sdks/java/core/src/main/java/org/apache/beam/sdk/util/RowJsonDeserializer.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.apache.beam.sdk.util;

import static java.util.stream.Collectors.toList;
import static org.apache.beam.sdk.schemas.Schema.TypeName.BOOLEAN;
import static org.apache.beam.sdk.schemas.Schema.TypeName.BYTE;
import static org.apache.beam.sdk.schemas.Schema.TypeName.DECIMAL;
import static org.apache.beam.sdk.schemas.Schema.TypeName.DOUBLE;
import static org.apache.beam.sdk.schemas.Schema.TypeName.FLOAT;
import static org.apache.beam.sdk.schemas.Schema.TypeName.INT16;
import static org.apache.beam.sdk.schemas.Schema.TypeName.INT32;
import static org.apache.beam.sdk.schemas.Schema.TypeName.INT64;
import static org.apache.beam.sdk.schemas.Schema.TypeName.STRING;
import static org.apache.beam.sdk.util.RowJsonValueExtractors.booleanValueExtractor;
import static org.apache.beam.sdk.util.RowJsonValueExtractors.byteValueExtractor;
import static org.apache.beam.sdk.util.RowJsonValueExtractors.decimalValueExtractor;
import static org.apache.beam.sdk.util.RowJsonValueExtractors.doubleValueExtractor;
import static org.apache.beam.sdk.util.RowJsonValueExtractors.floatValueExtractor;
import static org.apache.beam.sdk.util.RowJsonValueExtractors.intValueExtractor;
import static org.apache.beam.sdk.util.RowJsonValueExtractors.longValueExtractor;
import static org.apache.beam.sdk.util.RowJsonValueExtractors.shortValueExtractor;
import static org.apache.beam.sdk.util.RowJsonValueExtractors.stringValueExtractor;
import static org.apache.beam.sdk.values.Row.toRow;

import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.deser.std.StdDeserializer;
import com.fasterxml.jackson.databind.node.JsonNodeType;
import com.google.auto.value.AutoValue;
import java.io.IOException;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;
import javax.annotation.Nullable;
import org.apache.beam.sdk.schemas.Schema;
import org.apache.beam.sdk.schemas.Schema.FieldType;
import org.apache.beam.sdk.schemas.Schema.TypeName;
import org.apache.beam.sdk.util.RowJsonValueExtractors.ValueExtractor;
import org.apache.beam.sdk.values.Row;
import org.apache.beam.vendor.guava.v20_0.com.google.common.collect.ImmutableMap;

/**
 * Jackson deserializer for {@link Row Rows}.
 *
 * <p>Supports converting JSON primitive types to:
 *
 * <ul>
 *   <li>{@link Schema.TypeName#BYTE}
 *   <li>{@link Schema.TypeName#INT16}
 *   <li>{@link Schema.TypeName#INT32}
 *   <li>{@link Schema.TypeName#INT64}
 *   <li>{@link Schema.TypeName#FLOAT}
 *   <li>{@link Schema.TypeName#DOUBLE}
 *   <li>{@link Schema.TypeName#BOOLEAN}
 *   <li>{@link Schema.TypeName#STRING}
 * </ul>
 */
public class RowJsonDeserializer extends StdDeserializer<Row> {

  private static final boolean SEQUENTIAL = false;

  private static final ImmutableMap<TypeName, ValueExtractor<?>> JSON_VALUE_GETTERS =
      ImmutableMap.<TypeName, ValueExtractor<?>>builder()
          .put(BYTE, byteValueExtractor())
          .put(INT16, shortValueExtractor())
          .put(INT32, intValueExtractor())
          .put(INT64, longValueExtractor())
          .put(FLOAT, floatValueExtractor())
          .put(DOUBLE, doubleValueExtractor())
          .put(BOOLEAN, booleanValueExtractor())
          .put(STRING, stringValueExtractor())
          .put(DECIMAL, decimalValueExtractor())
          .build();

  private Schema schema;

  /** Creates a deserializer for a {@link Row} {@link Schema}. */
  public static RowJsonDeserializer forSchema(Schema schema) {
    schema.getFields().forEach(RowJsonValidation::verifyFieldTypeSupported);
    return new RowJsonDeserializer(schema);
  }

  private RowJsonDeserializer(Schema schema) {
    super(Row.class);
    this.schema = schema;
  }

  @Override
  public Row deserialize(JsonParser jsonParser, DeserializationContext deserializationContext)
      throws IOException {

