/*
* Copyright 2009 Google Inc.
*
* Licensed 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 com.google.devtools.depan.eclipse.persist;
import com.google.devtools.depan.graph.api.Relation;
import com.google.devtools.depan.graph.basic.BasicEdge;
import com.google.devtools.depan.model.GraphEdge;
import com.google.devtools.depan.model.GraphModel;
import com.google.devtools.depan.model.GraphNode;
import com.thoughtworks.xstream.converters.Converter;
import com.thoughtworks.xstream.converters.MarshallingContext;
import com.thoughtworks.xstream.converters.UnmarshallingContext;
import com.thoughtworks.xstream.io.HierarchicalStreamReader;
import com.thoughtworks.xstream.io.HierarchicalStreamWriter;
import com.thoughtworks.xstream.mapper.Mapper;
/**
* {@code XStream} converter to handle {@code GraphEdge}s. This converter
* assumes that the {@code UnmarshallingContext} as an {@code GraphModel} entry
* that can be retrieved by the {@code GraphModel.class} key.
*
* @author <a href="mailto:leeca@google.com">Lee Carver</a>
*/
public class EdgeReferenceConverter implements Converter {
public static final String EDGE_REF_TAG = "edge-ref";
private static final String RELATION_TAG = "relation";
private static final String HEAD_TAG = "head";
private static final String TAIL_TAG = "tail";
private final Mapper mapper;
/** Source of information about known edges and nodes. */
private final ViewDocumentConverter viewConverter;
public EdgeReferenceConverter(
Mapper mapper, ViewDocumentConverter viewConverter) {
this.mapper = mapper;
this.viewConverter = viewConverter;
}
@Override
@SuppressWarnings("rawtypes") // Parent type uses raw type Class
public boolean canConvert(Class type) {
return GraphEdge.class.isAssignableFrom(type);
}
@Override
public void marshal(Object source, HierarchicalStreamWriter writer,
MarshallingContext context) {
GraphEdge edge = (GraphEdge) source;
Relation relation = edge.getRelation();
writer.startNode(RELATION_TAG);
Class<?> actualType = relation.getClass();
Class<?> defaultType = mapper.defaultImplementationOf(BasicEdge.class);
if (!actualType.equals(defaultType)) {
writer.addAttribute(
mapper.aliasForAttribute("class"),
mapper.serializedClass(actualType));
}
context.convertAnother(relation);
writer.endNode();
writer.startNode(HEAD_TAG);
context.convertAnother(edge.getHead().getId());
writer.endNode();
writer.startNode(TAIL_TAG);
context.convertAnother(edge.getTail().getId());
writer.endNode();
}
/**
* {@inheritDoc}
* <p>
* This implementation assumes that a {@code GraphModel}, used to find nodes,
* can be retrieved from the {@code UnmarshallingContext} with the key
* {@code GraphModel.class}.
*/
@Override
public Object unmarshal(HierarchicalStreamReader reader,
UnmarshallingContext context) {
try {
GraphModel graph = viewConverter.getGraphModel(context);
reader.moveDown();
Relation relation = unmarshallRelation(reader, context);
reader.moveUp();
reader.moveDown();
GraphNode head = unmarshallGraphNode(reader, context, graph);
reader.moveUp();
reader.moveDown();
GraphNode tail = unmarshallGraphNode(reader, context, graph);
reader.moveUp();
GraphEdge result = (GraphEdge) graph.findEdge(relation, head, tail);
return result;
} catch (RuntimeException err) {
// TODO(leeca): Add some error diagnostics, or eliminate as dead code.
throw err;
}
}
private Relation unmarshallRelation(
HierarchicalStreamReader reader, UnmarshallingContext context) {
String classAttribute =
reader.getAttribute(mapper.aliasForAttribute("class"));
Class<?> resultClass = mapper.realClass(classAttribute);
Relation relation = (Relation) context.convertAnother(null, resultClass);
return relation;
}
private GraphNode unmarshallGraphNode(
HierarchicalStreamReader reader, UnmarshallingContext context,
GraphModel graph) {
String nodeId = reader.getValue();
GraphNode result = (GraphNode) graph.findNode(nodeId);
if (null == result) {
throw new IllegalStateException(
"Edge reference to undefined node " + nodeId);
}
return result;
}
}