// NamespaceSupport.java - generic Namespace support for SAX.
// Written by David Megginson, sax@megginson.com
// This class is in the Public Domain. NO WARRANTY!
// $Id: NamespaceSupport.java,v 1.8 2000/05/05 17:49:53 david Exp $
package org.xml.sax.helpers;
import java.util.EmptyStackException;
import java.util.Enumeration;
import java.util.Hashtable;
import java.util.Vector;
/**
* Encapsulate Namespace logic for use by SAX drivers.
*
* <blockquote>
* <em>This module, both source code and documentation, is in the
* Public Domain, and comes with <strong>NO WARRANTY</strong>.</em>
* </blockquote>
*
* <p>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.</p>
*
* <p>Namespace support objects are reusable, but the reset method
* must be invoked between each session.</p>
*
* <p>Here is a simple session:</p>
*
* <pre>
* 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();
* </pre>
*
* <p>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.</p>
*
* @since SAX 2.0
* @author David Megginson,
* <a href="mailto:sax@megginson.com">sax@megginson.com</a>
* @version 2.0
*/
public class NamespaceSupport
{
////////////////////////////////////////////////////////////////////
// Constants.
////////////////////////////////////////////////////////////////////
/**
* The XML Namespace as a constant.
*
* <p>This is the Namespace URI that is automatically mapped
* to the "xml" prefix.</p>
*/
public final static String XMLNS =
"http://www.w3.org/XML/1998/namespace";
/**
* An empty enumeration.
*/
private final static Enumeration EMPTY_ENUMERATION =
new Vector().elements();
////////////////////////////////////////////////////////////////////
// Constructor.
////////////////////////////////////////////////////////////////////
/**
* Create a new Namespace support object.
*/
public NamespaceSupport ()
{
reset();
}
////////////////////////////////////////////////////////////////////
// Context management.
////////////////////////////////////////////////////////////////////
/**
* Reset this Namespace support object for reuse.
*
* <p>It is necessary to invoke this method before reusing the
* Namespace support object for a new session.</p>
*/
public void reset ()
{
contexts = new Context[32];
contextPos = 0;
contexts[contextPos] = currentContext = new Context();
currentContext.declarePrefix("xml", XMLNS);
}
/**
* Start a new Namespace context.
*
* <p>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.</p>
*
* <p>The Namespace support object always starts with a base context
* already in force: in this context, only the "xml" prefix is
* declared.</p>
*
* @see #popContext
*/
public void pushContext ()
{
int max = contexts.length;
contextPos++;
// Extend the array if necessary
if (contextPos >= max) {
Context newContexts[] = new Context[max*2];
System.arraycopy(contexts, 0, newContexts, 0, max);
max *= 2;
contexts = newContexts;
}
// Allocate the context if necessary.
currentContext = contexts[contextPos];
if (currentContext == null) {
contexts[contextPos] = currentContext = new Context();
}
// Set the parent, if any.
if (contextPos > 0) {
currentContext.setParent(contexts[contextPos - 1]);
}
}
/**
* Revert to the previous Namespace context.
*
* <p>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.</p>
*
* <p>You must not attempt to declare additional Namespace
* prefixes after popping a context, unless you push another
* context first.</p>
*
* @see #pushContext
*/
public void popContext ()
{
contextPos--;
if (contextPos < 0) {
throw new EmptyStackException();
}
currentContext = contexts[contextPos];
}
////////////////////////////////////////////////////////////////////
// Operations within a context.
////////////////////////////////////////////////////////////////////
/**
* Declare a Namespace prefix.
*
* <p>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.</p>
*
* <p>To declare a default Namespace, use the empty string. The
* prefix must not be "xml" or "xmlns".</p>
*
* <p>Note that you must <em>not</em> declare a prefix after
* you've pushed and popped another Namespace.</p>
*
* <p>Note that there is an asymmetry in this library: while {@link
* #getPrefix getPrefix} will not return the default "" prefix,
* even if you have declared one; to check for a default prefix,
* you have to look it up explicitly using {@link #getURI getURI}.
* This asymmetry exists to make it easier to look up prefixes
* for attribute names, where the default prefix is not allowed.</p>
*
* @param prefix The prefix to declare, or null for the empty
* string.
* @param uri The Namespace URI to associate with the prefix.
* @return true if the prefix was legal, false otherwise
* @see #processName
* @see #getURI
* @see #getPrefix
*/
public boolean declarePrefix (String prefix, String uri)
{
if (prefix.equals("xml") || prefix.equals("xmlns")) {
return false;
} else {
currentContext.declarePrefix(prefix, uri);
return true;
}
}
/**
* Process a raw XML 1.0 name.
*
* <p>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:</p>
*
* <dl>
* <dt>parts[0]</dt>
* <dd>The Namespace URI, or an empty string if none is
* in use.</dd>
* <dt>parts[1]</dt>
* <dd>The local name (without prefix).</dd>
* <dt>parts[2]</dt>
* <dd>The original raw name.</dd>
* </dl>
*
* <p>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.</p>
*
* <p>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.</p>
*
* @param qName The raw XML 1.0 name to be processed.
