org.apache.poi.examples.ss.ToCSV Maven / Gradle / Ivy
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package org.apache.poi.examples.ss;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FilenameFilter;
import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.util.ArrayList;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.CellType;
import org.apache.poi.ss.usermodel.DataFormatter;
import org.apache.poi.ss.usermodel.FormulaEvaluator;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.ss.usermodel.Sheet;
import org.apache.poi.ss.usermodel.Workbook;
import org.apache.poi.ss.usermodel.WorkbookFactory;
/**
* Demonstrates one way to convert an Excel spreadsheet into a CSV
* file. This class makes the following assumptions;
*
* - 1. Where the Excel workbook contains more than one worksheet, then a single
* CSV file will contain the data from all of the worksheets.
* - 2. The data matrix contained in the CSV file will be square. This means that
* the number of fields in each record of the CSV file will match the number
* of cells in the longest row found in the Excel workbook. Any short records
* will be 'padded' with empty fields - an empty field is represented in
* the CSV file in this way - ,,.
* - 3. Empty fields will represent missing cells.
* - 4. A record consisting of empty fields will be used to represent an empty row
* in the Excel workbook.
*
* Therefore, if the worksheet looked like this;
*
*
* ___________________________________________
* | | | | | |
* | A | B | C | D | E |
* ___|_______|_______|_______|_______|_______|
* | | | | | |
* 1 | 1 | 2 | 3 | 4 | 5 |
* ___|_______|_______|_______|_______|_______|
* | | | | | |
* 2 | | | | | |
* ___|_______|_______|_______|_______|_______|
* | | | | | |
* 3 | | A | | B | |
* ___|_______|_______|_______|_______|_______|
* | | | | | |
* 4 | | | | | Z |
* ___|_______|_______|_______|_______|_______|
* | | | | | |
* 5 | 1,400 | | 250 | | |
* ___|_______|_______|_______|_______|_______|
*
*
*
* Then, the resulting CSV file will contain the following lines (records);
*
* 1,2,3,4,5
* ,,,,
* ,A,,B,
* ,,,,Z
* "1,400",,250,,
*
* Typically, the comma is used to separate each of the fields that, together,
* constitute a single record or line within the CSV file. This is not however
* a hard and fast rule and so this class allows the user to determine which
* character is used as the field separator and assumes the comma if none other
* is specified.
*
* If a field contains the separator then it will be escaped. If the file should
* obey Excel's CSV formatting rules, then the field will be surrounded with
* speech marks whilst if it should obey UNIX conventions, each occurrence of
* the separator will be preceded by the backslash character.
*
* If a field contains an end of line (EOL) character then it too will be
* escaped. If the file should obey Excel's CSV formatting rules then the field
* will again be surrounded by speech marks. On the other hand, if the file
* should follow UNIX conventions then a single backslash will precede the
* EOL character. There is no single applicable standard for UNIX and some
* applications replace the CR with \r and the LF with \n but this class will
* not do so.
*
* If the field contains double quotes then that character will be escaped. It
* seems as though UNIX does not define a standard for this whilst Excel does.
* Should the CSV file have to obey Excel's formatting rules then the speech
* mark character will be escaped with a second set of speech marks. Finally, an
* enclosing set of speech marks will also surround the entire field. Thus, if
* the following line of text appeared in a cell - "Hello" he said - it would
* look like this when converted into a field within a CSV file - """Hello"" he
* said".
*
* Finally, it is worth noting that talk of CSV 'standards' is really slightly
* misleading as there is no such thing. It may well be that the code in this
* class has to be modified to produce files to suit a specific application
* or requirement.
*
*
* @version 1.00 9th April 2010
* 1.10 13th April 2010 - Added support for processing all Excel
* workbooks in a folder along with the ability
* to specify a field separator character.
* 2.00 14th April 2010 - Added support for embedded characters; the
* field separator, EOL and double quotes or
* speech marks. In addition, gave the client
* the ability to select how these are handled,
* either obeying Excel's or UNIX formatting
* conventions.
