com.datastax.driver.extras.codecs.json.JacksonJsonCodec Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of cassandra-driver-extras Show documentation
Extended functionality for the Java driver.
The newest version!
/*
 * Copyright DataStax, Inc.
 *
 * 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 com.datastax.driver.extras.codecs.json;

import com.datastax.driver.core.DataType;
import com.datastax.driver.core.ParseUtils;
import com.datastax.driver.core.ProtocolVersion;
import com.datastax.driver.core.TypeCodec;
import com.datastax.driver.core.exceptions.InvalidTypeException;
import com.datastax.driver.core.utils.Bytes;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JavaType;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.type.TypeFactory;
import com.google.common.reflect.TypeToken;
import java.io.IOException;
import java.nio.ByteBuffer;

/**
 * A JSON codec that uses the Jackson library to
 * perform serialization and deserialization of JSON objects.
 *
 * This codec maps a single Java object to a single JSON structure at a time; mapping of arrays
 * or collections to root-level JSON arrays is not supported, but such a codec can be easily crafted
 * after this one.
 *
 * 
Note that this codec requires the presence of Jackson library at runtime. If you use Maven,
 * this can be done by declaring the following dependency in your project:
 *
 * 

 *
 * 
{@code
 * 
 *   com.fasterxml.jackson.core
 *   jackson-databind
 *   2.6.3
 * 
 * }
 */
public class JacksonJsonCodec extends TypeCodec {

  private final ObjectMapper objectMapper;

  /**
   * Creates a new instance for the provided {@code javaClass}, using a default, newly-allocated
   * {@link ObjectMapper}.
   *
   * @param javaClass the Java class this codec maps to.
   */
  public JacksonJsonCodec(Class javaClass) {
    this(javaClass, new ObjectMapper());
  }

  /**
   * Creates a new instance for the provided {@code javaType}, using a default, newly-allocated
   * {@link ObjectMapper}.
   *
   * @param javaType the Java type this codec maps to.
   */
  public JacksonJsonCodec(TypeToken javaType) {
    this(javaType, new ObjectMapper());
  }

  /**
   * Creates a new instance for the provided {@code javaClass}, and using the provided {@link
   * ObjectMapper}.
   *
   * @param javaClass the Java class this codec maps to.
   */
  public JacksonJsonCodec(Class javaClass, ObjectMapper objectMapper) {
    this(TypeToken.of(javaClass), objectMapper);
  }

  /**
   * Creates a new instance for the provided {@code javaType}, and using the provided {@link
   * ObjectMapper}.
   *
   * @param javaType the Java type this codec maps to.
   */
  public JacksonJsonCodec(TypeToken javaType, ObjectMapper objectMapper) {
    super(DataType.varchar(), javaType);
    this.objectMapper = objectMapper;
  }

  @Override
  public ByteBuffer serialize(T value, ProtocolVersion protocolVersion)
      throws InvalidTypeException {
    if (value == null) return null;
    try {
      return ByteBuffer.wrap(objectMapper.writeValueAsBytes(value));
    } catch (JsonProcessingException e) {
      throw new InvalidTypeException(e.getMessage(), e);
    }
  }

  @Override
  @SuppressWarnings("unchecked")
  public T deserialize(ByteBuffer bytes, ProtocolVersion protocolVersion)
      throws InvalidTypeException {
    if (bytes == null) return null;
    try {
      return (T) objectMapper.readValue(Bytes.getArray(bytes), toJacksonJavaType());
    } catch (IOException e) {
      throw new InvalidTypeException(e.getMessage(), e);
    }
  }

  @Override
  public String format(T value) throws InvalidTypeException {
    if (value == null) return "NULL";
    String json;
    try {
      json = objectMapper.writeValueAsString(value);
    } catch (IOException e) {
      throw new InvalidTypeException(e.getMessage(), e);
    }
    return ParseUtils.quote(json);
  }

  @Override
  @SuppressWarnings("unchecked")
  public T parse(String value) throws InvalidTypeException {
    if (value == null || value.isEmpty() || value.equalsIgnoreCase("NULL")) return null;
    if (!ParseUtils.isQuoted(value))
      throw new InvalidTypeException("JSON strings must be enclosed by single quotes");
    String json = ParseUtils.unquote(value);
    try {
      return (T) objectMapper.readValue(json, toJacksonJavaType());
    } catch (IOException e) {
      throw new InvalidTypeException(e.getMessage(), e);
    }
  }

  /**
   * This method acts as a bridge between Guava's {@link com.google.common.reflect.TypeToken
   * TypeToken} API, which is used by the driver, and Jackson's {@link JavaType} API.
   *
   * @return A {@link JavaType} instance corresponding to the codec's {@link #getJavaType() Java
   *     type}.
   */
  protected JavaType toJacksonJavaType() {
    return TypeFactory.defaultInstance().constructType(getJavaType().getType());
  }
}