* @param parts An array supplied by the caller, capable of
* holding at least three members.
* @param isAttribute A flag indicating whether this is an
* attribute name (true) or an element name (false).
* @return 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 #declarePrefix
* @see String#intern */
public String [] processName (String qName, String parts[],
boolean isAttribute)
{
String myParts[] = currentContext.processName(qName, isAttribute);
if (myParts == null) {
return null;
} else {
parts[0] = myParts[0];
parts[1] = myParts[1];
parts[2] = myParts[2];
return parts;
}
}
/**
* Look up a prefix and get the currently-mapped Namespace URI.
*
* <p>This method looks up the prefix in the current context.
* Use the empty string ("") for the default Namespace.</p>
*
* @param prefix The prefix to look up.
* @return The associated Namespace URI, or null if the prefix
* is undeclared in this context.
* @see #getPrefix
* @see #getPrefixes
*/
public String getURI (String prefix)
{
return currentContext.getURI(prefix);
}
/**
* Return an enumeration of all prefixes currently declared.
*
* <p><strong>Note:</strong> if there is a default prefix, it will not be
* returned in this enumeration; check for the default prefix
* using the {@link #getURI getURI} with an argument of "".</p>
*
* @return An enumeration of all prefixes declared in the
* current context except for the empty (default)
* prefix.
* @see #getDeclaredPrefixes
* @see #getURI
*/
public Enumeration getPrefixes ()
{
return currentContext.getPrefixes();
}
/**
* Return one of the prefixes mapped to a Namespace URI.
*
* <p>If more than one prefix is currently mapped to the same
* URI, this method will make an arbitrary selection; if you
* want all of the prefixes, use the {@link #getPrefixes}
* method instead.</p>
*
* <p><strong>Note:</strong> this will never return the empty (default) prefix;
* to check for a default prefix, use the {@link #getURI getURI}
* method with an argument of "".</p>
*
* @param uri The Namespace URI.
* @param isAttribute true if this prefix is for an attribute
* (and the default Namespace is not allowed).
* @return 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 #getPrefixes(String)
* @see #getURI
*/
public String getPrefix (String uri)
{
return currentContext.getPrefix(uri);
}
/**
* Return an enumeration of all prefixes currently declared for a URI.
*
* <p>This method returns prefixes mapped to a specific Namespace
* URI. The xml: prefix will be included. If you want only one
* prefix that's mapped to the Namespace URI, and you don't care
* which one you get, use the {@link #getPrefix getPrefix}
* method instead.</p>
*
* <p><strong>Note:</strong> the empty (default) prefix is <em>never</em> included
* in this enumeration; to check for the presence of a default
* Namespace, use the {@link #getURI getURI} method with an
* argument of "".</p>
*
* @param uri The Namespace URI.
* @return An enumeration of all prefixes declared in the
* current context.
* @see #getPrefix
* @see #getDeclaredPrefixes
* @see #getURI
*/
public Enumeration getPrefixes (String uri)
{
Vector prefixes = new Vector();
Enumeration allPrefixes = getPrefixes();
while (allPrefixes.hasMoreElements()) {
String prefix = (String)allPrefixes.nextElement();
if (uri.equals(getURI(prefix))) {
prefixes.addElement(prefix);
}
}
return prefixes.elements();
}
/**
* Return an enumeration of all prefixes declared in this context.
*
* <p>The empty (default) prefix will be included in this
* enumeration; note that this behaviour differs from that of
* {@link #getPrefix} and {@link #getPrefixes}.</p>
*
* @return An enumeration of all prefixes declared in this
* context.
* @see #getPrefixes
* @see #getURI
*/
public Enumeration getDeclaredPrefixes ()
{
return currentContext.getDeclaredPrefixes();
}
////////////////////////////////////////////////////////////////////
// Internal state.
////////////////////////////////////////////////////////////////////
private Context contexts[];
private Context currentContext;
private int contextPos;
////////////////////////////////////////////////////////////////////
// Internal classes.
////////////////////////////////////////////////////////////////////
/**
* Internal class for a single Namespace context.
*
* <p>This module caches and reuses Namespace contexts, so the number allocated
* will be equal to the element depth of the document, not to the total
* number of elements (i.e. 5-10 rather than tens of thousands).</p>
*/
final class Context {
/**
* Create the root-level Namespace context.
*/
Context ()
{
copyTables();
}
/**
* (Re)set the parent of this Namespace context.
*
* @param context The parent Namespace context object.
*/
void setParent (Context parent)
{
this.parent = parent;
declarations = null;
prefixTable = parent.prefixTable;
uriTable = parent.uriTable;
elementNameTable = parent.elementNameTable;
attributeNameTable = parent.attributeNameTable;
defaultNS = parent.defaultNS;
tablesDirty = false;
}
/**
* Declare a Namespace prefix for this context.
