org.xml.sax.helpers

Class NamespaceSupport


public class NamespaceSupport
extends java.lang.Object

Encapsulate Namespace logic for use by SAX drivers.
This module, both source code and documentation, is in the Public Domain, and comes with NO WARRANTY.

This class encapsulates the logic of Namespace processing: it tracks the declarations currently in force for each context and automatically processes qualified XML 1.0 names into their Namespace parts; it can also be used in reverse for generating XML 1.0 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#");

 String 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]);
 String 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.

Version:
2.0r2pre
Author:
David Megginson, sax@megginson.com
Since:
SAX 2.0

Field Summary

static String
XMLNS
The XML Namespace as a constant.

Constructor Summary

NamespaceSupport()
Create a new Namespace support object.

Method Summary

boolean
declarePrefix(String prefix, String uri)
Declare a Namespace prefix.
Enumeration
getDeclaredPrefixes()
Return an enumeration of all prefixes declared in this context.
String
getPrefix(String uri)
Return one of the prefixes mapped to a Namespace URI.
Enumeration
getPrefixes()
Return an enumeration of all prefixes currently declared.
Enumeration
getPrefixes(String uri)
Return an enumeration of all prefixes currently declared for a URI.
String
getURI(String prefix)
Look up a prefix and get the currently-mapped Namespace URI.
void
popContext()
Revert to the previous Namespace context.
String[]
processName(String qName, parts[] , boolean isAttribute)
Process a raw XML 1.0 name.
void
pushContext()
Start a new Namespace context.
void
reset()
Reset this Namespace support object for reuse.

Field Details

XMLNS

public static final String XMLNS
The XML Namespace as a constant.

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

Constructor Details

NamespaceSupport

public NamespaceSupport()
Create a new Namespace support object.

Method Details

declarePrefix

public boolean declarePrefix(String prefix,
                             String uri)
Parameters:
prefix - The prefix to declare, or null for the empty string.
uri - The Namespace URI to associate with the prefix.
Returns:
true if the prefix was legal, false otherwise

getDeclaredPrefixes

public Enumeration getDeclaredPrefixes()
Returns:
An enumeration of all prefixes declared in this context.
See Also:
getPrefixes, getURI(String)

getPrefix

public String getPrefix(String uri)
Parameters:
uri - The Namespace URI.
Returns:
One of the prefixes currently mapped to the URI supplied, or null if none is mapped or if the URI is assigned to the default Namespace.
See Also:
getPrefixes(java.lang.String), getURI(String)

getPrefixes

public Enumeration getPrefixes()
Returns:
An enumeration of all prefixes declared in the current context except for the empty (default) prefix.

getPrefixes

public Enumeration getPrefixes(String uri)
Parameters:
uri - The Namespace URI.
Returns:
An enumeration of all prefixes declared in the current context.

getURI

public String getURI(String prefix)
Look up a prefix and get the currently-mapped Namespace URI.

This method looks up the prefix in the current context. Use the empty string ("") for the default Namespace.

Parameters:
prefix - The prefix to look up.
Returns:
The associated Namespace URI, or null if the prefix is undeclared in this context.

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.


processName

public String[] processName(String qName,
                            parts[] ,
                            boolean isAttribute)
Process a raw XML 1.0 name.

This method processes a raw XML 1.0 name in the current context by removing the prefix and looking it up among the prefixes currently declared. The return value will be the array supplied by the caller, filled in as follows:

All of the strings in the array will be internalized. If the raw name has a prefix that has not been declared, then the return value will be null.

Note that attribute names are processed differently than element names: an unprefixed element name will received the default Namespace (if any), while an unprefixed element name will not.

Parameters:
qName - The raw XML 1.0 name to be processed.
isAttribute - A flag indicating whether this is an attribute name (true) or an element name (false).
Returns:
The supplied array holding three internalized strings representing the Namespace URI (or empty string), the local name, and the raw XML 1.0 name; or null if there is an undeclared prefix.
See Also:
declarePrefix(String,String), java.lang.String.intern

pushContext

public void pushContext()
Start a new Namespace context.

Normally, you should push a new context at the beginning of each XML element: 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.

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


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.