*/
@SuppressWarnings({"java:S106","java:S4823","java:S1192"})
public class ToCSV {
private static final Logger LOG = LogManager.getLogger(ToCSV.class);
private Workbook workbook;
private ArrayList> csvData;
private int maxRowWidth;
private int formattingConvention;
private DataFormatter formatter;
private FormulaEvaluator evaluator;
private String separator;
private static final String CSV_FILE_EXTENSION = ".csv";
private static final String DEFAULT_SEPARATOR = ",";
/**
* Identifies that the CSV file should obey Excel's formatting conventions
* with regard to escaping certain embedded characters - the field separator,
* speech mark and end of line (EOL) character
*/
public static final int EXCEL_STYLE_ESCAPING = 0;
/**
* Identifies that the CSV file should obey UNIX formatting conventions
* with regard to escaping certain embedded characters - the field separator
* and end of line (EOL) character
*/
public static final int UNIX_STYLE_ESCAPING = 1;
/**
* Process the contents of a folder, convert the contents of each Excel
* workbook into CSV format and save the resulting file to the specified
* folder using the same name as the original workbook with the .xls or
* .xlsx extension replaced by .csv. This method will ensure that the
* CSV file created contains the comma field separator and that embedded
* characters such as the field separator, the EOL and double quotes are
* escaped in accordance with Excel's convention.
*
* @param strSource An instance of the String class that encapsulates the
* name of and path to either a folder containing those Excel
* workbook(s) or the name of and path to an individual Excel workbook
* that is/are to be converted.
* @param strDestination An instance of the String class encapsulating the
* name of and path to a folder that will contain the resulting CSV
* files.
* @throws java.io.FileNotFoundException Thrown if any file cannot be located
* on the filesystem during processing.
* @throws java.io.IOException Thrown if the filesystem encounters any
* problems during processing.
* @throws java.lang.IllegalArgumentException Thrown if the values passed
* to the strSource parameter refers to a file or folder that does not
* exist or if the value passed to the strDestination paramater refers
* to a folder that does not exist or simply does not refer to a
* folder.
*/
public void convertExcelToCSV(String strSource, String strDestination)
throws FileNotFoundException, IOException, IllegalArgumentException {
// Simply chain the call to the overloaded convertExcelToCSV(String,
// String, String, int) method, pass the default separator and ensure
// that certain embedded characters are escaped in accordance with
// Excel's formatting conventions
this.convertExcelToCSV(strSource, strDestination,
ToCSV.DEFAULT_SEPARATOR, ToCSV.EXCEL_STYLE_ESCAPING);
}
/**
* Process the contents of a folder, convert the contents of each Excel
* workbook into CSV format and save the resulting file to the specified
* folder using the same name as the original workbook with the .xls or
* .xlsx extension replaced by .csv. This method allows the client to
* define the field separator but will ensure that embedded characters such
* as the field separator, the EOL and double quotes are escaped in
* accordance with Excel's convention.
*
* @param strSource An instance of the String class that encapsulates the
* name of and path to either a folder containing those Excel
* workbook(s) or the name of and path to an individual Excel workbook
* that is/are to be converted.
* @param strDestination An instance of the String class encapsulating the
* name of and path to a folder that will contain the resulting CSV
* files.
* @param separator An instance of the String class that encapsulates the
* character or characters the client wishes to use as the field
* separator.
* @throws java.io.FileNotFoundException Thrown if any file cannot be located
* on the filesystem during processing.
* @throws java.io.IOException Thrown if the filesystem encounters any
* problems during processing.
* @throws java.lang.IllegalArgumentException Thrown if the values passed
* to the strSource parameter refers to a file or folder that does not
* exist or if the value passed to the strDestination paramater refers
* to a folder that does not exist or simply does not refer to a
* folder.
*/
public void convertExcelToCSV(String strSource, String strDestination,
String separator)
throws FileNotFoundException, IOException,
IllegalArgumentException {
// Simply chain the call to the overloaded convertExcelToCSV(String,
// String, String, int) method and ensure that certain embedded
// characters are escaped in accordance with Excel's formatting
// conventions
this.convertExcelToCSV(strSource, strDestination,
separator, ToCSV.EXCEL_STYLE_ESCAPING);
}
/**
* Process the contents of a folder, convert the contents of each Excel
* workbook into CSV format and save the resulting file to the specified
* folder using the same name as the original workbook with the .xls or
* .xlsx extension replaced by .csv
*
* @param strSource An instance of the String class that encapsulates the
* name of and path to either a folder containing those Excel
* workbook(s) or the name of and path to an individual Excel workbook
* that is/are to be converted.
* @param strDestination An instance of the String class encapsulating the name
* of and path to a folder that will contain the resulting CSV files.
