net.sf.saxon.event.NamespaceDifferencer Maven / Gradle / Ivy
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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2018-2023 Saxonica Limited
// This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0.
// If a copy of the MPL was not distributed with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
// This Source Code Form is "Incompatible With Secondary Licenses", as defined by the Mozilla Public License, v. 2.0.
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
package net.sf.saxon.event;
import net.sf.saxon.s9api.Location;
import net.sf.saxon.lib.SaxonOutputKeys;
import net.sf.saxon.om.*;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.type.SchemaType;
import java.util.Properties;
import java.util.Stack;
/**
* NamespaceDifferencer is a {@link ProxyReceiver} responsible for removing duplicate namespace
* declarations. It also ensures that namespace undeclarations are emitted when necessary.
*
* The NamespaceDifferencer assumes that in the input event stream, all in-scope namespaces for every element
* are accounted for in the call on namespace(). In the output event stream, the namespace() call represents
* namespace declarations rather than in-scope namespaces. So (a) redundant namespaces are removed,
* and (b) namespace undeclarations are added where necessary. A namespace undeclaration for the default
* namespace is always added if the parent element has a default namespace and the child element does not;
* namespace undeclarations for other namespaces are emitted only when the serialization option undeclare-namespaces
* is set.
*
* The {@code NamespaceDifferencer} is part of the serialization pipeline, responsible for translating result trees
* to serialized XML. As such, it is not concerned with operations such as namespace fixup and namespace
* inheritance that are part of the result tree construction process.
*
* The {@code NamespaceDifferencer} is also needed when writing output to tree models such as DOM and JDOM
* that require local namespace declarations to be provided for each element node.
*/
public class NamespaceDifferencer extends ProxyReceiver {
private boolean undeclareNamespaces = false;
private final Stack namespaceStack = new Stack<>();
private NodeName currentElement;
/**
* Create a NamespaceDeclarer
*
* @param next the Receiver to which events will be passed after namespace reduction
*/
public NamespaceDifferencer(Receiver next, Properties details) {
super(next);
undeclareNamespaces = "yes".equals(details.getProperty(SaxonOutputKeys.UNDECLARE_PREFIXES));
namespaceStack.push(NamespaceMap.emptyMap());
}
/**
* startElement. This call removes redundant namespace declarations, and
* possibly adds an xmlns="" undeclaration.
*/
@Override
public void startElement(NodeName elemName, SchemaType type,
AttributeMap attributes, NamespaceMap namespaces,
Location location, int properties)
throws XPathException {
currentElement = elemName;
NamespaceMap parentMap = namespaceStack.peek();
namespaceStack.push(namespaces);
NamespaceMap delta = getDifferences(namespaces, parentMap, currentElement.hasURI(NamespaceUri.NULL));
nextReceiver.startElement(elemName, type, attributes, delta, location, properties);
}
@Override
public void endElement() throws XPathException {
namespaceStack.pop();
super.endElement();
}
private NamespaceMap getDifferences(NamespaceMap thisMap, NamespaceMap parentMap, boolean elementInDefaultNamespace) throws XPathException {
if (thisMap != parentMap) {
NamespaceMap delta = NamespaceDeltaMap.emptyMap();
for (NamespaceBinding nb : thisMap) {
NamespaceUri parentUri = parentMap.getNamespaceUri(nb.getPrefix());
if (parentUri == null) {
delta = delta.put(nb.getPrefix(), nb.getNamespaceUri());
} else if (!parentUri.equals(nb.getNamespaceUri())) {
delta = delta.put(nb.getPrefix(), nb.getNamespaceUri());
}
}
if (undeclareNamespaces) {
for (NamespaceBinding nb : parentMap) {
if (thisMap.getNamespaceUri(nb.getPrefix()) == null) {
delta = delta.put(nb.getPrefix(), NamespaceUri.NULL);
}
}
} else {
// undeclare the default namespace if the parent element has a default namespace and the child does not
// See also bug 4696, test
if (!parentMap.getDefaultNamespace().isEmpty() &&
thisMap.getDefaultNamespace().isEmpty()) {
delta = delta.put("", NamespaceUri.NULL);
}
}
return delta;
}
return NamespaceMap.emptyMap();
}
}