external/sql/storm-sql-kafka/src/jvm/org/apache/storm/sql/kafka/JsonSerializer.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
 * <p>
 * http://www.apache.org/licenses/LICENSE-2.0
 * <p>
 * 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.storm.sql.kafka;

import com.fasterxml.jackson.core.JsonFactory;
import com.fasterxml.jackson.core.JsonGenerator;
import com.google.common.base.Preconditions;
import org.apache.commons.io.Charsets;
import org.apache.commons.lang.CharSet;
import org.apache.storm.sql.runtime.IOutputSerializer;

import java.io.IOException;
import java.io.StringWriter;
import java.nio.ByteBuffer;
import java.nio.charset.Charset;
import java.util.List;

class JsonSerializer implements IOutputSerializer {
  private final List<String> fieldNames;
  private transient final JsonFactory jsonFactory;

  JsonSerializer(List<String> fieldNames) {
    this.fieldNames = fieldNames;
    jsonFactory = new JsonFactory();
  }

  @Override
  public ByteBuffer write(List<Object> data, ByteBuffer buffer) {
    Preconditions.checkArgument(data != null && data.size() == fieldNames.size(), "Invalid schema");
    StringWriter sw = new StringWriter();
    try (JsonGenerator jg = jsonFactory.createGenerator(sw)) {
      jg.writeStartObject();
      for (int i = 0; i < fieldNames.size(); ++i) {
        jg.writeFieldName(fieldNames.get(i));
        jg.writeObject(data.get(i));
      }
      jg.writeEndObject();
    } catch (IOException e) {
      throw new RuntimeException(e);
    }
    return ByteBuffer.wrap(sw.toString().getBytes(Charsets.UTF_8));
  }
}