/*
 * Copyright 2002-2013 the original author or authors.
 *
 * 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 org.springframework.core.convert.support;

import java.io.StringWriter;
import java.util.Collections;
import java.util.Set;

import org.springframework.core.convert.TypeDescriptor;
import org.springframework.core.convert.converter.ConditionalGenericConverter;
import org.springframework.util.ClassUtils;

/**
 * Simply calls {@link Object#toString()} to convert any supported Object to a String.
 * Supports CharSequence, StringWriter, and any class with a String constructor or
 * {@code valueOf(String)} method.
 *
 * <p>Used by the default ConversionService as a fallback if there are no other explicit
 * to-String converters registered.
 *
 * @author Keith Donald
 * @author Juergen Hoeller
 * @since 3.0
 */
final class FallbackObjectToStringConverter implements ConditionalGenericConverter {

	@Override
	public Set<ConvertiblePair> getConvertibleTypes() {
		return Collections.singleton(new ConvertiblePair(Object.class, String.class));
	}

	@Override
	public boolean matches(TypeDescriptor sourceType, TypeDescriptor targetType) {
		Class<?> sourceClass = sourceType.getObjectType();
		if (String.class.equals(sourceClass)) {
			return false;
		}
		return (CharSequence.class.isAssignableFrom(sourceClass) ||
				StringWriter.class.isAssignableFrom(sourceClass) ||
				ObjectToObjectConverter.getOfMethod(sourceClass, String.class) != null ||
				ClassUtils.getConstructorIfAvailable(sourceClass, String.class) != null);
	}

	@Override
	public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
		return (source != null ? source.toString() : null);
	}

}
