otryvanov / Windmill

A library to parse or write Excel and CSV files through a fluent API

Windmill

Windmill is a library to parse or write Excel and CSV files through a fluent API that takes advantage of Java 8 Stream and Lambda features.

Windmill targets the writing/parsing of List/Collection data. It will especially stand out for use cases like exporting/importing a result set from/to a database.

It is based on the projects Apache POI and OpenCSV to manipulate Excel and CSV files.

Getting started

Include Windmill in your project:

<dependency>
  <groupId>com.coreoz</groupId>
  <artifactId>windmill</artifactId>
  <version>1.2.0</version>
</dependency>

Import/Parsing

Here is an import example:

try (Stream<Row> rowStream = Windmill.parse(FileSource.of(new FileInputStream("myFile.xlsx")))) {
  rowStream
    // skip the header row that contains the column names
    .skip(1)
    .forEach(row -> {
      System.out.println(
        "row n°" + row.rowIndex()
        + " column 'User login' value : " + row.cell("User login").asString()
        + " column n°3 number value : " + row.cell(2).asDouble().value() // index is zero-based
      );
    });
}

Note that the try statement is required to close the Stream if the InputStream used should be closed.

Options can be passed to the parser. For example with Excel workbooks, it is possible to select the spreadsheet to use, or to specify that cell values should be trimmed:

Stream<Row> rowStream = Parsers
  .xlsx("User sheet")
  .trimValues()
  .parse(FileSource.of(new FileInputStream("myFile.xlsx")));

With CSV files, it is possible to specify multiple parameters like the charset or the escape character:

Stream<Row> rowStream = Parsers
  .csv(CsvParserConfig.builder().charset(StandardCharsets.UTF_8).separator(';').build())
  .parse(FileSource.of(new FileInputStream("myFile.csv")));

Export/Writing

Here is an export example:

Windmill
  .export(Arrays.asList(bean1, bean2, bean3))
  .withHeaderMapping(
    new ExportHeaderMapping<Bean>()
      .add("Name", Bean::getName)
      .add("User login", bean -> bean.getUser().getLogin())
  )
  .asExcel()
  .writeTo(new FileOutputStream("Export.xlsx"));

Options can be passed to the exporter, for example with CSV files, it is possible to specify multiple parameters like the separator character or the escape character:

Windmill
  .export(Arrays.asList(bean1, bean2, bean3))
  .withNoHeaderMapping(Bean::getName, bean -> bean.getUser().getLogin())
  .asCsv(ExportCsvConfig.builder().separator(';').escapeChar('"').build());
  .toByteArray();

It is also possible to export multiple tabs in one Excel workbook:

Workbook xlsxFile = new XSSFWorkbook();

Windmill
  .export(Arrays.asList(bean1, bean2, bean3))
  .withNoHeaderMapping(Bean::getName, bean -> bean.getUser().getLogin())
  .asExcel(ExportExcelConfig.fromWorkbook(xlsxFile).build("First tab"))
  .write();

Windmill
  .export(Arrays.asList(film1, film2))
  .withNoHeaderMapping(Film::getTitle, Film::getReleaseDate)
  .asExcel(ExportExcelConfig.fromWorkbook(xlsxFile).build("Second tab with films"))
  .write();

xlsxFile.write(new FileOutputStream("Export.xlsx"));