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The XSLT and XQuery Processor
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2018-2022 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.option.xom;
import net.sf.saxon.Configuration;
import net.sf.saxon.event.Builder;
import net.sf.saxon.event.PipelineConfiguration;
import net.sf.saxon.event.Receiver;
import net.sf.saxon.expr.JPConverter;
import net.sf.saxon.expr.PJConverter;
import net.sf.saxon.expr.XPathContext;
import net.sf.saxon.lib.ExternalObjectModel;
import net.sf.saxon.lib.NamespaceConstant;
import net.sf.saxon.om.*;
import net.sf.saxon.pattern.AnyNodeTest;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.tree.wrapper.VirtualNode;
import net.sf.saxon.type.ItemType;
import net.sf.saxon.value.SequenceExtent;
import nu.xom.Document;
import nu.xom.Node;
import javax.xml.transform.Result;
import javax.xml.transform.Source;
import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
/**
* This interface must be implemented by any third-party object model that can
* be wrapped with a wrapper that implements the Saxon Object Model (the NodeInfo interface).
* This implementation of the interface supports wrapping of JDOM Documents.
* This is a singleton class whose instance can be obtained using the {@link #getInstance}
* method. However, the constructor is public for backwards compatibility.
* The class extends {@link TreeModel} so that any interface expected a TreeModel, for example
* {@link net.sf.saxon.s9api.XdmDestination#setTreeModel}, can take XOMObjectModel.getInstance()
* as an argument.
*/
public class XOMObjectModel extends TreeModel implements ExternalObjectModel {
private static final XOMObjectModel THE_INSTANCE = new XOMObjectModel();
public static XOMObjectModel getInstance() {
return THE_INSTANCE;
}
public XOMObjectModel() {
}
/**
* Get the name of a characteristic class, which, if it can be loaded, indicates that the supporting libraries
* for this object model implementation are available on the classpath
*
* @return by convention (but not necessarily) the class that implements a document node in the relevant
* external model
*/
@Override
public String getDocumentClassName() {
return "nu.xom.Document";
}
/**
* Get the URI of the external object model as used in the JAXP factory interfaces for obtaining
* an XPath implementation
*/
@Override
public String getIdentifyingURI() {
return NamespaceConstant.OBJECT_MODEL_XOM;
}
@Override
public String getName() {
return "XOM";
}
@Override
public Builder makeBuilder(PipelineConfiguration pipe) {
return new XOMWriter(pipe);
}
/*@Nullable*/
@Override
public PJConverter getPJConverter(Class targetClass) {
if (isRecognizedNodeClass(targetClass)) {
return new PJConverter() {
@Override
public Object convert(Sequence value, Class targetClass, XPathContext context) throws XPathException {
return convertXPathValueToObject(value, targetClass);
}
};
} else {
return null;
}
}
@Override
public JPConverter getJPConverter(Class sourceClass, Configuration config) {
if (isRecognizedNodeClass(sourceClass)) {
return new JPConverter() {
@Override
public GroundedValue convert(Object object, XPathContext context) {
return convertObjectToXPathValue(object, context.getConfiguration());
}
@Override
public ItemType getItemType() {
return AnyNodeTest.getInstance();
}
};
} else {
return null;
}
}
/**
* Get a converter that converts a sequence of XPath nodes to this model's representation
* of a node list.
*
* @param node an example of the kind of node used in this model
* @return if the model does not recognize this node as one of its own, return null. Otherwise
* return a PJConverter that takes a list of XPath nodes (represented as NodeInfo objects) and
* returns a collection of nodes in this object model
*/
@Override
public PJConverter getNodeListCreator(Object node) {
return null;
}
/**
* Test whether this object model recognizes a given node as one of its own
*/
public boolean isRecognizedNode(Object object) {
return object instanceof Node;
}
/**
* Test whether this object model recognizes a given class as representing a
* node in that object model. This method will generally be called at compile time.
*
* @param nodeClass A class that possibly represents nodes
* @return true if the class is used to represent nodes in this object model
*/
public boolean isRecognizedNodeClass(Class nodeClass) {
return nu.xom.Node.class.isAssignableFrom(nodeClass);
}
/**
* Test whether this object model recognizes a particular kind of JAXP Result object,
* and if it does, return a Receiver that builds an instance of this data model from
* a sequence of events. If the Result is not recognized, return null.
