Converter.java
/*
* Copyright (c) 2008, Harald Kuhr
* All rights reserved.
*
* 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 the copyright holder 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 HOLDER 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 com.twelvemonkeys.util.convert;
import com.twelvemonkeys.util.Time;
import java.util.Date;
import java.util.Hashtable;
import java.util.Map;
/**
* The converter (singleton). Converts strings to objects and back.
* This is the entry point to the converter framework.
* <p>
* By default, converters for {@link com.twelvemonkeys.util.Time}, {@link Date}
* and {@link Object}
* (the {@link DefaultConverter}) are registered by this class' static
* initializer. You might remove them using the
* {@code unregisterConverter} method.
* </p>
*
* @see #registerConverter(Class, PropertyConverter)
* @see #unregisterConverter(Class)
*
* @author <a href="mailto:harald.kuhr@gmail.com">Harald Kuhr</a>
* @author last modified by $Author: haku $
* @version $Id: //depot/branches/personal/haraldk/twelvemonkeys/release-2/twelvemonkeys-core/src/main/java/com/twelvemonkeys/util/convert/Converter.java#1 $
*/
// TODO: Get rid of singleton stuff
// Can probably be a pure static class, but is that a good idea?
// Maybe have BeanUtil act as a "proxy", and hide this class all together?
// TODO: ServiceRegistry for registering 3rd party converters
// TODO: URI scheme, for implicit typing? Is that a good idea?
// TODO: Array converters?
public abstract class Converter implements PropertyConverter {
/** Our singleton instance */
protected static final Converter sInstance = new ConverterImpl(); // Thread safe & EASY
/** The converters Map */
protected final Map<Class, PropertyConverter> converters = new Hashtable<Class, PropertyConverter>();
// Register our predefined converters
static {
PropertyConverter defaultConverter = new DefaultConverter();
registerConverter(Object.class, defaultConverter);
registerConverter(Boolean.TYPE, defaultConverter);
PropertyConverter numberConverter = new NumberConverter();
registerConverter(Number.class, numberConverter);
registerConverter(Byte.TYPE, numberConverter);
registerConverter(Double.TYPE, numberConverter);
registerConverter(Float.TYPE, numberConverter);
registerConverter(Integer.TYPE, numberConverter);
registerConverter(Long.TYPE, numberConverter);
registerConverter(Short.TYPE, numberConverter);
registerConverter(Date.class, new DateConverter());
registerConverter(Time.class, new TimeConverter());
}
/**
* Creates a Converter.
*/
protected Converter() {
}
/**
* Gets the Converter instance.
*
* @return the converter instance
*/
public static Converter getInstance() {
return sInstance;
}
/**
* Registers a converter for a given type.
* This converter will also be used for all subclasses, unless a more
* specific version is registered.
* <p>
* By default, converters for {@link com.twelvemonkeys.util.Time}, {@link Date}
* and {@link Object}
* (the {@link DefaultConverter}) are registered by this class' static
* initializer. You might remove them using the
* {@code unregisterConverter} method.
* </p>
*
* @param pType the (super) type to register a converter for
* @param pConverter the converter
*
* @see #unregisterConverter(Class)
*/
public static void registerConverter(final Class<?> pType, final PropertyConverter pConverter) {
getInstance().converters.put(pType, pConverter);
}
/**
* Un-registers a converter for a given type. That is, making it unavailable
* for the converter framework, and making it (potentially) available for
* garbage collection.
*
* @param pType the (super) type to remove converter for
*
* @see #registerConverter(Class,PropertyConverter)
*/
@SuppressWarnings("UnusedDeclaration")
public static void unregisterConverter(final Class<?> pType) {
getInstance().converters.remove(pType);
}
/**
* Converts the string to an object of the given type.
*
* @param pString the string to convert
* @param pType the type to convert to
*
* @return the object created from the given string.
*
* @throws ConversionException if the string cannot be converted for any
* reason.
*/
public Object toObject(final String pString, final Class pType) throws ConversionException {
return toObject(pString, pType, null);
}
/**
* Converts the string to an object of the given type, parsing after the
* given format.
*
* @param pString the string to convert
* @param pType the type to convert to
* @param pFormat the (optional) conversion format
*
* @return the object created from the given string.
*
* @throws ConversionException if the string cannot be converted for any
* reason.
*/
public abstract Object toObject(String pString, Class pType, String pFormat)
throws ConversionException;
/**
* Converts the object to a string, using {@code object.toString()}
*
* @param pObject the object to convert.
*
* @return the string representation of the object, on the correct format.
*
* @throws ConversionException if the object cannot be converted to a
* string for any reason.
*/
public String toString(final Object pObject) throws ConversionException {
return toString(pObject, null);
}
/**
* Converts the object to a string, using {@code object.toString()}
*
* @param pObject the object to convert.
* @param pFormat the (optional) conversion format
*
* @return the string representation of the object, on the correct format.
*
* @throws ConversionException if the object cannot be converted to a
* string for any reason.
*/
public abstract String toString(Object pObject, String pFormat)
throws ConversionException;
}