    // Parse and convert the root object to Row as if it's a nested field with name 'root'
    return (Row)
        extractJsonNodeValue(
            FieldValue.of("root", FieldType.row(schema), jsonParser.readValueAsTree()));
  }

  private static Object extractJsonNodeValue(FieldValue fieldValue) {
    if (!fieldValue.isJsonValuePresent()) {
      throw new UnsupportedRowJsonException(
          "Field '" + fieldValue.name() + "' is not present in the JSON object");
    }

    if (fieldValue.isJsonNull()) {
      return null;
    }

    if (fieldValue.isRowType()) {
      return jsonObjectToRow(fieldValue);
    }

    if (fieldValue.isArrayType()) {
      return jsonArrayToList(fieldValue);
    }

    return extractJsonPrimitiveValue(fieldValue);
  }

  private static Row jsonObjectToRow(FieldValue rowFieldValue) {
    if (!rowFieldValue.isJsonObject()) {
      throw new UnsupportedRowJsonException(
          "Expected JSON object for field '"
              + rowFieldValue.name()
              + "'. "
              + "Unable to convert '"
              + rowFieldValue.jsonValue().asText()
              + "'"
              + " to Beam Row, it is not a JSON object. Currently only JSON objects "
              + "can be parsed to Beam Rows");
    }

    return rowFieldValue.rowSchema().getFields().stream()
        .map(
            schemaField ->
                extractJsonNodeValue(
                    FieldValue.of(
                        schemaField.getName(),
                        schemaField.getType(),
                        rowFieldValue.jsonFieldValue(schemaField.getName()))))
        .collect(toRow(rowFieldValue.rowSchema()));
  }

  private static Object jsonArrayToList(FieldValue arrayFieldValue) {
    if (!arrayFieldValue.isJsonArray()) {
      throw new UnsupportedRowJsonException(
          "Expected JSON array for field '"
              + arrayFieldValue.name()
              + "'. "
              + "Instead got "
              + arrayFieldValue.jsonNodeType().name());
    }

    return arrayFieldValue
        .jsonArrayElements()
        .map(
            jsonArrayElement ->
                extractJsonNodeValue(
                    FieldValue.of(
                        arrayFieldValue.name() + "[]",
                        arrayFieldValue.arrayElementType(),
                        jsonArrayElement)))
        .collect(toList());
  }

  private static Object extractJsonPrimitiveValue(FieldValue fieldValue) {
    try {
      return JSON_VALUE_GETTERS.get(fieldValue.typeName()).extractValue(fieldValue.jsonValue());
    } catch (RuntimeException e) {
      throw new UnsupportedRowJsonException(
          "Unable to get value from field '"
              + fieldValue.name()
              + "'. "
              + "Schema type '"
              + fieldValue.typeName()
              + "'. "
              + "JSON node type "
              + fieldValue.jsonNodeType().name(),
          e);
    }
  }

  /** Helper class to keep track of schema field type, name, and actual json value for the field. */
  @AutoValue
  abstract static class FieldValue {
    abstract String name();

    abstract FieldType type();

    abstract @Nullable JsonNode jsonValue();

    TypeName typeName() {
      return type().getTypeName();
    }

    boolean isJsonValuePresent() {
      return jsonValue() != null;
    }

    boolean isJsonNull() {
      return jsonValue().isNull();
    }

    JsonNodeType jsonNodeType() {
      return jsonValue().getNodeType();
    }

    boolean isJsonArray() {
      return jsonValue().isArray();
    }

    Stream<JsonNode> jsonArrayElements() {
      return StreamSupport.stream(jsonValue().spliterator(), SEQUENTIAL);
    }

    boolean isArrayType() {
      return TypeName.ARRAY.equals(type().getTypeName());
    }

    FieldType arrayElementType() {
      return type().getCollectionElementType();
    }

    boolean isJsonObject() {
      return jsonValue().isObject();
    }

    JsonNode jsonFieldValue(String fieldName) {
      return jsonValue().get(fieldName);
    }

    boolean isRowType() {
      return TypeName.ROW.equals(type().getTypeName());
    }

    Schema rowSchema() {
      return type().getRowSchema();
    }

    static FieldValue of(String name, FieldType type, JsonNode jsonValue) {
      return new AutoValue_RowJsonDeserializer_FieldValue(name, type, jsonValue);
    }
  }

  /** Gets thrown when Row parsing fails for any reason. */
  public static class UnsupportedRowJsonException extends RuntimeException {

    UnsupportedRowJsonException(String message, Throwable reason) {
      super(message, reason);
    }

    UnsupportedRowJsonException(String message) {
      super(message);
    }
  }
}