by:

setValue in interface org.apache.commons.jxpath.Pointer

Overrides:

setValue in class CollectionPointer

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isActual

public boolean isActual()

Description copied from class: org.apache.commons.jxpath.ri.model.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.

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isContainer

public boolean isContainer()

Description copied from class: org.apache.commons.jxpath.ri.model.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

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createPath

public org.apache.commons.jxpath.ri.model.NodePointer createPath(org.apache.commons.jxpath.JXPathContext context)

Description copied from class: org.apache.commons.jxpath.ri.model.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

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createPath

public org.apache.commons.jxpath.ri.model.NodePointer createPath(org.apache.commons.jxpath.JXPathContext context,
                                                                 java.lang.Object value)

Description copied from class: org.apache.commons.jxpath.ri.model.NodePointer

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

Overrides:

createPath in class CollectionPointer

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hashCode

public int hashCode()

Description copied from class: java.lang.Object

Get a value that represents this Object, as uniquely as possible within the confines of an int.

There are some requirements on this method which subclasses must follow:

• Semantic equality implies identical hashcodes. In other words, if a.equals(b) is true, then a.hashCode() == b.hashCode() must be as well. However, the reverse is not necessarily true, and two objects may have the same hashcode without being equal.
• It must be consistent. Whichever value o.hashCode() returns on the first invocation must be the value returned on all later invocations as long as the object exists. Notice, however, that the result of hashCode may change between separate executions of a Virtual Machine, because it is not invoked on the same object.

Notice that since hashCode is used in java.util.Hashtable and other hashing classes, a poor implementation will degrade the performance of hashing (so don't blindly implement it as returning a constant!). Also, if calculating the hash is time-consuming, a class may consider caching the results.

The default implementation returns System.identityHashCode(this)

Overrides:

hashCode in class CollectionPointer

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equals

public boolean equals(java.lang.Object object)

Description copied from class: java.lang.Object

Determine whether this Object is semantically equal to another Object.

There are some fairly strict requirements on this method which subclasses must follow:

• It must be transitive. If a.equals(b) and b.equals(c), then a.equals(c) must be true as well.
• It must be symmetric. a.equals(b) and b.equals(a) must have the same value.
• It must be reflexive. a.equals(a) must always be true.
• It must be consistent. Whichever value a.equals(b) returns on the first invocation must be the value returned on all later invocations.
• a.equals(null) must be false.
• It must be consistent with hashCode(). That is, a.equals(b) must imply a.hashCode() == b.hashCode(). The reverse is not true; two objects that are not equal may have the same hashcode, but that has the potential to harm hashing performance.

This is typically overridden to throw a java.lang.ClassCastException if the argument is not comparable to the class performing the comparison, but that is not a requirement. It is legal for a.equals(b) to be true even though a.getClass() != b.getClass(). Also, it is typical to never cause a java.lang.NullPointerException.

In general, the Collections API (java.util) use the equals method rather than the == operator to compare objects. However, java.util.IdentityHashMap is an exception to this rule, for its own good reasons.

The default implementation returns this == o.

Overrides:

equals in class CollectionPointer

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getLength

public int getLength()

Description copied from class: org.apache.commons.jxpath.ri.model.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

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asPath

public java.lang.String asPath()

Description copied from class: CollectionPointer

Returns an XPath that maps to this Pointer.

Specified by:

asPath in interface org.apache.commons.jxpath.Pointer

Overrides:

asPath in class CollectionPointer

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Overview  Package   Class  Use  Deprecated  Index
Home >> All >> org >> apache >> commons >> jxpath >> ri >> model >> [ beans overview ]	PREV CLASS  NEXT CLASS
SUMMARY:  JAVADOC |  SOURCE |  DOWNLOAD | NESTED | FIELD | CONSTR | METHOD	DETAIL: FIELD | CONSTR | METHOD

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