/* * Copyright 2019 Google LLC * * 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 * * https://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.google.cloud.bqetl.json; import com.fasterxml.jackson.core.JsonFactory; import com.fasterxml.jackson.core.JsonParser; import com.fasterxml.jackson.core.JsonToken; import com.fasterxml.jackson.databind.JsonNode; import com.fasterxml.jackson.databind.ObjectMapper; import com.google.cloud.bqetl.mbdata.MusicBrainzDataObject; import org.slf4j.Logger; import org.slf4j.LoggerFactory; /** * Uses builtin jackson parser to parse a line of JSON and turn it into an MusicBrainzDataObject. */ public class JSONReader { private static final Logger logger = LoggerFactory.getLogger(JSONReader.class); /** * This method attempts to transform the json node into an object with a known type. * * @return an Object with the apparent type from JSON (number types are given their wide equivalent (Long for * ints, Double for float) */ private static Object nodeValueToObject(JsonNode node) { //No child objects or arrays in this flat data just text/number switch (node.getNodeType()) { case NUMBER: if (node.isFloat() || node.isDouble()) { return new Double(node.doubleValue()); } else { //For simplicity let all integers be Long. return new Long(node.asLong()); } case STRING: return node.asText(); case BOOLEAN: return node.asBoolean(); case NULL: return null; default: logger.warn("Unknown node type:" + node.getNodeType()); return null; } } /** * Reads an MusicBrainzDataObject from a json string. * * @param objectName - the namespace for the object * @param json the json string * @return */ public static MusicBrainzDataObject readObject(String objectName, String json) { MusicBrainzDataObject datum = new MusicBrainzDataObject(objectName); JsonFactory factory = new JsonFactory(); try { JsonParser parser = factory.createParser(json); parser.setCodec(new ObjectMapper()); while (!parser.isClosed()) { JsonToken token = parser.nextToken(); if (token != null && token.equals(JsonToken.START_OBJECT)) { JsonNode jsonTree = parser.readValueAsTree(); jsonTree.fields().forEachRemaining(entry -> { if (entry.getValue() != null) { Object value = nodeValueToObject(entry.getValue()); if (value == null) { // NOOP - unknown node type } else { datum.addColumnValue(entry.getKey(), nodeValueToObject(entry.getValue())); } } else { logger.warn("null value for entry : " + entry.getKey()); } }); } } } catch (Exception e) { logger.error("parse exception", e); } return datum; } }