/*
* Copyright 2003-2004 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: NamespaceMappings.java,v 1.6 2004/02/17 04:18:18 minchau Exp $
*/
package com.sun.org.apache.xml.internal.serializer;
import java.util.Enumeration;
import java.util.Hashtable;
import java.util.Stack;
import org.xml.sax.ContentHandler;
import org.xml.sax.SAXException;
/**
* This class keeps track of the currently defined namespaces. Conceptually the
* prefix/uri/depth triplets are pushed on a stack pushed on a stack. The depth
* indicates the nesting depth of the element for which the mapping was made.
*
* <p>For example:
* <pre>
* <chapter xmlns:p1="def">
* <paragraph xmlns:p2="ghi">
* <sentance xmlns:p3="jkl">
* </sentance>
* </paragraph>
* <paragraph xlmns:p4="mno">
* </paragraph>
* </chapter>
* </pre>
*
* When the <chapter> element is encounted the prefix "p1" associated with uri
* "def" is pushed on the stack with depth 1.
* When the first <paragraph> is encountered "p2" and "ghi" are pushed with
* depth 2.
* When the <sentance> is encountered "p3" and "jkl" are pushed with depth 3.
* When </sentance> occurs the popNamespaces(3) will pop "p3"/"jkl" off the
* stack. Of course popNamespaces(2) would pop anything with depth 2 or
* greater.
*
* So prefix/uri pairs are pushed and poped off the stack as elements are
* processed. At any given moment of processing the currently visible prefixes
* are on the stack and a prefix can be found given a uri, or a uri can be found
* given a prefix.
*/
public class NamespaceMappings
{
/**
* This member is continually incremented when new prefixes need to be
* generated. ("ns0" "ns1" ...)
*/
private int count = 0;
/**
* Stack of prefixes that have mappings
* The top of this stack is the prefix that was last mapped to an URI
*
* For every prefix pushed on this stack a corresponding integer is pushed
* on the m_nodeStack. That way all prefixes pushed at the current depth can
* be removed at the same time.
*/
private java.util.Stack m_prefixStack = new Stack();
/**
* Each entry (prefix) in this hashtable points to a Stack of URIs
*/
private Hashtable m_namespaces = new Hashtable();
/**
* The top of this stack contains the nested element depth
* of the last declared a namespace.
* Used to know how many prefix mappings to pop when leaving
* the current element depth.
* For every prefix mapping the current element depth is
* pushed on this stack, as well as the prefix on the m_prefixStack
* That way all prefixes pushed at the current depth can be
* removed at the same time.
* Used to ensure prefix/uri map scopes are closed correctly
*
*/
private Stack m_nodeStack = new Stack();
private static final String EMPTYSTRING = "";
private static final String XML_PREFIX = "xml"; // was "xmlns"
/**
* Default constructor
* @see java.lang.Object#Object()
*/
public NamespaceMappings()
{
initNamespaces();
}
/**
* This method initializes the namespace object with appropriate stacks
* and predefines a few prefix/uri pairs which always exist.
*/
private void initNamespaces()
{
// Define the default namespace (initially maps to "" uri)
Stack stack;
m_namespaces.put(EMPTYSTRING, stack = new Stack());
stack.push(EMPTYSTRING);
m_prefixStack.push(EMPTYSTRING);
m_namespaces.put(XML_PREFIX, stack = new Stack());
stack.push("http://www.w3.org/XML/1998/namespace");
m_prefixStack.push(XML_PREFIX);
m_nodeStack.push(new Integer(-1));
}
/**
* Use a namespace prefix to lookup a namespace URI.
*
* @param prefix String the prefix of the namespace
* @return the URI corresponding to the prefix
*/
public String lookupNamespace(String prefix)
{
final Stack stack = (Stack) m_namespaces.get(prefix);
return stack != null && !stack.isEmpty() ? (String) stack.peek() : null;
}
/**
* Given a namespace uri, and the namespaces mappings for the
* current element, return the current prefix for that uri.
*
* @param uri the namespace URI to be search for
* @return an existing prefix that maps to the given URI, null if no prefix
* maps to the given namespace URI.
*/
public String lookupPrefix(String uri)
{
String foundPrefix = null;
Enumeration prefixes = m_namespaces.keys();
while (prefixes.hasMoreElements())
{
String prefix = (String) prefixes.nextElement();
String uri2 = lookupNamespace(prefix);
if (uri2 != null && uri2.equals(uri))
{
foundPrefix = prefix;
break;
}
}
return foundPrefix;
}
/**
* Undeclare the namespace that is currently pointed to by a given prefix
*/
public boolean popNamespace(String prefix)
{
// Prefixes "xml" and "xmlns" cannot be redefined
if (prefix.startsWith(XML_PREFIX))
{
return false;
}
Stack stack;
if ((stack = (Stack) m_namespaces.get(prefix)) != null)
{
stack.pop();
return true;
}
return false;
}
/**
* Declare a prefix to point to a namespace URI
* @param prefix a String with the prefix for a qualified name
* @param uri a String with the uri to which the prefix is to map
* @param elemDepth the depth of current declaration
*/
public boolean pushNamespace(String prefix, String uri, int elemDepth)
{
// Prefixes "xml" and "xmlns" cannot be redefined
if (prefix.startsWith(XML_PREFIX))
{
return false;
}
Stack stack;
// Get the stack that contains URIs for the specified prefix
if ((stack = (Stack) m_namespaces.get(prefix)) == null)
{
m_namespaces.put(prefix, stack = new Stack());
}
if (!stack.empty() && uri.equals(stack.peek()))
{
return false;
}
stack.push(uri);
m_prefixStack.push(prefix);
m_nodeStack.push(new Integer(elemDepth));
return true;
}
/**
* Pop, or undeclare all namespace definitions that are currently
* declared at the given element depth, or deepter.
* @param elemDepth the element depth for which mappings declared at this
* depth or deeper will no longer be valid
* @param saxHandler The ContentHandler to notify of any endPrefixMapping()
* calls. This parameter can be null.
*/
public void popNamespaces(int elemDepth, ContentHandler saxHandler)
{
while (true)
{
if (m_nodeStack.isEmpty())
return;
Integer i = (Integer) (m_nodeStack.peek());
if (i.intValue() < elemDepth)
return;
/* the depth of the declared mapping is elemDepth or deeper
* so get rid of it
*/
m_nodeStack.pop();
final String prefix = (String) m_prefixStack.pop();
popNamespace(prefix);
if (saxHandler != null)
{
try
{
saxHandler.endPrefixMapping(prefix);
}
catch (SAXException e)
{
// not much we can do if they aren't willing to listen
}
}
}
}
/**
* Generate a new namespace prefix ( ns0, ns1 ...) not used before
* @return String a new namespace prefix ( ns0, ns1, ns2 ...)
*/
public String generateNextPrefix()
{
return "ns" + (count++);
}
/**
* This method makes a clone of this object.
*
*/
public Object clone() throws CloneNotSupportedException {
NamespaceMappings clone = new NamespaceMappings();
clone.m_prefixStack = (Stack)m_prefixStack.clone();
clone.m_nodeStack = (Stack) m_nodeStack.clone();
clone.m_namespaces = (Hashtable) m_namespaces.clone();
clone.count = count;
return clone;
}
public final void reset()
{
this.count = 0;
this.m_namespaces.clear();
this.m_nodeStack.clear();
this.m_prefixStack.clear();
initNamespaces();
}
}
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