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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.lang.Nullable;
import org.springframework.util.Assert;

import com.fasterxml.jackson.databind.JavaType;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.ser.SerializerFactory;
import com.fasterxml.jackson.databind.type.TypeFactory;

/**
 * {@link RedisSerializer} that can read and write JSON using
 * Jackson's and
 * Jackson Databind {@link ObjectMapper}.
 * 
 * This converter can be used to bind to typed beans, or untyped {@link java.util.HashMap HashMap} instances.
 * Note:Null objects are serialized as empty arrays and vice versa.
 *
 * @author Thomas Darimont
 * @since 1.2
 */
public class Jackson2JsonRedisSerializer implements RedisSerializer {

	public static final Charset DEFAULT_CHARSET = StandardCharsets.UTF_8;

	private final JavaType javaType;

	private ObjectMapper objectMapper = new ObjectMapper();

	/**
	 * Creates a new {@link Jackson2JsonRedisSerializer} for the given target {@link Class}.
	 *
	 * @param type
	 */
	public Jackson2JsonRedisSerializer(Class type) {
		this.javaType = getJavaType(type);
	}

	/**
	 * Creates a new {@link Jackson2JsonRedisSerializer} for the given target {@link JavaType}.
	 *
	 * @param javaType
	 */
	public Jackson2JsonRedisSerializer(JavaType javaType) {
		this.javaType = javaType;
	}

	@SuppressWarnings("unchecked")
	public T deserialize(@Nullable byte[] bytes) throws SerializationException {

		if (SerializationUtils.isEmpty(bytes)) {
			return null;
		}
		try {
			return (T) this.objectMapper.readValue(bytes, 0, bytes.length, javaType);
		} catch (Exception ex) {
			throw new SerializationException("Could not read JSON: " + ex.getMessage(), ex);
		}
	}

	@Override
	public byte[] serialize(@Nullable Object t) throws SerializationException {

		if (t == null) {
			return SerializationUtils.EMPTY_ARRAY;
		}
		try {
			return this.objectMapper.writeValueAsBytes(t);
		} catch (Exception ex) {
			throw new SerializationException("Could not write JSON: " + ex.getMessage(), ex);
		}
	}

	/**
	 * Sets the {@code ObjectMapper} for this view. If not set, a default {@link ObjectMapper#ObjectMapper() ObjectMapper}
	 * is used.
	 * 

	 * Setting a custom-configured {@code ObjectMapper} is one way to take further control of the JSON serialization
	 * process. For example, an extended {@link SerializerFactory} can be configured that provides custom serializers for
	 * specific types. The other option for refining the serialization process is to use Jackson's provided annotations on
	 * the types to be serialized, in which case a custom-configured ObjectMapper is unnecessary.
	 */
	public void setObjectMapper(ObjectMapper objectMapper) {

		Assert.notNull(objectMapper, "'objectMapper' must not be null");
		this.objectMapper = objectMapper;
	}

	/**
	 * Returns the Jackson {@link JavaType} for the specific class.
	 * 

	 * Default implementation returns {@link TypeFactory#constructType(java.lang.reflect.Type)}, but this can be
	 * overridden in subclasses, to allow for custom generic collection handling. For instance:
	 *
	 * 
	 * protected JavaType getJavaType(Class<?> clazz) {
	 * 	if (List.class.isAssignableFrom(clazz)) {
	 * 		return TypeFactory.defaultInstance().constructCollectionType(ArrayList.class, MyBean.class);
	 * 	} else {
	 * 		return super.getJavaType(clazz);
	 * 	}
	 * }
	 * 
	 *
	 * @param clazz the class to return the java type for
	 * @return the java type
	 */
	protected JavaType getJavaType(Class clazz) {
		return TypeFactory.defaultInstance().constructType(clazz);
	}
}