/*
* Copyright (C) 2006, 2007, 2008 XStream Committers.
* All rights reserved.
*
* The software in this package is published under the terms of the BSD
* style license a copy of which has been included with this distribution in
* the LICENSE.txt file.
*
* Created on 15. March 2007 by Joerg Schaible
*/
package com.thoughtworks.xstream.core;
import com.thoughtworks.xstream.converters.ConversionException;
import com.thoughtworks.xstream.converters.Converter;
import com.thoughtworks.xstream.converters.ConverterLookup;
import com.thoughtworks.xstream.core.util.ObjectIdDictionary;
import com.thoughtworks.xstream.io.HierarchicalStreamWriter;
import com.thoughtworks.xstream.io.path.Path;
import com.thoughtworks.xstream.io.path.PathTracker;
import com.thoughtworks.xstream.io.path.PathTrackingWriter;
import com.thoughtworks.xstream.mapper.Mapper;
/**
* Abstract base class for a TreeMarshaller, that can build references.
*
* @author Joe Walnes
* @author Jörg Schaible
* @author Mauro Talevi
* @since 1.2
*/
public abstract class AbstractReferenceMarshaller extends TreeMarshaller {
private ObjectIdDictionary references = new ObjectIdDictionary();
private ObjectIdDictionary implicitElements = new ObjectIdDictionary();
private PathTracker pathTracker = new PathTracker();
private Path lastPath;
public AbstractReferenceMarshaller(HierarchicalStreamWriter writer,
ConverterLookup converterLookup,
Mapper mapper) {
super(writer, converterLookup, mapper);
this.writer = new PathTrackingWriter(writer, pathTracker);
}
public void convert(Object item, Converter converter) {
if (getMapper().isImmutableValueType(item.getClass())) {
// strings, ints, dates, etc... don't bother using references.
converter.marshal(item, writer, this);
} else {
Path currentPath = pathTracker.getPath();
Object existingReferenceKey = references.lookupId(item);
if (existingReferenceKey != null) {
String attributeName = getMapper().aliasForSystemAttribute("reference");
if (attributeName != null) {
writer.addAttribute(attributeName, createReference(currentPath, existingReferenceKey));
}
} else if (implicitElements.lookupId(item) != null) {
throw new ReferencedImplicitElementException(item, currentPath);
} else {
Object newReferenceKey = createReferenceKey(currentPath, item);
if (lastPath == null || !currentPath.isAncestor(lastPath)) {
fireValidReference(newReferenceKey);
lastPath = currentPath;
references.associateId(item, newReferenceKey);
} else {
implicitElements.associateId(item, newReferenceKey);
}
converter.marshal(item, writer, this);
}
}
}
protected abstract String createReference(Path currentPath, Object existingReferenceKey);
protected abstract Object createReferenceKey(Path currentPath, Object item);
protected abstract void fireValidReference(Object referenceKey);
public static class ReferencedImplicitElementException extends ConversionException {
/**
* @deprecated since 1.2.1
*/
public ReferencedImplicitElementException(final String msg) {
super(msg);
}
public ReferencedImplicitElementException(final Object item, final Path path) {
super("Cannot reference implicit element");
add("implicit-element", item.toString());
add("referencing-element", path.toString());
}
}
}