Class NamespaceSupport

java.lang.Object
org.xml.sax.helpers.NamespaceSupport
public class NamespaceSupport extends Object
Encapsulate Namespace logic for use by applications using SAX, or internally by SAX drivers.

This class encapsulates the logic of Namespace processing: it tracks the declarations currently in force for each context and automatically processes qualified XML names into their Namespace parts; it can also be used in reverse for generating XML qnames from Namespaces.

Namespace support objects are reusable, but the reset method must be invoked between each session.

Here is a simple session:

String parts[] = new String[3];
NamespaceSupport support = new NamespaceSupport();

support.pushContext();
support.declarePrefix("", "http://www.w3.org/1999/xhtml");
support.declarePrefix("dc", "http://www.purl.org/dc#");

parts = support.processName("p", parts, false);
System.out.println("Namespace URI: " + parts[0]);
System.out.println("Local name: " + parts[1]);
System.out.println("Raw name: " + parts[2]);

parts = support.processName("dc:title", parts, false);
System.out.println("Namespace URI: " + parts[0]);
System.out.println("Local name: " + parts[1]);
System.out.println("Raw name: " + parts[2]);

support.popContext();

Note that this class is optimized for the use case where most elements do not contain Namespace declarations: if the same prefix/URI mapping is repeated for each context (for example), this class will be somewhat less efficient.

Although SAX drivers (parsers) may choose to use this class to implement namespace handling, they are not required to do so. Applications must track namespace information themselves if they want to use namespace information.

Since:
1.4, SAX 2.0

  • Field Details

    • XMLNS

      public static final String XMLNS
      The XML Namespace URI as a constant. The value is http://www.w3.org/XML/1998/namespace as defined in the "Namespaces in XML" * recommendation.

      This is the Namespace URI that is automatically mapped to the "xml" prefix.

      See Also:

    • NSDECL

      public static final String NSDECL
      The namespace declaration URI as a constant. The value is http://www.w3.org/xmlns/2000/, as defined in a backwards-incompatible erratum to the "Namespaces in XML" recommendation. Because that erratum postdated SAX2, SAX2 defaults to the original recommendation, and does not normally use this URI.

      This is the Namespace URI that is optionally applied to xmlns and xmlns:* attributes, which are used to declare namespaces.

      Since:
      1.5, SAX 2.1alpha
      See Also:

  • Constructor Details

    • NamespaceSupport

      public NamespaceSupport()
      Create a new Namespace support object.

  • Method Details

    • reset

      public void reset()
      Reset this Namespace support object for reuse.

      It is necessary to invoke this method before reusing the Namespace support object for a new session. If namespace declaration URIs are to be supported, that flag must also be set to a non-default value.

      See Also:

    • pushContext

      public void pushContext()
      Start a new Namespace context. The new context will automatically inherit the declarations of its parent context, but it will also keep track of which declarations were made within this context.

      Event callback code should start a new context once per element. This means being ready to call this in either of two places. For elements that don't include namespace declarations, the ContentHandler.startElement() callback is the right place. For elements with such a declaration, it'd done in the first ContentHandler.startPrefixMapping() callback. A boolean flag can be used to track whether a context has been started yet. When either of those methods is called, it checks the flag to see if a new context needs to be started. If so, it starts the context and sets the flag. After ContentHandler.startElement() does that, it always clears the flag.

      Normally, SAX drivers would push a new context at the beginning of each XML element. Then they perform a first pass over the attributes to process all namespace declarations, making ContentHandler.startPrefixMapping() callbacks. Then a second pass is made, to determine the namespace-qualified names for all attributes and for the element name. Finally all the information for the ContentHandler.startElement() callback is available, so it can then be made.

      The Namespace support object always starts with a base context already in force: in this context, only the "xml" prefix is declared.

      See Also:

    • popContext

      public void popContext()
      Revert to the previous Namespace context.

      Normally, you should pop the context at the end of each XML element. After popping the context, all Namespace prefix mappings that were previously in force are restored.

      You must not attempt to declare additional Namespace prefixes after popping a context, unless you push another context first.

      See Also:

    • declarePrefix

      public boolean declarePrefix(String prefix, String uri)
      Declare a Namespace prefix. All prefixes must be declared before they are referenced. For example, a SAX driver (parser) would scan an element's attributes in two passes: first for namespace declarations, then a second pass using processName() to interpret prefixes against (potentially redefined) prefixes.

      This method declares a prefix in the current Namespace context; the prefix will remain in force until this context is popped, unless it is shadowed in a descendant context.

      To declare the default element Namespace, use the empty string as the prefix.

      Note that there is an asymmetry in this library: getPrefix will not return the "" prefix, even if you have declared a default element namespace. To check for a default namespace, you have to look it up explicitly using getURI. This asymmetry exists to make it easier to look up prefixes for attribute names, where the default prefix is not allowed.

      Parameters:
      prefix - The prefix to declare, or the empty string to indicate the default element namespace. This may never have the value "xml" or "xmlns".
      uri - The Namespace URI to associate with the prefix.
      Returns:
      true if the prefix was legal, false otherwise
      See Also:

    • processName

      public String[] processName(String qName, String[