DocumentToMetadataProcessor.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
 *
 *   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.streams.elasticsearch.processor;

import org.apache.streams.core.StreamsDatum;
import org.apache.streams.core.StreamsProcessor;
import org.apache.streams.elasticsearch.ElasticsearchMetadataUtil;
import org.apache.streams.jackson.StreamsJacksonMapper;

import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.node.ObjectNode;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;

/**
 * Moves a json representation of metadata out of the document to the metadata field.
 *
 * <p/>
 * This is useful if you have a list of document metadata references in the document field,
 * for example loaded from a file, and need them in the metadata field.
 */
public class DocumentToMetadataProcessor implements StreamsProcessor, Serializable {

  private static final String STREAMS_ID = "DatumFromMetadataProcessor";

  private ObjectMapper mapper;

  private static final Logger LOGGER = LoggerFactory.getLogger(DocumentToMetadataProcessor.class);

  public DocumentToMetadataProcessor() {
  }

  @Override
  public String getId() {
    return STREAMS_ID;
  }

  @Override
  public List<StreamsDatum> process(StreamsDatum entry) {
    List<StreamsDatum> result = new ArrayList<>();

    Object object = entry.getDocument();
    ObjectNode metadataObjectNode;
    try {
      String docAsJson = (object instanceof String) ? object.toString() : mapper.writeValueAsString(object);
      metadataObjectNode = mapper.readValue(docAsJson, ObjectNode.class);
    } catch (Throwable ex) {
      LOGGER.warn("Exception: %s", ex.getMessage());
      return result;
    }

    Map<String, Object> metadata = ElasticsearchMetadataUtil.asMap(metadataObjectNode);

    if ( metadata == null ) {
      return result;
    }

    entry.setMetadata(metadata);

    result.add(entry);

    return result;
  }

  @Override
  public void prepare(Object configurationObject) {
    mapper = StreamsJacksonMapper.getInstance();
  }

  @Override
  public void cleanUp() {
    mapper = null;
  }

}