Class QName

java.lang.Object

javax.xml.namespace.QName

All Implemented Interfaces:

Serializable

public class QName
extends Object
implements Serializable

QName represents a qualified name as defined in the XML specifications: XML Schema Part2: Datatypes specification, Namespaces in XML.

The value of a QName contains a Namespace URI, local part and prefix.

The prefix is included in QName to retain lexical information when present in an XML input source. The prefix is NOT used in QName.equals(Object) or to compute the QName.hashCode(). Equality and the hash code are defined using only the Namespace URI and local part.

If not specified, the Namespace URI is set to XMLConstants.NULL_NS_URI. If not specified, the prefix is set to XMLConstants.DEFAULT_NS_PREFIX.

QName is immutable.

Since:

1.5

See Also:

• XML Schema Part2: Datatypes specification
• Namespaces in XML
• Serialized Form

Constructor Summary

Constructors

Constructor	Description
QName(String localPart)	QName constructor specifying the local part.
QName(String namespaceURI, String localPart)	QName constructor specifying the Namespace URI and local part.
QName(String namespaceURI, String localPart, String prefix)	QName constructor specifying the Namespace URI, local part and prefix.

Method Summary

Modifier and Type	Method	Description
final boolean	equals(Object objectToTest)	Test this QName for equality with another Object.
String	getLocalPart()	Get the local part of this QName.
String	getNamespaceURI()	Get the Namespace URI of this QName.
String	getPrefix()	Get the prefix of this QName.
final int	hashCode()	Generate the hash code for this QName.
String	toString()	Returns the string representation of this QName.
static QName	valueOf(String qNameAsString)	Returns a QName from its string representation.

Methods declared in class Object

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

Constructor Details

QName

public QName(String namespaceURI,
 String localPart)

QName constructor specifying the Namespace URI and local part.

If the Namespace URI is null, it is set to XMLConstants.NULL_NS_URI. This value represents no explicitly defined Namespace as defined by the Namespaces in XML specification. This action preserves compatible behavior with QName 1.0. Explicitly providing the XMLConstants.NULL_NS_URI value is the preferred coding style.

If the local part is null an IllegalArgumentException is thrown. A local part of "" is allowed to preserve compatible behavior with QName 1.0.

When using this constructor, the prefix is set to XMLConstants.DEFAULT_NS_PREFIX.

The Namespace URI is not validated as a URI reference. The local part is not validated as a NCName as specified in Namespaces in XML.

Parameters:

namespaceURI - Namespace URI of the QName

localPart - local part of the QName

Throws:

IllegalArgumentException - When localPart is null

See Also:

• QName(String namespaceURI, String localPart, String prefix)

QName

public QName(String namespaceURI,
 String localPart,
 String prefix)

QName constructor specifying the Namespace URI, local part and prefix.

If the Namespace URI is null, it is set to XMLConstants.NULL_NS_URI. This value represents no explicitly defined Namespace as defined by the Namespaces in XML specification. This action preserves compatible behavior with QName 1.0. Explicitly providing the XMLConstants.NULL_NS_URI value is the preferred coding style.

If the local part is null an IllegalArgumentException is thrown. A local part of "" is allowed to preserve compatible behavior with QName 1.0.

If the prefix is null, an IllegalArgumentException is thrown. Use XMLConstants.DEFAULT_NS_PREFIX to explicitly indicate that no prefix is present or the prefix is not relevant.

The Namespace URI is not validated as a URI reference. The local part and prefix are not validated as a NCName as specified in Namespaces in XML.

Parameters:

namespaceURI - Namespace URI of the QName

localPart - local part of the QName

prefix - prefix of the QName

Throws:

IllegalArgumentException - When localPart or prefix is null

QName

public QName(String localPart)

QName constructor specifying the local part.

If the local part is null an IllegalArgumentException is thrown. A local part of "" is allowed to preserve compatible behavior with QName 1.0.

When using this constructor, the Namespace URI is set to XMLConstants.NULL_NS_URI and the prefix is set to XMLConstants.DEFAULT_NS_PREFIX.

In an XML context, all Element and Attribute names exist in the context of a Namespace. Making this explicit during the construction of a QName helps prevent hard to diagnosis XML validity errors. The constructors QName(String namespaceURI, String localPart) and QName(String namespaceURI, String localPart, String prefix) are preferred.

The local part is not validated as a NCName as specified in Namespaces in XML.

Parameters:

localPart - local part of the QName

Throws:

IllegalArgumentException - When localPart is null

See Also:

• QName(String namespaceURI, String localPart)
• QName(String namespaceURI, String localPart, String prefix)

Method Details

getNamespaceURI

public String getNamespaceURI()

Get the Namespace URI of this QName.

Returns:

Namespace URI of this QName

getLocalPart

public String getLocalPart()

Get the local part of this QName.

Returns:

local part of this QName

getPrefix

public String getPrefix()

Get the prefix of this QName.

The prefix assigned to a QName might NOT be valid in a different context. For example, a QName may be assigned a prefix in the context of parsing a document but that prefix may be invalid in the context of a different document.

Returns:

prefix of this QName

equals

public final boolean equals(Object objectToTest)

Test this QName for equality with another Object.

If the Object to be tested is not a QName or is null, then this method returns false.

Two QNames are considered equal if and only if both the Namespace URI and local part are equal. This method uses String.equals() to check equality of the Namespace URI and local part. The prefix is NOT used to determine equality.

This method satisfies the general contract of Object.equals(Object)

Overrides:

equals in class Object

Parameters:

objectToTest - the Object to test for equality with this QName

Returns:

true if the given Object is equal to this QName else false

See Also:

• Object.hashCode()
• HashMap

hashCode

public final int hashCode()

Generate the hash code for this QName.

The hash code is calculated using both the Namespace URI and the local part of the QName. The prefix is NOT used to calculate the hash code.

This method satisfies the general contract of Object.hashCode().

Overrides:

hashCode in class Object

Returns:

hash code for this QName Object

See Also:

• Object.equals(java.lang.Object)
• System.identityHashCode(Object)

toString

public String toString()

Returns the string representation of this QName. The format is:

 
     {NamespaceURI}LocalPart
 

If NamespaceURI is null, only LocalPart is returned.

Overrides:

toString in class Object

API Note:

The Prefix is not returned in the string representation.

Returns:

the string representation of this QName

valueOf

public static QName valueOf(String qNameAsString)

Returns a QName from its string representation. The string representation must be in the format returned by toString():

 
     {NamespaceURI}LocalPart
 

Since the Prefix is not represented in the string form, it will be set to XMLConstants.DEFAULT_NS_PREFIX.

API Note:

This method does not perform full validation of the resulting QName. The NamespaceURI is not validated as a URI reference. The LocalPart is not validated as a NCName as specified in Namespaces in XML.

Parameters:

qNameAsString - the string representation of the QName

Returns:

a QName from its string representation

Throws:

IllegalArgumentException - if qNameAsString is null or malformed

See Also:

• QName.toString()