/*
* 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.eclipse.plugins.SourcePluginRegistry;
import com.thoughtworks.xstream.XStream;
import com.thoughtworks.xstream.io.xml.StaxDriver;
/**
* Generate {@code XStream} instances that are configured for DepAn. The DepAn
* configuration include support class loading from plugins, basic
* {@code GraphModel}s and {@code GraphEdge}s, and all node and relations types
* from all active plugins.
* <p>
* If you need custom configuration of an {@code XStream} instance, you can
* construct it yourself and then configure it with
* {@link #configureXStream(XStream)}.
*
* @author <a href="mailto:leeca@google.com">Lee Carver</a>
*/
public class XStreamFactory {
/**
* Sharable {@code XStream}, suitable for persistence of {@code GraphModel}s.
*/
private static XStream sharedGraphXStream;
/**
* Sharable {@code XStream}, suitable for persistence with references to
* {@code GraphModel} elements.
*/
private static XStream sharedRefXStream;
/**
* Prevent instantiation of this namespace class
*/
private XStreamFactory() {
}
/**
* Interface for objects that need to configure properties of the
* {@code XStream} instances.
*/
public interface Config {
void config(XStream xstream);
}
/**
* Provide a shared XStream instance that is initialized to use the StAX
* XML parser and to persist {@code GraphModel}s. This can be used to avoid
* expensive configuration processes of separate XStreams, but no added
* configuration changes should be made.
*
* @return XStream configured for persistence of {@code GraphModel}s.
*/
public static synchronized XStream getSharedGraphXStream() {
if (null == sharedGraphXStream) {
sharedGraphXStream = newStaxXStream();
configureGraphXStream(sharedGraphXStream);
}
return sharedGraphXStream;
}
/**
* Provide a shared XStream instance that is initialized to use the StAX
* XML parser and to persist references to {@code GraphModel} elements..
* This can be used to avoid expensive configuration processes of separate
* XStreams, but no added configuration changes should be made.
*
* @return XStream configured for references to {@code GraphModel} elements.
*/
public static synchronized XStream getSharedRefXStream() {
if (null == sharedRefXStream) {
sharedRefXStream = newStaxXStream();
configureRefXStream(sharedRefXStream);
}
return sharedRefXStream;
}
/**
* Provide an XStream instance that is initialized to use the StAX XML
* toolkit. The returned instance will still need to be configured
* for DepAn.
*
* @return StAX configured XStream
*/
public static XStream newStaxXStream() {
XStream result = new XStream(new StaxDriver());
return result;
}
/**
* Provide a default XStream instance. With XStream 3.1, this will normally
* use the XPP XML toolkit. The returned instance will still need to be
* configured for DepAn.
*/
public static XStream newBaseXStream() {
XStream result = new XStream();
return result;
}
public static XStream newXStream(boolean readable) {
if (readable) {
return newBaseXStream();
}
return newStaxXStream();
}
/**
* Configure an XStream instance with all the specializations necessary
* for plugin support (class loading), graphs (app-level) and all the
* plugins graph elements.
*
* @param xstream instance to configure
*/
public static void configureGraphXStream(XStream xstream) {
xstream.setMode(XStream.NO_REFERENCES);
GraphElements.GRAPH_XML_PERSIST.config(xstream);
SourcePluginRegistry.configXmlPersist(xstream);
}
/**
* Configure an XStream instance with all the specializations necessary
* for references to {@code GraphModel} elements.
*
* @param xstream instance to configure
*/
public static void configureRefXStream(XStream xstream) {
// Basic configuration, class loaders, and plug-in specific types.
// For reference XStreams, we don't need the plug-ins' Node types, but we
// do need the class loaders and the plug-ins' Relation types.
configureGraphXStream(xstream);
// Add in reference converters as the favored converters.
GraphElements.REF_XML_PERSIST.config(xstream);
}
}