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Posted to commits@xalan.apache.org by jk...@apache.org on 2001/08/03 19:05:23 UTC
cvs commit: xml-xalan/java/src/org/apache/xml/utils NamespaceSupport2.java
jkesselm 01/08/03 10:05:23
Added: java/src/org/apache/xml/utils NamespaceSupport2.java
Log:
Replacement for org.xml.sax.helpers.NamespaceSupport; extends
that API so it can be easily swapped in.
Current changes;
Minor code reorg. I'm sorry, but I find classes easier to read
if fields are defined before methods reference them rather than
at end, especially when inner classes are present.
Punt stack vector in favor of doubly-linked list. (It was already
singly-linked in parallel with the vector!)
The whole dirty-tables concept was broken, because Context's
ctor always called copyTables and thus always marked tables
dirty. It also wasted some time setting itself only to be reset by
setParent. I've fixed both by parameterizing the ctor and making
copyTables specific to prep-for-new-declaration. (Could be
moved back into the declaration method, for that matter.)
I'm dubious about the caches in processName. As far as I can
tell, Xalan per se never actually uses that method...
The use of Hashtables is questionable. Hashtable is
known to be inefficient and oversynchronized in older JVMs, and
the fact that this is a bidirectional mapping suggests that an
approach similar to our own String Pool -- lighter-weight, more
targeted, hashing without reduplicating the two column tables --
would be a win. Since these are typically short sets, even
simple linear search is worth considering!
Revision Changes Path
1.1 xml-xalan/java/src/org/apache/xml/utils/NamespaceSupport2.java
Index: NamespaceSupport2.java
===================================================================
/*
* The Apache Software License, Version 1.1
*
*
* Copyright (c) 1999 The Apache Software Foundation. All rights
* reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* 3. The end-user documentation included with the redistribution,
* if any, must include the following acknowledgment:
* "This product includes software developed by the
* Apache Software Foundation (http://www.apache.org/)."
* Alternately, this acknowledgment may appear in the software itself,
* if and wherever such third-party acknowledgments normally appear.
*
* 4. The names "Xalan" and "Apache Software Foundation" must
* not be used to endorse or promote products derived from this
* software without prior written permission. For written
* permission, please contact apache@apache.org.
*
* 5. Products derived from this software may not be called "Apache",
* nor may "Apache" appear in their name, without prior written
* permission of the Apache Software Foundation.
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
* ====================================================================
*
* This software consists of voluntary contributions made by many
* individuals on behalf of the Apache Software Foundation and was
* originally based on software copyright (c) 1999, Lotus
* Development Corporation., http://www.lotus.com. For more
* information on the Apache Software Foundation, please see
* <http://www.apache.org/>.
*/
package org.apache.xml.utils;
import java.util.EmptyStackException;
import java.util.Enumeration;
import java.util.Hashtable;
import java.util.Vector;
/**
* Encapsulate Namespace tracking logic for use by SAX drivers.
*
* <p>This class is an attempt to rewrite the SAX NamespaceSupport
* "helper" class for improved efficiency. It can be used to track the
* namespace declarations currently in scope, providing lookup
* routines to map prefixes to URIs and vice versa.</p>
*
* <p>ISSUE: For testing purposes, I've extended NamespaceSupport even
* though I'm completely reasserting all behaviors and fields.
* Wasteful.... But SAX did not put an interface under that object and
* we seem to have written that SAX class into our APIs... and I don't
* want to argue with it right now. </p>
*
* @see org.xml.sax.helpers.NamespaceSupport
* */
public class NamespaceSupport2
extends org.xml.sax.helpers.NamespaceSupport
{
////////////////////////////////////////////////////////////////////
// Internal state.
////////////////////////////////////////////////////////////////////
private Context currentContext; // Current point on a linked list
////////////////////////////////////////////////////////////////////
// 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 NamespaceSupport2 ()
{
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 ()
{
// JJK: Discarding the whole stack doesn't save us a lot versus
// creating a new NamespaceSupport. Do we care, or should we
// change this to just reset the root context?
currentContext = new Context(null);
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 ()
{
// JJK: Context has a parent pointer.
// That means we don't need a stack to pop.
// We may want to retain for reuse, but that can be done via
// a child pointer.
Context parentContext=currentContext;
currentContext = parentContext.getChild();
if (currentContext == null){
currentContext = new Context(parent);
}
else{
// JJK: This will wipe out any leftover data
// if we're reusing a previously allocated Context.
currentContext.setParent(parentContext);
}
}
/**
* 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 ()
{
Context parentContext=currentContext.getParent();
if(parentContext==null)
throw new EmptyStackException();
else
currentContext = parentContext;
}
////////////////////////////////////////////////////////////////////
// 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 java.lang.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(java.lang.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 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 {
////////////////////////////////////////////////////////////////
// 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;
private Context child = null;
/**
* Create a new Namespace context.
*/
Context (Context parent)
{
if(parent==null)
{
prefixTable = new Hashtable();
uriTable = new Hashtable();
elementNameTable=new Hashtable();
attributeNameTable=new Hashtable();
}
else
setParent(parent);
}
/**
* @returns The child Namespace context object, or null if this
* is the last currently on the chain.
*/
Context getChild()
{
return child;
}
/**
* @returns The parent Namespace context object, or null if this
* is the root.
*/
Context getParent()
{
return parent;
}
/**
* (Re)set the parent of this Namespace context.
* This is separate from the c'tor because it's re-applied
* when a Context is reused by push-after-pop.
*
* @param context The parent Namespace context object.
*/
void setParent (Context parent)
{
this.parent = parent;
parent.child = this; // JJK: Doubly-linked
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 org.xml.sax.helpers.NamespaceSupport2#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 org.xml.sax.helpers.NamespaceSupport2#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 org.xml.sax.helpers.NamespaceSupport2#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 org.xml.sax.helpers.NamespaceSupport2#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 org.xml.sax.helpers.NamespaceSupport2#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 org.xml.sax.helpers.NamespaceSupport2#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 ()
{
// Start by copying our parent's bindings
prefixTable = (Hashtable)prefixTable.clone();
uriTable = (Hashtable)uriTable.clone();
// Replace the caches with empty ones, rather than
// trying to determine which should be flushed.
elementNameTable=new Hashtable();
attributeNameTable=new Hashtable();
tablesDirty = true;
}
}
}
// end of NamespaceSupport2.java
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