org.apache.ode.utils.NamespaceStack Maven / Gradle / Ivy
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* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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.
*/
package org.apache.ode.utils;
import java.util.EmptyStackException;
import java.util.HashMap;
import java.util.Iterator;
import javax.xml.namespace.QName;
import org.xml.sax.ContentHandler;
import org.xml.sax.SAXException;
/**
*
* This is a utility for a SAX ContentHandler implementation to use in
* tracking namespace declarations during a parse. The assumption is that the
* handler has access to the full stream of events relevant to managing the
* declarations. The primary use case is the resolution of Strings,
* e.g., from attribute values or element content, to QName objects.
*
*/
public class NamespaceStack {
private Frame _current;
/**
*
* Construct a new instance with the bare minimum bindings for the
* xmlns, xml, and empty prefixes. Note that the empty
* prefix is bound to the empty (non-null) URI.
*
*/
public NamespaceStack() {
_current = new Frame();
/*
* As per the Namespaces in XML Errata:
* http://www.w3.org/XML/xml-names-19990114-errata
*/
_current.declarePrefix("xmlns","http://www.w3.org/2000/xmlns/");
/*
* As per the Namespaces in XML Rec:
* http://www.w3.org/TR/1999/REC-xml-names-19990114
*/
_current.declarePrefix("xml","http://www.w3.org/XML/1998/namespace");
/*
* As per the Namespaces in XML Rec:
* http://www.w3.org/TR/1999/REC-xml-names-19990114
*/
_current.declarePrefix("","");
}
/**
*
* Convert the current stack of contexts into a single NSContext.
*
* @return the NSContext instance
*/
public NSContext toNSContext() {
NSContext n = new NSContext();
for (Frame f = _current;f != null; f=f._parent) {
if (f._bindings == null) continue;
for (Iterator it = f._bindings.keySet().iterator();it.hasNext();) {
String pfx = (String) it.next();
if (n.getNamespaceURI(pfx) == null) {
n.register(pfx, f._bindings.get(pfx));
}
}
}
return n;
}
/**
*
* Push a fresh context onto the stack. This method should be called somewhere in
* the body of a startElement(), as it represents the namespace
* resolution context for the events that occur between that event and the
* corresponding endElement().
*
* @see org.xml.sax.ContentHandler
*/
public void pushNewContext() {
_current = new Frame(_current);
}
/**
*
* Pop a context from the stack. This method should be called somewhere in the
* body of an endElement, as it clears the context that was used for
* namespace resolution within the body of the corresponding element.
*
* @see org.xml.sax.ContentHandler
*/
public void pop() {
if (_current._parent == null) {
throw new EmptyStackException();
}
_current = _current._parent;
}
/**
*
* Declare a new prefix binding. This binding will supercede a binding with the
* same prefix in the same scope. As a crutch, null arguments may be
* passed and will be interpreted as "". Note that binding
* a non-empty prefix to an empty URI is not permitted in XML 1.0 but is not
* flagged as an error by the method.
*
* @param prefix the prefix to bind
* @param uri the URI to bind it to
*/
public void declarePrefix(String prefix, String uri) {
_current.declarePrefix(prefix==null?"":prefix, uri==null?"":uri);
}
/**
*
* Retrieve the URI bound to the supplied prefix or null if no URI
* is bound to the supplied prefix. As a crutch, a null argument
* may be passed and will be interpreted as the empty prefix
* ("").
*
* @returns the URI or null if no URI is bound.
*/
public String getNamespaceUri(String prefix) {
return _current.getNamespaceURI(prefix==null?"":prefix);
}
/**
*
* Fire the events for the current frame's prefixes into a ContentHandler.
*
* @param ch the target ContentHandler
* @throws SAXException if the target method does.
*/
public void startPrefixMappings(ContentHandler ch) throws SAXException {
_current.startPrefixMappings(ch);
}
/**
*
* Fire the events for the current frame's prefixes into a ContentHandler.
*
* @param ch the target ContentHandler.
* @throws SAXException if the target method does.
*/
public void endPrefixMappings(ContentHandler ch) throws SAXException {
_current.endPrefixMappings(ch);
}
/**
*
* Allocate and declare a new namespace prefix for the current context that uses
* the supplied "hint" as a start. The algorithm used will defer to an
* existing binding, then try the hint, then use a variant of the hint until it
* finds an available prefix.
*
* @param hint a hint as to the desired prefix or null if any prefix
* will do.
* @param uri the URI to bind to the prefix.
* @return the suggested prefix.
*/
public String allocatePrefix(String hint, String uri) {
String pfx = getPrefix(uri);
if (pfx == null) {
hint = hint==null?"ns":hint;
String u = getNamespaceUri(hint);
if (u == null) {
declarePrefix(hint,uri);
pfx = hint;
} else if (u.equals(uri)) {
pfx = hint;
} else {
// ??
}
}
return pfx;
}
public String getPrefix(String uri) {
return toNSContext().getPrefix(uri);
}
/**
*
* Derference the prefix on a QName in String form and return a Java
* QName object.
*
* @param qname the QName in string form.
* @return the dereferenced QName.
* @throws IllegalArgumentException if a null argument is passed,
* a malformed argument (e.g., :foo or foo:) is passed,
* or if the prefix cannot be resolved to a URI.
*/
public QName dereferenceQName(String qname) {
if (qname == null) {
throw new IllegalArgumentException("Unable to dereference as a QName.");
}
int pos = qname.indexOf(':');
QName qn;
if (pos == qname.length() - 1 || pos == 0) {
throw new IllegalArgumentException("\"" + qname + "\" is a malformed QName.");
} else if (pos == -1) {
qn = new QName (getNamespaceUri(""),qname);
} else {
String uri = getNamespaceUri(qname.substring(0,pos));
if (uri == null) {
throw new IllegalArgumentException("No URI is bound to " +
qname.substring(0,pos) + ".");
}
qn = new QName(uri,qname.substring(pos+1));
}
return qn;
}
private class Frame {
Frame _parent;
HashMap _bindings;
Frame() {
// This space intentionally left blank.
}
Frame(Frame parent) {
_parent = parent;
}
void startPrefixMappings(ContentHandler ch) throws SAXException {
if (_bindings != null) {
for(Iterator it = _bindings.keySet().iterator();it.hasNext();) {
String prefix = (String) it.next();
ch.startPrefixMapping(prefix, _bindings.get(prefix));
}
}
}
void endPrefixMappings(ContentHandler ch) throws SAXException {
if (_bindings != null) {
for (Iterator it = _bindings.keySet().iterator();it.hasNext();) {
ch.endPrefixMapping((String) it.next());
}
}
}
void declarePrefix(String prefix, String uri) {
if (_bindings == null) {
_bindings = new HashMap();
}
_bindings.put(prefix,uri);
}
String getPrefix(String uri) {
return "";
}
String getNamespaceURI(String prefix) {
String uri = null;
if (_bindings != null) {
uri = _bindings.get(prefix);
}
if (uri == null) {
uri= _parent==null ? null:(_parent.getNamespaceURI(prefix));
}
return uri;
}
}
}