* @param formattingConvention A primitive int whose value will determine
* whether certain embedded characters should be escaped in accordance
* with Excel's or UNIX formatting conventions. Two constants are
* defined to support this option; ToCSV.EXCEL_STYLE_ESCAPING and
* ToCSV.UNIX_STYLE_ESCAPING
* @param separator An instance of the String class encapsulating the
* characters or characters that should be used to separate items
* on a line within the CSV file.
* @throws java.io.FileNotFoundException Thrown if any file cannot be located
* on the filesystem during processing.
* @throws java.io.IOException Thrown if the filesystem encounters any
* problems during processing.
* @throws java.lang.IllegalArgumentException Thrown if the values passed
* to the strSource parameter refers to a file or folder that does not
* exist, if the value passed to the strDestination paramater refers
* to a folder that does not exist, if the value passed to the
* strDestination parameter does not refer to a folder or if the
* value passed to the formattingConvention parameter is other than
* one of the values defined by the constants ToCSV.EXCEL_STYLE_ESCAPING
* and ToCSV.UNIX_STYLE_ESCAPING.
*/
public void convertExcelToCSV(String strSource, String strDestination,
String separator, int formattingConvention)
throws FileNotFoundException, IOException,
IllegalArgumentException {
// Check that the source file/folder exists.
File source = new File(strSource);
if(!source.exists()) {
throw new IllegalArgumentException("The source for the Excel " +
"file(s) cannot be found at " + source);
}
// Ensure thaat the folder the user has chosen to save the CSV files
// away into firstly exists and secondly is a folder rather than, for
// instance, a data file.
File destination = new File(strDestination);
if(!destination.exists()) {
throw new IllegalArgumentException("The destination directory " + destination + " for the " +
"converted CSV file(s) does not exist.");
}
if(!destination.isDirectory()) {
throw new IllegalArgumentException("The destination " + destination + " for the CSV " +
"file(s) is not a directory/folder.");
}
// Ensure the value passed to the formattingConvention parameter is
// within range.
if(formattingConvention != ToCSV.EXCEL_STYLE_ESCAPING &&
formattingConvention != ToCSV.UNIX_STYLE_ESCAPING) {
throw new IllegalArgumentException("The value passed to the " +
"formattingConvention parameter is out of range: " + formattingConvention + ", expecting one of " +
ToCSV.EXCEL_STYLE_ESCAPING + " or " + ToCSV.UNIX_STYLE_ESCAPING);
}
// Copy the spearator character and formatting convention into local
// variables for use in other methods.
this.separator = separator;
this.formattingConvention = formattingConvention;
// Check to see if the sourceFolder variable holds a reference to
// a file or a folder full of files.
final File[] filesList;
if(source.isDirectory()) {
// Get a list of all of the Excel spreadsheet files (workbooks) in
// the source folder/directory
filesList = source.listFiles(new ExcelFilenameFilter());
}
else {
// Assume that it must be a file handle - although there are other
// options the code should perhaps check - and store the reference
// into the filesList variable.
filesList = new File[]{source};
}
// Step through each of the files in the source folder and for each
// open the workbook, convert its contents to CSV format and then
// save the resulting file away into the folder specified by the
// contents of the destination variable. Note that the name of the
// csv file will be created by taking the name of the Excel file,
// removing the extension and replacing it with .csv. Note that there
// is one drawback with this approach; if the folder holding the files
// contains two workbooks whose names match but one is a binary file
// (.xls) and the other a SpreadsheetML file (.xlsx), then the names
// for both CSV files will be identical and one CSV file will,
// therefore, over-write the other.
if (filesList != null) {
for(File excelFile : filesList) {
// Open the workbook
this.openWorkbook(excelFile);
// Convert its contents into a CSV file
this.convertToCSV();
// Build the name of the csv folder from that of the Excel workbook.
// Simply replace the .xls or .xlsx file extension with .csv
String destinationFilename = excelFile.getName();
destinationFilename = destinationFilename.substring(
0, destinationFilename.lastIndexOf('.')) +
ToCSV.CSV_FILE_EXTENSION;
// Save the CSV file away using the newly constricted file name
// and to the specified directory.
this.saveCSVFile(new File(destination, destinationFilename));
}
}
}
/**
* Open an Excel workbook ready for conversion.
*
* @param file An instance of the File class that encapsulates a handle
* to a valid Excel workbook. Note that the workbook can be in
* either binary (.xls) or SpreadsheetML (.xlsx) format.
* @throws java.io.FileNotFoundException Thrown if the file cannot be located.
* @throws java.io.IOException Thrown if a problem occurs in the file system.
