com.ibm.watson.catalyst.objectio.writers.CSVOutputWriter.java Source code

Introduction

Here is the source code for com.ibm.watson.catalyst.objectio.writers.CSVOutputWriter.java

Source

/*******************************************************************************
 * Copyright 2015 IBM Corporation
 *
 * 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
 *
 *     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 com.ibm.watson.catalyst.objectio.writers;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.util.Collection;
import java.util.List;
import java.util.Optional;

import org.apache.commons.csv.CSVFormat;
import org.apache.commons.csv.CSVPrinter;

/**
 * Writes a collection of writable objects in CSV form
 * 
 * @author Will Beason
 * @version 0.1.0
 * @param <V> the type of object written to a CSV
 * @since 0.1.0
 *
 */
public class CSVOutputWriter<V> implements IOutputWriter {

    private final String _encoding;

    private final File _outFile;

    /**
     * Instantiates a new CSVOutputWriter and defaults to UTF-8 encoding.
     * 
     * @param aOutFile the file to write to
     */
    public CSVOutputWriter(final File aOutFile) {
        this(aOutFile, "UTF-8");
    }

    /**
     * Instantiates a new CSVOutputWriter with specified encoding.
     * 
     * @param aOutFile the file to write to
     * @param aEncoding the encoding to use
     */
    public CSVOutputWriter(final File aOutFile, final String aEncoding) {
        this(aOutFile, aEncoding, null);
    }

    /**
     * @param aOutFile the file to write to
     * @param aEncoding the encoding to use
     * @param aHeader the header to include
     */
    public CSVOutputWriter(final File aOutFile, final String aEncoding, final List<String> aHeader) {
        _outFile = aOutFile;
        _encoding = aEncoding;
        _header = Optional.ofNullable(aHeader);
    }

    @Override
    public void write(final Collection<? extends IWritable> writables) {
        try (OutputStreamWriter writer = new OutputStreamWriter(new FileOutputStream(_outFile), _encoding)) {
            try (CSVPrinter printer = new CSVPrinter(writer, FORMAT);) {
                if (_header.isPresent())
                    printer.printRecord(_header.get());
                printer.printRecords(writables);
            } catch (final IOException e) {
                throw new RuntimeException("IOError writing to " + _outFile, e);
            }
        } catch (final IOException e) {
            throw new RuntimeException("IOError opening " + _outFile + " for writing.");
        }
    }

    private static final CSVFormat FORMAT = CSVFormat.RFC4180.withDelimiter('\t');
    private final Optional<List<String>> _header;

}