OpenCSVSerde.java example

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/**
 * 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.hadoop.hive.serde2;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hive.serde.serdeConstants;
import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspector;
import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspectorFactory;
import org.apache.hadoop.hive.serde2.objectinspector.StructField;
import org.apache.hadoop.hive.serde2.objectinspector.StructObjectInspector;
import org.apache.hadoop.hive.serde2.objectinspector.primitive.PrimitiveObjectInspectorFactory;
import org.apache.hadoop.hive.serde2.objectinspector.primitive.StringObjectInspector;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.io.Writable;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.CharArrayReader;
import java.io.IOException;
import java.io.Reader;
import java.io.StringWriter;
import java.io.Writer;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Properties;

import au.com.bytecode.opencsv.CSVReader;
import au.com.bytecode.opencsv.CSVWriter;

/**
 * OpenCSVSerde use opencsv to deserialize CSV format.
 * Users can specify custom separator, quote or escape characters. And the default separator(\),
 * quote("), and escape characters(\) are the same as the opencsv library.
 *
 */
@SerDeSpec(schemaProps = {
    serdeConstants.LIST_COLUMNS,
    OpenCSVSerde.SEPARATORCHAR, OpenCSVSerde.QUOTECHAR, OpenCSVSerde.ESCAPECHAR})
public final class OpenCSVSerde extends AbstractSerDe {

  public static final Logger LOG = LoggerFactory.getLogger(OpenCSVSerde.class.getName());
  private ObjectInspector inspector;
  private String[] outputFields;
  private int numCols;
  private List<String> row;

  private char separatorChar;
  private char quoteChar;
  private char escapeChar;

  public static final String SEPARATORCHAR = "separatorChar";
  public static final String QUOTECHAR = "quoteChar";
  public static final String ESCAPECHAR = "escapeChar";

  @Override
  public void initialize(final Configuration conf, final Properties tbl) throws SerDeException {

    final List<String> columnNames = Arrays.asList(tbl.getProperty(serdeConstants.LIST_COLUMNS)
        .split(","));

    numCols = columnNames.size();

    final List<ObjectInspector> columnOIs = new ArrayList<ObjectInspector>(numCols);

    for (int i = 0; i < numCols; i++) {
      columnOIs.add(PrimitiveObjectInspectorFactory.javaStringObjectInspector);
    }

    inspector = ObjectInspectorFactory.getStandardStructObjectInspector(columnNames, columnOIs);
    outputFields = new String[numCols];
    row = new ArrayList<String>(numCols);

    for (int i = 0; i < numCols; i++) {
      row.add(null);
    }

    separatorChar = getProperty(tbl, SEPARATORCHAR, CSVWriter.DEFAULT_SEPARATOR);
    quoteChar = getProperty(tbl, QUOTECHAR, CSVWriter.DEFAULT_QUOTE_CHARACTER);
    escapeChar = getProperty(tbl, ESCAPECHAR, CSVWriter.DEFAULT_ESCAPE_CHARACTER);
  }

  private char getProperty(final Properties tbl, final String property, final char def) {
    final String val = tbl.getProperty(property);

    if (val != null) {
      return val.charAt(0);
    }

    return def;
  }

  @Override
  public Writable serialize(Object obj, ObjectInspector objInspector) throws SerDeException {
    final StructObjectInspector outputRowOI = (StructObjectInspector) objInspector;
    final List<? extends StructField> outputFieldRefs = outputRowOI.getAllStructFieldRefs();

    if (outputFieldRefs.size() != numCols) {
      throw new SerDeException("Cannot serialize the object because there are "
              + outputFieldRefs.size() + " fields but the table has " + numCols + " columns.");
    }

    // Get all data out.
    for (int c = 0; c < numCols; c++) {
      final Object field = outputRowOI.getStructFieldData(obj, outputFieldRefs.get(c));
      final ObjectInspector fieldOI = outputFieldRefs.get(c).getFieldObjectInspector();

      // The data must be of type String
      final StringObjectInspector fieldStringOI = (StringObjectInspector) fieldOI;

      // Convert the field to Java class String, because objects of String type
      // can be stored in String, Text, or some other classes.
      outputFields[c] = fieldStringOI.getPrimitiveJavaObject(field);
    }

    final StringWriter writer = new StringWriter();
    final CSVWriter csv = newWriter(writer, separatorChar, quoteChar, escapeChar);

    try {
      csv.writeNext(outputFields);
      csv.close();

      return new Text(writer.toString());
    } catch (final IOException ioe) {
      throw new SerDeException(ioe);
    }
  }

  @Override
  public Object deserialize(final Writable blob) throws SerDeException {
    Text rowText = (Text) blob;

    CSVReader csv = null;
    try {
      csv = newReader(new CharArrayReader(rowText.toString().toCharArray()), separatorChar,
              quoteChar, escapeChar);
      final String[] read = csv.readNext();

      for (int i = 0; i < numCols; i++) {
        if (read != null && i < read.length) {
          row.set(i, read[i]);
        } else {
          row.set(i, null);
        }
      }

      return row;
    } catch (final Exception e) {
      throw new SerDeException(e);
    } finally {
      if (csv != null) {
        try {
          csv.close();
        } catch (final Exception e) {
          LOG.error("fail to close csv writer ", e);
        }
      }
    }
  }

  private CSVReader newReader(final Reader reader, char separator, char quote, char escape) {
    // CSVReader will throw an exception if any of separator, quote, or escape is the same, but
    // the CSV format specifies that the escape character and quote char are the same... very weird
    if (CSVWriter.DEFAULT_ESCAPE_CHARACTER == escape) {
      return new CSVReader(reader, separator, quote);
    } else {
      return new CSVReader(reader, separator, quote, escape);
    }
  }

  private CSVWriter newWriter(final Writer writer, char separator, char quote, char escape) {
    if (CSVWriter.DEFAULT_ESCAPE_CHARACTER == escape) {
      return new CSVWriter(writer, separator, quote, "");
    } else {
      return new CSVWriter(writer, separator, quote, escape, "");
    }
  }

  @Override
  public ObjectInspector getObjectInspector() throws SerDeException {
    return inspector;
  }

  @Override
  public Class<? extends Writable> getSerializedClass() {
    return Text.class;
  }

  @Override
  public SerDeStats getSerDeStats() {
    return null;
  }
}