Module java.xml
Package javax.xml.namespace

# Interface NamespaceContext

public interface NamespaceContext
Interface for read only XML Namespace context processing.

An XML Namespace has the properties:

- Namespace URI: Namespace name expressed as a URI to which the prefix is bound
- prefix: syntactically, this is the part of the attribute name following the `XMLConstants.XMLNS_ATTRIBUTE` ("xmlns") in the Namespace declaration

example: `<element xmlns:prefix="http://Namespace-name-URI">`

All `get*(*)` methods operate in the current scope for Namespace URI and prefix resolution.

Note that a Namespace URI can be bound to multiple prefixes in the current scope. This can occur when multiple `XMLConstants.XMLNS_ATTRIBUTE` ("xmlns") Namespace declarations occur in the same Start-Tag and refer to the same Namespace URI. e.g.

     <element xmlns:prefix1="http://Namespace-name-URI"
              xmlns:prefix2="http://Namespace-name-URI">

This can also occur when the same Namespace URI is used in multiple `XMLConstants.XMLNS_ATTRIBUTE` ("xmlns") Namespace declarations in the logical parent element hierarchy. e.g.

     <parent xmlns:prefix1="http://Namespace-name-URI">
       <child xmlns:prefix2="http://Namespace-name-URI">
         ...
       </child>
     </parent>

A prefix can only be bound to a single Namespace URI in the current scope.

Since:
  1.5
See Also:
  - `javax.xml.XMLConstants for declarations of common XML values`
  - XML Schema Part2: Datatypes
  - Namespaces in XML

## Method Summary

Modifier and Type
Method
Description
`String`
`getNamespaceURI(String prefix)`
Get Namespace URI bound to a prefix in the current scope.
`String`
`getPrefix(String namespaceURI)`
Get prefix bound to Namespace URI in the current scope.
`Iterator<String>`
`getPrefixes(String namespaceURI)`
Get all prefixes bound to a Namespace URI in the current scope.

## Method Details

### getNamespaceURI

String getNamespaceURI(String prefix)
Get Namespace URI bound to a prefix in the current scope.

When requesting a Namespace URI by prefix, the following table describes the returned Namespace URI value for all possible prefix values:

Return value for specified prefixes
prefix parameter | Namespace URI return value
--- | ---
`DEFAULT_NS_PREFIX` ("") | default Namespace URI in the current scope or ``XMLConstants.NULL_NS_URI("")`` when there is no default Namespace URI in the current scope
bound prefix | Namespace URI bound to prefix in current scope
unbound prefix | ``XMLConstants.NULL_NS_URI("")``
`XMLConstants.XML_NS_PREFIX` ("xml") | `XMLConstants.XML_NS_URI` ("http://www.w3.org/XML/1998/namespace")
`XMLConstants.XMLNS_ATTRIBUTE` ("xmlns") | `XMLConstants.XMLNS_ATTRIBUTE_NS_URI` ("http://www.w3.org/2000/xmlns/")
`null` | `IllegalArgumentException` is thrown

Parameters:
  `prefix` - prefix to look up
Returns:
  Namespace URI bound to prefix in the current scope
Throws:
  `IllegalArgumentException` - When `prefix` is `null`

### getPrefix

String getPrefix(String namespaceURI)
Get prefix bound to Namespace URI in the current scope.

To get all prefixes bound to a Namespace URI in the current scope, use `getPrefixes(String namespaceURI)`.

When requesting a prefix by Namespace URI, the following table describes the returned prefix value for all Namespace URI values:

Return value for specified Namespace URIs
Namespace URI parameter | prefix value returned
--- | ---
`<default Namespace URI>` | `XMLConstants.DEFAULT_NS_PREFIX` ("")
bound Namespace URI | prefix bound to Namespace URI in the current scope, if multiple prefixes are bound to the Namespace URI in the current scope, a single arbitrary prefix, whose choice is implementation dependent, is returned
unbound Namespace URI | `null`
`XMLConstants.XML_NS_URI` ("http://www.w3.org/XML/1998/namespace") | `XMLConstants.XML_NS_PREFIX` ("xml")
`XMLConstants.XMLNS_ATTRIBUTE_NS_URI` ("http://www.w3.org/2000/xmlns/") | `XMLConstants.XMLNS_ATTRIBUTE` ("xmlns")
`null` | `IllegalArgumentException` is thrown

Parameters:
  `namespaceURI` - URI of Namespace to lookup
Returns:
  prefix bound to Namespace URI in current context
Throws:
  `IllegalArgumentException` - When `namespaceURI` is `null`

### getPrefixes

Iterator<String> getPrefixes(String namespaceURI)
Get all prefixes bound to a Namespace URI in the current scope.

An Iterator over String elements is returned in an arbitrary, implementation dependent, order.

The `Iterator` is not modifiable. e.g. the `remove()` method will throw `UnsupportedOperationException`.

When requesting prefixes by Namespace URI, the following table describes the returned prefixes value for all Namespace URI values:

Return value for specified Namespace URIs
Namespace URI parameter | prefixes value returned
--- | ---
bound Namespace URI, including the `<default Namespace URI>` | `Iterator` over prefixes bound to Namespace URI in the current scope in an arbitrary, implementation dependent, order
unbound Namespace URI | empty `Iterator`
`XMLConstants.XML_NS_URI` ("http://www.w3.org/XML/1998/namespace") | `Iterator` with one element set to `XMLConstants.XML_NS_PREFIX` ("xml")
`XMLConstants.XMLNS_ATTRIBUTE_NS_URI` ("http://www.w3.org/2000/xmlns/") | `Iterator` with one element set to `XMLConstants.XMLNS_ATTRIBUTE` ("xmlns")
`null` | `IllegalArgumentException` is thrown

Parameters:
  `namespaceURI` - URI of Namespace to lookup
Returns:
  `Iterator` for all prefixes bound to the Namespace URI in the current scope
Throws:
  `IllegalArgumentException` - When `namespaceURI` is `null`