*
* @param prefix The prefix to declare.
* @param uri The associated Namespace URI.
* @see NamespaceSupport#declarePrefix
*/
void declarePrefix (String prefix, String uri)
{
// Lazy processing...
if (!tablesDirty) {
copyTables();
}
if (declarations == null) {
declarations = new Vector();
}
prefix = prefix.intern();
uri = uri.intern();
if ("".equals(prefix)) {
if ("".equals(uri)) {
defaultNS = null;
} else {
defaultNS = uri;
}
} else {
prefixTable.put(prefix, uri);
uriTable.put(uri, prefix); // may wipe out another prefix
}
declarations.addElement(prefix);
}
/**
* Process a raw XML 1.0 name in this context.
*
* @param qName The raw XML 1.0 name.
* @param isAttribute true if this is an attribute name.
* @return An array of three strings containing the
* URI part (or empty string), the local part,
* and the raw name, all internalized, or null
* if there is an undeclared prefix.
* @see NamespaceSupport#processName
*/
String [] processName (String qName, boolean isAttribute)
{
String name[];
Hashtable table;
// Select the appropriate table.
if (isAttribute) {
table = elementNameTable;
} else {
table = attributeNameTable;
}
// Start by looking in the cache, and
// return immediately if the name
// is already known in this content
name = (String[])table.get(qName);
if (name != null) {
return name;
}
// We haven't seen this name in this
// context before.
name = new String[3];
int index = qName.indexOf(':');
// No prefix.
if (index == -1) {
if (isAttribute || defaultNS == null) {
name[0] = "";
} else {
name[0] = defaultNS;
}
name[1] = qName.intern();
name[2] = name[1];
}
// Prefix
else {
String prefix = qName.substring(0, index);
String local = qName.substring(index+1);
String uri;
if ("".equals(prefix)) {
uri = defaultNS;
} else {
uri = (String)prefixTable.get(prefix);
}
if (uri == null) {
return null;
}
name[0] = uri;
name[1] = local.intern();
name[2] = qName.intern();
}
// Save in the cache for future use.
table.put(name[2], name);
tablesDirty = true;
return name;
}
/**
* Look up the URI associated with a prefix in this context.
*
* @param prefix The prefix to look up.
* @return The associated Namespace URI, or null if none is
* declared.
* @see NamespaceSupport#getURI
*/
String getURI (String prefix)
{
if ("".equals(prefix)) {
return defaultNS;
} else if (prefixTable == null) {
return null;
} else {
return (String)prefixTable.get(prefix);
}
}
/**
* Look up one of the prefixes associated with a URI in this context.
*
* <p>Since many prefixes may be mapped to the same URI,
* the return value may be unreliable.</p>
*
* @param uri The URI to look up.
* @return The associated prefix, or null if none is declared.
* @see NamespaceSupport#getPrefix
*/
String getPrefix (String uri)
{
if (uriTable == null) {
return null;
} else {
return (String)uriTable.get(uri);
}
}
/**
* Return an enumeration of prefixes declared in this context.
*
* @return An enumeration of prefixes (possibly empty).
* @see NamespaceSupport#getDeclaredPrefixes
*/
Enumeration getDeclaredPrefixes ()
{
if (declarations == null) {
return EMPTY_ENUMERATION;
} else {
return declarations.elements();
}
}
/**
* Return an enumeration of all prefixes currently in force.
*
* <p>The default prefix, if in force, is <em>not</em>
* returned, and will have to be checked for separately.</p>
*
* @return An enumeration of prefixes (never empty).
* @see NamespaceSupport#getPrefixes
*/
Enumeration getPrefixes ()
{
if (prefixTable == null) {
return EMPTY_ENUMERATION;
} else {
return prefixTable.keys();
}
}
////////////////////////////////////////////////////////////////
// Internal methods.
////////////////////////////////////////////////////////////////
/**
* Copy on write for the internal tables in this context.
*
* <p>This class is optimized for the normal case where most
* elements do not contain Namespace declarations.</p>
*/
private void copyTables ()
{
if (prefixTable != null) {
prefixTable = (Hashtable)prefixTable.clone();
} else {
prefixTable = new Hashtable();
}
if (uriTable != null) {
uriTable = (Hashtable)uriTable.clone();
} else {
uriTable = new Hashtable();
}
elementNameTable = new Hashtable();
attributeNameTable = new Hashtable();
tablesDirty = true;
}
////////////////////////////////////////////////////////////////
// Protected state.
////////////////////////////////////////////////////////////////
Hashtable prefixTable;
Hashtable uriTable;
Hashtable elementNameTable;
Hashtable attributeNameTable;
String defaultNS = null;
////////////////////////////////////////////////////////////////
// Internal state.
////////////////////////////////////////////////////////////////
private Vector declarations = null;
private boolean tablesDirty = false;
private Context parent = null;
}
}
// end of NamespaceSupport.java