Java example source code file (NamespaceSupport2.java)
The NamespaceSupport2.java Java example source code/*
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/*
* Copyright 1999-2004 The Apache Software Foundation.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/*
* $Id: NamespaceSupport2.java,v 1.3 2005/09/28 13:49:20 pvedula Exp $
*/
package com.sun.org.apache.xml.internal.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 Context2 currentContext; // Current point on the double-linked stack
////////////////////////////////////////////////////////////////////
// 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";
////////////////////////////////////////////////////////////////////
// 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 ()
{
// 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 Context2(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.
Context2 parentContext=currentContext;
currentContext = parentContext.getChild();
if (currentContext == null){
currentContext = new Context2(parentContext);
}
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 ()
{
Context2 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 not 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]
* <dd>The Namespace URI, or an empty string if none is
* in use.</dd>
* <dt>parts[1]
* <dd>The local name (without prefix).
* <dt>parts[2]
* <dd>The original raw name.
* </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 A string 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[] name=currentContext.processName(qName, isAttribute);
if(name==null)
return null;
// JJK: This recopying is required because processName may return
// a cached result. I Don't Like It. *****
System.arraycopy(name,0,parts,0,3);
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>Note: 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>Note: 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.
* @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>Note: the empty (default) prefix is
* <em>never 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)
{
// JJK: The old code involved creating a vector, filling it
// with all the matching prefixes, and then getting its
// elements enumerator. Wastes storage, wastes cycles if we
// don't actually need them all. Better to either implement
// a specific enumerator for these prefixes... or a filter
// around the all-prefixes enumerator, which comes out to
// roughly the same thing.
//
// **** Currently a filter. That may not be most efficient
// when I'm done restructuring storage!
return new PrefixForUriEnumerator(this,uri,getPrefixes());
}
/**
* 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();
}
}
////////////////////////////////////////////////////////////////////
// Local classes.
// These were _internal_ classes... but in fact they don't have to be,
// and may be more efficient if they aren't.
////////////////////////////////////////////////////////////////////
/**
* Implementation of Enumeration filter, wrapped
* aroung the get-all-prefixes version of the operation. This is NOT
* necessarily the most efficient approach; finding the URI and then asking
* what prefixes apply to it might make much more sense.
*/
class PrefixForUriEnumerator implements Enumeration
{
private Enumeration allPrefixes;
private String uri;
private String lookahead=null;
private NamespaceSupport2 nsup;
// Kluge: Since one can't do a constructor on an
// anonymous class (as far as I know)...
PrefixForUriEnumerator(NamespaceSupport2 nsup,String uri, Enumeration allPrefixes)
{
this.nsup=nsup;
this.uri=uri;
this.allPrefixes=allPrefixes;
}
public boolean hasMoreElements()
{
if(lookahead!=null)
return true;
while(allPrefixes.hasMoreElements())
{
String prefix=(String)allPrefixes.nextElement();
if(uri.equals(nsup.getURI(prefix)))
{
lookahead=prefix;
return true;
}
}
return false;
}
public Object nextElement()
{
if(hasMoreElements())
{
String tmp=lookahead;
lookahead=null;
return tmp;
}
else
throw new java.util.NoSuchElementException();
}
}
/**
* 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 Context2 {
////////////////////////////////////////////////////////////////
// Manefest Constants
////////////////////////////////////////////////////////////////
/**
* An empty enumeration.
*/
private final static Enumeration EMPTY_ENUMERATION =
new Vector().elements();
////////////////////////////////////////////////////////////////
// Protected state.
////////////////////////////////////////////////////////////////
Hashtable prefixTable;
Hashtable uriTable;
Hashtable elementNameTable;
Hashtable attributeNameTable;
String defaultNS = null;
////////////////////////////////////////////////////////////////
// Internal state.
////////////////////////////////////////////////////////////////
private Vector declarations = null;
private boolean tablesDirty = false;
private Context2 parent = null;
private Context2 child = null;
/**
* Create a new Namespace context.
*/
Context2 (Context2 parent)
{
if(parent==null)
{
prefixTable = new Hashtable();
uriTable = new Hashtable();
elementNameTable=null;
attributeNameTable=null;
}
else
setParent(parent);
}
/**
* @returns The child Namespace context object, or null if this
* is the last currently on the chain.
*/
Context2 getChild()
{
return child;
}
/**
* @returns The parent Namespace context object, or null if this
* is the root.
*/
Context2 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 Context2 is reused by push-after-pop.
*
* @param parent The parent Namespace context object.
*/
void setParent (Context2 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) {
if(elementNameTable==null)
elementNameTable=new Hashtable();
table = elementNameTable;
} else {
if(attributeNameTable==null)
attributeNameTable=new Hashtable();
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 not
* 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. In that case,
* the Context2 will share data structures with its parent.
* New tables are obtained only when new declarations are issued,
* so they can be popped off the stack.</p>
*
* <p> JJK: **** Alternative: each Context2 might declare
* _only_ its local bindings, and delegate upward if not found.</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 bindings should be flushed.
// As far as I can tell, these caches are never actually
// used in Xalan... More efficient to remove the whole
// cache system? ****
if(elementNameTable!=null)
elementNameTable=new Hashtable();
if(attributeNameTable!=null)
attributeNameTable=new Hashtable();
tablesDirty = true;
}
}
// end of NamespaceSupport2.java
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