Package com.sun.xml.stream.buffer.stax

Class NamespaceContexHelper

java.lang.Object
com.sun.xml.stream.buffer.stax.NamespaceContexHelper
All Implemented Interfaces:
Iterable<NamespaceContextEx.Binding>, NamespaceContext, NamespaceContextEx
public final class NamespaceContexHelper extends Object implements NamespaceContextEx
A helper class for managing the declaration of namespaces.

A namespace is declared on a namespace context. Namespace contexts are pushed on and popped off the namespace context stack.

A declared namespace will be in scope iff the context that it was declared on has not been popped off the stack.

When instantiated the namespace stack consists of the root namespace context, which contains, by default, the "xml" and "xmlns" declarations. Namespaces may be declarations may be declared on the root context. The root context cannot be popped but can be reset to contain just the "xml" and "xmlns" declarations.

Implementation note: determining the prefix from a namespace URI (or vice versa) is efficient when there are few namespace declarations i.e. what is considered to be the case for namespace declarations in 'average' XML documents. The look up of a namespace URI given a prefix is performed in O(n) time. The look up of a prefix given a namespace URI is performed in O(2n) time.

The implementation does not scale when there are many namespace declarations. TODO: Use a hash map when there are many namespace declarations.

Author:
Paul.Sandoz@Sun.Com

  • Constructor Details

    • NamespaceContexHelper

      public NamespaceContexHelper()
      Create a new NamespaceContexHelper.

  • Method Details

    • getNamespaceURI

      public String getNamespaceURI(String prefix)
      Specified by:
      getNamespaceURI in interface NamespaceContext

    • getPrefix

      public String getPrefix(String namespaceURI)
      Specified by:
      getPrefix in interface NamespaceContext

    • getPrefixes

      public Iterator getPrefixes(String namespaceURI)
      Specified by:
      getPrefixes in interface NamespaceContext

    • iterator

      public Iterator<NamespaceContextEx.Binding> iterator()
      Description copied from interface: NamespaceContextEx
      Iterates all the in-scope namespace bindings.

      This method enumerates all the active in-scope namespace bindings. This does not include implicit bindings, such as "xml"->"http://www.w3.org/XML/1998/namespace" or ""->"" (the implicit default namespace URI.)

      The returned iterator may not include the same prefix more than once. For example, the returned iterator may only contain f=ns2 if the document is as follows and this method is used at the bar element. 

      
 <foo xmlns:f='ns1'>
   <bar xmlns:f='ns2'>
     ...

      The iteration may be done in no particular order.

      Specified by:
      iterator in interface Iterable<NamespaceContextEx.Binding>
      Specified by:
      iterator in interface NamespaceContextEx
      Returns:
      may return an empty iterator, but never null.

    • declareDefaultNamespace

      public void declareDefaultNamespace(String namespaceURI)
      Declare a default namespace.

      Parameters:
      namespaceURI - the namespace URI to declare, may be null.

    • declareNamespace

      public void declareNamespace(String prefix, String namespaceURI)
      Declare a namespace.

      The namespace will be declared on the current namespace context.

      The namespace can be removed by popping the current namespace context, or, if the declaration occured in the root context, by reseting the namespace context.

      A default namespace can be declared by passing "" as the value of the prefix parameter. A namespace may be undeclared by passing null as the value of the namespaceURI parameter.

      Parameters:
      prefix - the namespace prefix to declare, may not be null.
      namespaceURI - the namespace URI to declare, may be null.
      Throws:
      IllegalArgumentException - if the prefix is null.

    • pushContext

      public void pushContext()
      Push a namespace context on the stack.

    • popContext

      public void popContext()
      Pop the namespace context off the stack.

      Namespaces declared within the context (to be popped) will be removed and no longer be in scope.

    • resetContexts

      public void resetContexts()
      Reset namespace contexts.

      Pop all namespace contexts and reset the root context.