Github user uce commented on a diff in the pull request: https://github.com/apache/flink/pull/2069#discussion_r66606127 --- Diff: flink-streaming-connectors/flink-connector-kafka-base/src/main/java/org/apache/flink/streaming/util/serialization/JsonRowDeserializationSchema.java --- @@ -0,0 +1,116 @@ +/* + * 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.flink.streaming.util.serialization; + +import com.fasterxml.jackson.databind.JsonNode; +import com.fasterxml.jackson.databind.ObjectMapper; +import org.apache.flink.api.common.typeinfo.TypeInformation; +import org.apache.flink.api.java.typeutils.TypeExtractor; +import org.apache.flink.api.table.Row; +import org.apache.flink.api.table.typeutils.RowTypeInfo; +import org.apache.flink.util.Preconditions; + +import java.io.IOException; + +/** + * Deserialization schema from JSON to {@link Row}. + * + * <p>Deserializes the <code>byte[]</code> messages as a JSON object and reads + * the specified fields. + * + * <p>Failure during deserialization are forwarded as wrapped IOExceptions. + */ +public class JsonRowDeserializationSchema implements DeserializationSchema<Row> { + + /** Field names to parse. Indices match fieldTypes indices. */ + private final String[] fieldNames; + + /** Types to parse fields as. Indices match fieldNames indices. */ + private final TypeInformation<?>[] fieldTypes; + + /** Object mapper for parsing the JSON. */ + private final ObjectMapper objectMapper = new ObjectMapper(); + + /** + * Creates a JSON deserializtion schema for the given fields and type classes. + * + * @param fieldNames Names of JSON fields to parse. + * @param fieldTypes Type classes to parse JSON fields as. + */ + public JsonRowDeserializationSchema(String[] fieldNames, Class<?>[] fieldTypes) { + this.fieldNames = Preconditions.checkNotNull(fieldNames, "Field names"); + + this.fieldTypes = new TypeInformation[fieldTypes.length]; + for (int i = 0; i < fieldTypes.length; i++) { + this.fieldTypes[i] = TypeExtractor.getForClass(fieldTypes[i]); + } + + Preconditions.checkArgument(fieldNames.length == fieldTypes.length, + "Number of provided field names and types does not match."); + } + + /** + * Creates a JSON deserializtion schema for the given fields and types. + * + * @param fieldNames Names of JSON fields to parse. + * @param fieldTypes Types to parse JSON fields as. + */ + public JsonRowDeserializationSchema(String[] fieldNames, TypeInformation<?>[] fieldTypes) { + this.fieldNames = Preconditions.checkNotNull(fieldNames, "Field names"); + this.fieldTypes = Preconditions.checkNotNull(fieldTypes, "Field types"); + + Preconditions.checkArgument(fieldNames.length == fieldTypes.length, + "Number of provided field names and types does not match."); + } + + @Override + public Row deserialize(byte[] message) throws IOException { + try { + JsonNode root = objectMapper.readTree(message); + + Row row = new Row(fieldNames.length); + for (int i = 0; i < fieldNames.length; i++) { + JsonNode node = root.get(fieldNames[i]); + + if (node == null) { --- End diff -- Good idea. Would make sense to default to that behaviour actually. Otherwise a malformatted JSON will kill the job.
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