CsvItemReader.java

/*
 * Copyright (c) 2013 Red Hat, Inc. and/or its affiliates.
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 * Cheng Fang - Initial API and implementation
 */

package org.jberet.support.io;

import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Serializable;
import javax.batch.api.BatchProperty;
import javax.batch.api.chunk.ItemReader;
import javax.enterprise.context.Dependent;
import javax.inject.Inject;
import javax.inject.Named;

import org.jberet.support._private.SupportLogger;
import org.jberet.support._private.SupportMessages;
import org.supercsv.io.ICsvBeanReader;
import org.supercsv.io.ICsvListReader;
import org.supercsv.io.ICsvMapReader;
import org.supercsv.io.ICsvReader;

import static org.jberet.support.io.CsvProperties.BEAN_TYPE_KEY;

/**
 * An implementation of {@code javax.batch.api.chunk.ItemReader} that reads from a CSV resource into a user-defined
 * bean, java.util.List<String>, or java.util.Map<String, String>. Data files delimited with characters
 * other than comma (e.g., tab, |) are also supported by configuring {@code preference}, {@code delimiterChar},
 * or {@code quoteChar} properties in job xml.
 * This class is not designed to be thread-safe and its instance should not be shared between threads.
 *
 * @see     CsvItemReaderWriterBase
 * @see     CsvItemWriter
 * @since   1.0.0
 */
@Named
@Dependent
public class CsvItemReader extends CsvItemReaderWriterBase implements ItemReader {
    /**
     * Specifies the start position (a positive integer starting from 1) to read the data. If reading from the beginning
     * of the input CSV, there is no need to specify this property.
     */
    @Inject
    @BatchProperty
    protected int start;

    /**
     * Specify the end position in the data set (inclusive). Optional property, and defaults to {@code Integer.MAX_VALUE}.
     * If reading till the end of the input CSV, there is no need to specify this property.
     */
    @Inject
    @BatchProperty
    protected int end;

    /**
     * Indicates that the input CSV resource does not contain header row. Optional property, valid values are
     * {@code true} or {@code false}, and the default is {@code false}.
     */
    @Inject
    @BatchProperty
    protected boolean headerless;

    protected ICsvReader delegateReader;

    @Override
    public void open(final Serializable checkpoint) throws Exception {
        /**
         * The row number to start reading.  It may be different from the injected field start. During a restart,
         * we would start reading from where it ended during the last run.
         */
        if (this.end == 0) {
            this.end = Integer.MAX_VALUE;
        }
        int startRowNumber = checkpoint == null ? this.start : (Integer) checkpoint;
        if (startRowNumber < this.start || startRowNumber > this.end || startRowNumber < 0) {
            throw SupportMessages.MESSAGES.invalidStartPosition(startRowNumber, this.start, this.end);
        }
        if (headerless) {
            startRowNumber--;
            this.end--;
        }

        if (beanType == null) {
            throw SupportMessages.MESSAGES.invalidReaderWriterProperty(null, null, BEAN_TYPE_KEY);
        }
        final InputStream inputStream = getInputStream(resource, true);
        final InputStreamReader r = charset == null ? new InputStreamReader(inputStream) :
                new InputStreamReader(inputStream, charset);
        if (java.util.List.class.isAssignableFrom(beanType)) {
            delegateReader = new FastForwardCsvListReader(r, getCsvPreference(), startRowNumber);
        } else if (java.util.Map.class.isAssignableFrom(beanType)) {
            delegateReader = new FastForwardCsvMapReader(r, getCsvPreference(), startRowNumber);
        } else {
            delegateReader = new FastForwardCsvBeanReader(r, getCsvPreference(), startRowNumber);
        }
        SupportLogger.LOGGER.openingResource(resource, this.getClass());

        if (!headerless) {
            final String[] header;
            try {
                header = delegateReader.getHeader(true);    //first line check true
            } catch (final IOException e) {
                throw SupportMessages.MESSAGES.failToReadCsvHeader(e, resource);
            }
            if (this.nameMapping == null) {
                this.nameMapping = header;
            }
        }
        this.cellProcessorInstances = getCellProcessors();
    }

    @Override
    public void close() throws Exception {
        if (delegateReader != null) {
            SupportLogger.LOGGER.closingResource(resource, this.getClass());
            delegateReader.close();
            delegateReader = null;
        }
    }

    @Override
    public Object readItem() throws Exception {
        if (delegateReader.getRowNumber() > this.end) {
            return null;
        }
        final Object result;
        if (delegateReader instanceof org.supercsv.io.ICsvBeanReader) {
            if (cellProcessorInstances.length == 0) {
                result = ((ICsvBeanReader) delegateReader).read(beanType, getNameMapping());
            } else {
                result = ((ICsvBeanReader) delegateReader).read(beanType, getNameMapping(), cellProcessorInstances);
            }
            if (!skipBeanValidation) {
                ItemReaderWriterBase.validate(result);
            }
        } else if (delegateReader instanceof ICsvListReader) {
            if (cellProcessorInstances.length == 0) {
                result = ((ICsvListReader) delegateReader).read();
            } else {
                result = ((ICsvListReader) delegateReader).read(cellProcessorInstances);
            }
        } else {
            if (cellProcessorInstances.length == 0) {
                result = ((ICsvMapReader) delegateReader).read(getNameMapping());
            } else {
                result = ((ICsvMapReader) delegateReader).read(getNameMapping(), cellProcessorInstances);
            }
        }
        return result;
    }

    @Override
    public Integer checkpointInfo() throws Exception {
        return delegateReader.getRowNumber();
    }
}