*/
private void openWorkbook(File file) throws FileNotFoundException, IOException {
System.out.println("Opening workbook [" + file.getName() + "]");
try (FileInputStream fis = new FileInputStream(file)) {
// Open the workbook and then create the FormulaEvaluator and
// DataFormatter instances that will be needed to, respectively,
// force evaluation of forumlae found in cells and create a
// formatted String encapsulating the cells contents.
this.workbook = WorkbookFactory.create(fis);
this.evaluator = this.workbook.getCreationHelper().createFormulaEvaluator();
this.formatter = new DataFormatter(true);
}
}
/**
* Called to convert the contents of the currently opened workbook into
* a CSV file.
*/
private void convertToCSV() {
Sheet sheet;
Row row;
int lastRowNum;
this.csvData = new ArrayList<>();
System.out.println("Converting files contents to CSV format.");
// Discover how many sheets there are in the workbook....
int numSheets = this.workbook.getNumberOfSheets();
// and then iterate through them.
for(int i = 0; i < numSheets; i++) {
// Get a reference to a sheet and check to see if it contains
// any rows.
sheet = this.workbook.getSheetAt(i);
if(sheet.getPhysicalNumberOfRows() > 0) {
// Note down the index number of the bottom-most row and
// then iterate through all of the rows on the sheet starting
// from the very first row - number 1 - even if it is missing.
// Recover a reference to the row and then call another method
// which will strip the data from the cells and build lines
// for inclusion in the resylting CSV file.
lastRowNum = sheet.getLastRowNum();
for(int j = 0; j <= lastRowNum; j++) {
row = sheet.getRow(j);
this.rowToCSV(row);
}
}
}
}
/**
* Called to actually save the data recovered from the Excel workbook
* as a CSV file.
*
* @param file An instance of the File class that encapsulates a handle
* referring to the CSV file.
* @throws java.io.IOException Thrown to indicate and error occurred in the
* underylying file system.
*/
private void saveCSVFile(File file) throws IOException {
ArrayList line;
StringBuilder buffer;
String csvLineElement;
// Open a writer onto the CSV file.
try (BufferedWriter bw = Files.newBufferedWriter(file.toPath(), StandardCharsets.ISO_8859_1)) {
System.out.println("Saving the CSV file [" + file.getName() + "]");
// Step through the elements of the ArrayList that was used to hold
// all of the data recovered from the Excel workbooks' sheets, rows
// and cells.
for(int i = 0; i < this.csvData.size(); i++) {
buffer = new StringBuilder();
// Get an element from the ArrayList that contains the data for
// the workbook. This element will itself be an ArrayList
// containing Strings and each String will hold the data recovered
// from a single cell. The for() loop is used to recover elements
// from this 'row' ArrayList one at a time and to write the Strings
// away to a StringBuilder thus assembling a single line for inclusion
// in the CSV file. If a row was empty or if it was short, then
// the ArrayList that contains its data will also be shorter than
// some of the others. Therefore, it is necessary to check within
// the for loop to ensure that the ArrayList contains data to be
// processed. If it does, then an element will be recovered and
// appended to the StringBuilder.
line = this.csvData.get(i);
for(int j = 0; j < this.maxRowWidth; j++) {
if(line.size() > j) {
csvLineElement = line.get(j);
if(csvLineElement != null) {
buffer.append(this.escapeEmbeddedCharacters(
csvLineElement));
}
}
if(j < (this.maxRowWidth - 1)) {
buffer.append(this.separator);
}
}
// Once the line is built, write it away to the CSV file.
bw.write(buffer.toString().trim());
// Condition the inclusion of new line characters so as to
// avoid an additional, superfluous, new line at the end of
// the file.
if(i < (this.csvData.size() - 1)) {
bw.newLine();
}
}
}
}
/**
* Called to convert a row of cells into a line of data that can later be
* output to the CSV file.
*
* @param row An instance of either the HSSFRow or XSSFRow classes that
* encapsulates information about a row of cells recovered from
* an Excel workbook.
