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/*
 * Copyright 2011-2018 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.data.redis.serializer;

import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;

import org.springframework.beans.BeansException;
import org.springframework.beans.TypeConverter;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.BeanFactoryAware;
import org.springframework.beans.factory.config.ConfigurableBeanFactory;
import org.springframework.core.convert.ConversionService;
import org.springframework.core.convert.support.DefaultConversionService;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;

/**
 * Generic String to byte[] (and back) serializer. Relies on the Spring {@link ConversionService} to transform objects
 * into String and vice versa. The Strings are convert into bytes and vice-versa using the specified charset (by default
 * UTF-8). Note: The conversion service initialization happens automatically if the class is defined as a Spring
 * bean. Note: Does not handle nulls in any special way delegating everything to the container.
 *
 * @author Costin Leau
 * @author Christoph Strobl
 * @author Mark Paluch
 */
public class GenericToStringSerializer implements RedisSerializer, BeanFactoryAware {

	private final Class type;
	private final Charset charset;

	private Converter converter = new Converter(new DefaultConversionService());

	public GenericToStringSerializer(Class type) {
		this(type, StandardCharsets.UTF_8);
	}

	public GenericToStringSerializer(Class type, Charset charset) {

		Assert.notNull(type, "Type must not be null!");

		this.type = type;
		this.charset = charset;
	}

	public void setConversionService(ConversionService conversionService) {

		Assert.notNull(conversionService, "non null conversion service required");
		converter = new Converter(conversionService);
	}

	public void setTypeConverter(TypeConverter typeConverter) {

		Assert.notNull(typeConverter, "non null type converter required");
		converter = new Converter(typeConverter);
	}

	@Override
	public T deserialize(@Nullable byte[] bytes) {

		if (bytes == null) {
			return null;
		}

		String string = new String(bytes, charset);
		return converter.convert(string, type);
	}

	@Override
	public byte[] serialize(@Nullable T object) {
		if (object == null) {
			return null;
		}
		String string = converter.convert(object, String.class);
		return string.getBytes(charset);
	}

	public void setBeanFactory(BeanFactory beanFactory) throws BeansException {

		// TODO: This code can never happen...
		if (converter == null && beanFactory instanceof ConfigurableBeanFactory) {
			ConfigurableBeanFactory cFB = (ConfigurableBeanFactory) beanFactory;
			ConversionService conversionService = cFB.getConversionService();

			converter = (conversionService != null ? new Converter(conversionService)
					: new Converter(cFB.getTypeConverter()));
		}
	}

	private class Converter {
		private final ConversionService conversionService;
		private final TypeConverter typeConverter;

		public Converter(ConversionService conversionService) {
			this.conversionService = conversionService;
			this.typeConverter = null;
		}

		public Converter(TypeConverter typeConverter) {
			this.conversionService = null;
			this.typeConverter = typeConverter;
		}

		 E convert(Object value, Class targetType) {
			if (conversionService != null) {
				return conversionService.convert(value, targetType);
			}
			return typeConverter.convertIfNecessary(value, targetType);
		}
	}
}