/*
* Javolution - Java(TM) Solution for Real-Time and Embedded Systems
* Copyright (C) 2006 - Javolution (http://javolution.org/)
* All rights reserved.
*
* Permission to use, copy, modify, and distribute this software is
* freely granted, provided that this notice is preserved.
*/
package javolution.xml;
import java.lang.CharSequence;
import javolution.lang.Reusable;
import javolution.text.CharArray;
import javolution.text.TextBuilder;
import javolution.util.FastComparator;
import javolution.util.FastMap;
import javolution.util.FastTable;
import javolution.util.Index;
import javolution.xml.stream.XMLStreamException;
/**
* <p> This class represents a resolver for XML cross references during
* the marshalling/unmarshalling process.</p>
*
* <p> Instances of this class may only be shared by {@link XMLObjectReader}/
* {@link XMLObjectWriter} running sequentially (for cross references
* spawning multiple documents).</p>
*
* @author <a href="mailto:jean-marie@dautelle.com">Jean-Marie Dautelle</a>
* @version 4.0, September 4, 2006
*/
public class XMLReferenceResolver implements Reusable {
/**
* Holds object to identifier (FastTable.Index) mapping.
*/
private FastMap _objectToId = new FastMap()
.setKeyComparator(FastComparator.IDENTITY);
/**
* Holds the objects (index to object mapping).
*/
private FastTable _idToObject = new FastTable();
/**
* Holds the id counter.
*/
private int _counter;
/**
* Holds the identifier attribute name.
*/
private String _idName = "id";
/**
* Holds the identifier attribute URI if any.
*/
private String _idURI = null;
/**
* Holds the reference attribute name.
*/
private String _refName = "ref";
/**
* Holds the reference attribute URI if any.
*/
private String _refURI = null;
/**
* Default constructor.
*/
public XMLReferenceResolver() {
}
/**
* Sets the name of the identifier attribute (by default<code>"id"</code>).
* If the name is <code>null</code> then the identifier attribute
* is never read/written (which may prevent unmarshalling).
*
* @param name the name of the attribute or <code>null</code>.
*/
public void setIdentifierAttribute(String name) {
setIdentifierAttribute(name, null);
}
/**
* Sets the local name and namespace URI of the identifier attribute.
*
* @param localName the local name of the attribute or <code>null</code>.
* @param uri the URI of the attribute or <code>null</code> if the attribute
* has no namespace URI.
*/
public void setIdentifierAttribute(String localName, String uri) {
_idName = localName;
_idURI = uri;
}
/**
* Sets the name of the reference attribute (by default<code>"ref"</code>).
* If the name is <code>null</code> then the reference attribute
* is never read/written (which may prevent unmarshalling).
*
* @param name the name of the attribute or <code>null</code>.
*/
public void setReferenceAttribute(String name) {
setReferenceAttribute(name, null);
}
/**
* Sets the local name and namespace URI of the identifier attribute.
*
* @param localName the local name of the attribute or <code>null</code>.
* @param uri the URI of the attribute or <code>null</code> if the attribute
* has no namespace URI.
*/
public void setReferenceAttribute(String localName, String uri) {
_refName = localName;
_refURI = uri;
}
/**
* Writes a reference to the specified object into the specified XML
* element. The default implementation writes the reference into the
* reference attribute and for the first occurences an identifier
* (counter starting at 1) is written into the identifier attribute.
*
* @param obj the object for which the reference is written.
* @param xml the output XML element.
* @return <code>true</code> if a reference is written;
* <code>false</code> if a new identifier is written.
*/
public boolean writeReference(Object obj, XMLFormat.OutputElement xml)
throws XMLStreamException {
Index id = (Index) _objectToId.get(obj);
if (id == null) { // New identifier.
id = Index.valueOf(_counter++);
_objectToId.put(obj, id);
_tmp.clear().append(id.intValue());
if (_idURI == null) {
xml.getStreamWriter().writeAttribute(toCsq(_idName),
_tmp);
} else {
xml.getStreamWriter().writeAttribute(toCsq(_idURI),
toCsq(_idName), _tmp);
}
return false;
}
_tmp.clear().append(id.intValue());
if (_refURI == null) {
xml._writer
.writeAttribute(toCsq(_refName), _tmp);
} else {
xml._writer.writeAttribute(toCsq(_refURI),
toCsq(_refName), _tmp);
}
return true;
}
private TextBuilder _tmp = new TextBuilder();
/**
* Reads the object referenced by the specified xml input element if any.
* The default implementation reads the reference attribute to retrieve
* the object.
*
* @param xml the input XML element.
* @return the referenced object or <code>null</code> if the specified
* XML input does not have a reference attribute.
*/
public Object readReference(XMLFormat.InputElement xml)
throws XMLStreamException {
CharArray value = xml._reader.getAttributeValue(
toCsq(_refURI), toCsq(_refName));
if (value == null)
return null;
int ref = value.toInt();
if (ref >= _idToObject.size())
throw new XMLStreamException("Reference: " + value + " not found");
return _idToObject.get(ref);
}
/**
* Creates a reference for the specified object (the identifier
* being specified by the input XML element).
* The default implementation reads the identifier attribute (if any)
* and associates it to the specified object.
*
* @param obj the object being referenced.
* @param xml the input XML element holding the reference identifier.
*/
public void createReference(Object obj, XMLFormat.InputElement xml)
throws XMLStreamException {
CharArray value = xml._reader.getAttributeValue(
toCsq(_idURI), toCsq(_idName));
if (value == null)
return;
int i = value.toInt();
if (_idToObject.size() != i)
throw new XMLStreamException("Identifier discontinuity detected "
+ "(expected " + _idToObject.size() + " found " + i + ")");
_idToObject.add(obj);
}
// Implements Reusable.
public void reset() {
_idName = "id";
_idURI = null;
_refName = "ref";
_refURI = null;
_idToObject.clear();
_objectToId.clear();
_counter = 0;
}
private static CharSequence toCsq/**/(Object str) {
return QName.j2meToCharSeq(str);
}
}