*/
private void rowToCSV(Row row) {
Cell cell;
int lastCellNum;
ArrayList csvLine = new ArrayList<>();
// Check to ensure that a row was recovered from the sheet as it is
// possible that one or more rows between other populated rows could be
// missing - blank. If the row does contain cells then...
if(row != null) {
// Get the index for the right most cell on the row and then
// step along the row from left to right recovering the contents
// of each cell, converting that into a formatted String and
// then storing the String into the csvLine ArrayList.
lastCellNum = row.getLastCellNum();
for(int i = 0; i <= lastCellNum; i++) {
cell = row.getCell(i);
if(cell == null) {
csvLine.add("");
}
else {
if(cell.getCellType() != CellType.FORMULA) {
csvLine.add(this.formatter.formatCellValue(cell));
}
else {
csvLine.add(this.formatter.formatCellValue(cell, this.evaluator));
}
}
}
// Make a note of the index number of the right most cell. This value
// will later be used to ensure that the matrix of data in the CSV file
// is square.
if(lastCellNum > this.maxRowWidth) {
this.maxRowWidth = lastCellNum;
}
}
this.csvData.add(csvLine);
}
/**
* Checks to see whether the field - which consists of the formatted
* contents of an Excel worksheet cell encapsulated within a String - contains
* any embedded characters that must be escaped. The method is able to
* comply with either Excel's or UNIX formatting conventions in the
* following manner;
*
* With regard to UNIX conventions, if the field contains any embedded
* field separator or EOL characters they will each be escaped by prefixing
* a leading backspace character. These are the only changes that have yet
* emerged following some research as being required.
*
* Excel has other embedded character escaping requirements, some that emerged
* from empirical testing, other through research. Firstly, with regards to
* any embedded speech marks ("), each occurrence should be escaped with
* another speech mark and the whole field then surrounded with speech marks.
* Thus if a field holds "Hello" he said then it should be modified
* to appear as """Hello"" he said". Furthermore, if the field
* contains either embedded separator or EOL characters, it should also
* be surrounded with speech marks. As a result 1,400 would become
* "1,400" assuming that the comma is the required field separator.
* This has one consequence in, if a field contains embedded speech marks
* and embedded separator characters, checks for both are not required as the
* additional set of speech marks that should be placed around ay field
* containing embedded speech marks will also account for the embedded
* separator.
*
* It is worth making one further note with regard to embedded EOL
* characters. If the data in a worksheet is exported as a CSV file using
* Excel itself, then the field will be surounded with speech marks. If the
* resulting CSV file is then re-imports into another worksheet, the EOL
* character will result in the original simgle field occupying more than
* one cell. This same 'feature' is replicated in this classes behaviour.
*
* @param field An instance of the String class encapsulating the formatted
* contents of a cell on an Excel worksheet.
* @return A String that encapsulates the formatted contents of that
* Excel worksheet cell but with any embedded separator, EOL or
* speech mark characters correctly escaped.
*/
private String escapeEmbeddedCharacters(String field) {
StringBuilder buffer;
// If the fields contents should be formatted to confrom with Excel's
// convention....
if(this.formattingConvention == ToCSV.EXCEL_STYLE_ESCAPING) {
// Firstly, check if there are any speech marks (") in the field;
// each occurrence must be escaped with another set of spech marks
// and then the entire field should be enclosed within another
// set of speech marks. Thus, "Yes" he said would become
// """Yes"" he said"
if(field.contains("\"")) {
buffer = new StringBuilder(field.replace("\"", "\\\"\\\""));
buffer.insert(0, "\"");
buffer.append("\"");
}
else {
// If the field contains either embedded separator or EOL
// characters, then escape the whole field by surrounding it
// with speech marks.
buffer = new StringBuilder(field);
if((buffer.indexOf(this.separator)) > -1 ||
(buffer.indexOf("\n")) > -1) {
buffer.insert(0, "\"");
buffer.append("\"");
}
}
return(buffer.toString().trim());
}
// The only other formatting convention this class obeys is the UNIX one
// where any occurrence of the field separator or EOL character will
// be escaped by preceding it with a backslash.
else {
if(field.contains(this.separator)) {
field = field.replaceAll(this.separator, ("\\\\" + this.separator));
}
if(field.contains("\n")) {
field = field.replace("\n", "\\\\\n");
}
return(field);
}
}
/**
* The main() method contains code that demonstrates how to use the class.
*
* @param args An array containing zero, one or more elements all of type
* String. Each element will encapsulate an argument specified by the
* user when running the program from the command prompt.
*/
public static void main(String[] args) {
// Check the number of arguments passed to the main method. There
// must be two, three or four; the name of and path to either the folder
// containing the Excel files or an individual Excel workbook that is/are
// to be converted, the name of and path to the folder to which the CSV
// files should be written, - optionally - the separator character
// that should be used to separate individual items (fields) on the
// lines (records) of the CSV file and - again optionally - an integer
// that idicates whether the CSV file ought to obey Excel's or UNIX
// convnetions with regard to formatting fields that contain embedded
// separator, Speech mark or EOL character(s).