* @return always null, because no XOM Result object is recognized
*/
@Override
public Receiver getDocumentBuilder(Result result) {
return null;
}
/**
* Wrap or unwrap a node using this object model to return the corresponding Saxon node. If the supplied
* source does not belong to this object model, return null
*/
@Override
public NodeInfo unravel(Source source, Configuration config) {
return null;
}
/**
* Convert a Java object to an XPath value. If the supplied object is recognized as a representation
* of a value using this object model, the object model should convert the value to an XPath value
* and return this as the result. If not, it should return null. If the object is recognized but cannot
* be converted, an exception should be thrown
*/
private GroundedValue convertObjectToXPathValue(Object object, Configuration config) {
if (object instanceof Node) {
return wrapNode((Node) object, config);
} else if (object instanceof Node[]) {
NodeInfo[] nodes = new NodeInfo[((Node[]) object).length];
for (int i = 0; i < nodes.length; i++) {
nodes[i] = wrapNode(((Node[]) object)[i], config);
}
return new SequenceExtent.Of<>(nodes);
} else {
return null;
}
}
private synchronized NodeInfo wrapNode(Node node, Configuration config) {
return new XOMDocumentWrapper(node.getDocument(), config).wrap(node);
}
/**
* Convert an XPath value to an object in this object model. If the supplied value can be converted
* to an object in this model, of the specified class, then the conversion should be done and the
* resulting object returned. If the value cannot be converted, the method should return null. Note
* that the supplied class might be a List, in which case the method should inspect the contents of the
* Value to see whether they belong to this object model.
*/
public Object convertXPathValueToObject(Sequence value, Class targetClass)
throws XPathException {
// We accept the object if (a) the target class is Node or Node[],
// or (b) the supplied object is a node, or sequence of nodes, that wrap XOM nodes,
// provided that the target class is Object or a collection class
boolean requireXOM =
Node.class.isAssignableFrom(targetClass) ||
(targetClass.isArray() && Node.class.isAssignableFrom(targetClass.getComponentType()));
// Note: we allow the declared type of the method argument to be a subclass of Node. If the actual
// node supplied is the wrong kind of node, this will result in a Java exception.
boolean allowXOM =
targetClass == Object.class || targetClass.isAssignableFrom(ArrayList.class) ||
targetClass.isAssignableFrom(HashSet.class) ||
(targetClass.isArray() && targetClass.getComponentType() == Object.class);
if (!(requireXOM || allowXOM)) {
return null;
}
List nodes = new ArrayList<>(20);
SequenceIterator iter = value.iterate();
while (true) {
Item item = iter.next();
if (item == null) {
break;
}
if (item instanceof VirtualNode) {
Object o = ((VirtualNode) item).getRealNode();
if (o instanceof Node) {
nodes.add((Node)o);
} else {
if (requireXOM) {
throw new XPathException("Extension function required class " + targetClass.getName() +
"; supplied value of class " + item.getClass().getName() +
" could not be converted");
}
}
} else if (requireXOM) {
throw new XPathException("Extension function required class " + targetClass.getName() +
"; supplied value of class " + item.getClass().getName() +
" could not be converted");
} else {
return null;
}
}
if (nodes.isEmpty() && !requireXOM) {
return null; // empty sequence supplied - try a different mapping
}
if (Node.class.isAssignableFrom(targetClass)) {
if (nodes.size() != 1) {
throw new XPathException("Extension function requires a single XOM Node" +
"; supplied value contains " + nodes.size() + " nodes");
}
return nodes.get(0);
} else if (targetClass.isArray() && Node.class.isAssignableFrom(targetClass.getComponentType())) {
Node[] array = (Node[]) Array.newInstance(targetClass.getComponentType(), nodes.size());
array = nodes.toArray(array);
return array;
} else if (targetClass.isAssignableFrom(ArrayList.class)) {
return nodes;
} else if (targetClass.isAssignableFrom(HashSet.class)) {
return new HashSet<>(nodes);
} else {
// after all this work, give up
return null;
}
}
/**
* Wrap a document node in the external object model in a document wrapper that implements
* the Saxon DocumentInfo interface
*
* @param node a node (any node) in the third party document
* @param config the Saxon configuration (which among other things provides access to the NamePool)
* @return the wrapper, which must implement DocumentInfo
*/
public TreeInfo wrapDocument(Object node, Configuration config) {
Document documentNode = ((Node) node).getDocument();
return new XOMDocumentWrapper(documentNode, config);
}
/**
* Wrap a node within the external object model in a node wrapper that implements the Saxon
* VirtualNode interface (which is an extension of NodeInfo)
*
* @param document the document wrapper, as a DocumentInfo object
* @param node the node to be wrapped. This must be a node within the document wrapped by the
* DocumentInfo provided in the first argument
* @return the wrapper for the node, as an instance of VirtualNode
*/
public NodeInfo wrapNode(TreeInfo document, Object node) {
if (!(node instanceof Node)) {
throw new IllegalArgumentException("Object to be wrapped is not a XOM Node: " + node.getClass());
}
return ((XOMDocumentWrapper) document).wrap((Node) node);
}
}