de.intarsys.tools.converter.DoubleDispatchConverter Maven / Gradle / Ivy
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/*
* Copyright (c) 2012, intarsys consulting GmbH
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* - Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* - Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* - Neither the name of intarsys nor the names of its contributors may be used
* to endorse or promote products derived from this software without specific
* prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
package de.intarsys.tools.converter;
import java.util.HashMap;
import java.util.Map;
/**
* Double dispatch converter.
*
* This is the result of the first stage in the conversion process. A
* {@link IConverter} that bundles all {@link IConverter} instances that can
* create a dedicated target type. Amongst the sub-converters the one is
* selected that most closely supports the source object type.
*/
public class DoubleDispatchConverter implements IConverter {
final private Map converters = new HashMap();
final private Class targetType;
public DoubleDispatchConverter(Class targetType) {
super();
this.targetType = targetType;
}
public Object convert(Object source) throws ConversionException {
IConverter converter = lookupConverter(source);
if (converter == null) {
if (targetType == Canonical.class) {
// break recursion
throw new ConversionException("can't convert "
+ source.getClass().getName() + " to "
+ getTargetType());
}
Object canonical = ConverterRegistry.get().convert(source,
Canonical.class);
if (canonical == source) {
// break recursion
throw new ConversionException("can't convert "
+ source.getClass().getName() + " to "
+ getTargetType());
}
return ConverterRegistry.get().convert(canonical, getTargetType());
}
return converter.convert(source);
}
public Class getSourceType() {
return Object.class;
}
public Class getTargetType() {
return targetType;
}
private IConverter lookupConverter(Class clazz) {
IConverter result = converters.get(clazz);
if (result != null) {
return result;
}
java.lang.Class[] interfaces = clazz.getInterfaces();
for (int i = 0; i < interfaces.length; i++) {
result = lookupConverter(interfaces[i]);
if (result != null) {
return result;
}
}
java.lang.Class superClass = clazz.getSuperclass();
if (superClass != null) {
result = lookupConverter(superClass);
if (result != null) {
return result;
}
}
return null;
}
protected IConverter lookupConverter(Object source) {
Class clazz = (source == null) ? Undefined.class : source.getClass();
IConverter converter = lookupConverter(clazz);
return converter;
}
public void registerConverter(IConverter converter) {
converters.put(converter.getSourceType(), converter);
}
public void unregisterConverter(IConverter converter) {
converters.remove(converter.getSourceType());
}
}