//
// Note that the names of the CSV files will be derived from those
// of the Excel file(s). Put simply the .xls or .xlsx extension will be
// replaced with .csv. Therefore, if the source folder contains files
// with matching names but different extensions - Test.xls and Test.xlsx
// for example - then the CSV file generated from one will overwrite
// that generated from the other.
ToCSV converter;
boolean converted = true;
long startTime = System.currentTimeMillis();
try {
converter = new ToCSV();
if(args.length == 2) {
// Just the Source File/Folder and Destination Folder were
// passed to the main method.
converter.convertExcelToCSV(args[0], args[1]);
}
else if(args.length == 3) {
// The Source File/Folder, Destination Folder and Separator
// were passed to the main method.
converter.convertExcelToCSV(args[0], args[1], args[2]);
}
else if(args.length == 4) {
// The Source File/Folder, Destination Folder, Separator and
// Formatting Convention were passed to the main method.
converter.convertExcelToCSV(args[0], args[1],
args[2], Integer.parseInt(args[3]));
}
else {
// None or more than four parameters were passed so display
//a Usage message.
System.out.println("Usage: java ToCSV [Source File/Folder] " +
"[Destination Folder] [Separator] [Formatting Convention]\n" +
"\tSource File/Folder\tThis argument should contain the name of and\n" +
"\t\t\t\tpath to either a single Excel workbook or a\n" +
"\t\t\t\tfolder containing one or more Excel workbooks.\n" +
"\tDestination Folder\tThe name of and path to the folder that the\n" +
"\t\t\t\tCSV files should be written out into. The\n" +
"\t\t\t\tfolder must exist before running the ToCSV\n" +
"\t\t\t\tcode as it will not check for or create it.\n" +
"\tSeparator\t\tOptional. The character or characters that\n" +
"\t\t\t\tshould be used to separate fields in the CSV\n" +
"\t\t\t\trecord. If no value is passed then the comma\n" +
"\t\t\t\twill be assumed.\n" +
"\tFormatting Convention\tOptional. This argument can take one of two\n" +
"\t\t\t\tvalues. Passing 0 (zero) will result in a CSV\n" +
"\t\t\t\tfile that obeys Excel's formatting conventions\n" +
"\t\t\t\twhilst passing 1 (one) will result in a file\n" +
"\t\t\t\tthat obeys UNIX formatting conventions. If no\n" +
"\t\t\t\tvalue is passed, then the CSV file produced\n" +
"\t\t\t\twill obey Excel's formatting conventions.");
converted = false;
}
}
// It is not wise to have such a wide catch clause - Exception is very
// close to being at the top of the inheritance hierarchy - though it
// will suffice for this example as it is really not possible to recover
// easily from an exceptional set of circumstances at this point in the
// program. It should however, ideally be replaced with one or more
// catch clauses optimised to handle more specific problems.
catch(Exception ex) {
LOG.atWarn().withThrowable(ex).log("Unexpected exception");
converted = false;
}
if (converted) {
System.out.println("Conversion took " +
((System.currentTimeMillis() - startTime)/1000) + " seconds");
}
}
/**
* An instance of this class can be used to control the files returned
* be a call to the listFiles() method when made on an instance of the
* File class and that object refers to a folder/directory
*/
static class ExcelFilenameFilter implements FilenameFilter {
/**
* Determine those files that will be returned by a call to the
* listFiles() method. In this case, the name of the file must end with
* either of the following two extension; '.xls' or '.xlsx'. For the
* future, it is very possible to parameterise this and allow the
* containing class to pass, for example, an array of Strings to this
* class on instantiation. Each element in that array could encapsulate
* a valid file extension - '.xls', '.xlsx', '.xlt', '.xlst', etc. These
* could then be used to control which files were returned by the call
* to the listFiles() method.
*
* @param file An instance of the File class that encapsulates a handle
* referring to the folder/directory that contains the file.
* @param name An instance of the String class that encapsulates the
* name of the file.
* @return A boolean value that indicates whether the file should be
* included in the array retirned by the call to the listFiles()
* method. In this case true will be returned if the name of the
* file ends with either '.xls' or '.xlsx' and false will be
* returned in all other instances.
*/
@Override
public boolean accept(File file, String name) {
return(name.endsWith(".xls") || name.endsWith(".xlsx"));
}
}
}