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javacharacter-encodingnio

Write a text file encoded in UTF-8 with a BOM through java.nio

I have to write the output of a database query to a csv file.

Unfortunately, many people in my company are not able to use a nice editor like Notepad++ and keep opening csv files with Excel.

When I write a text/csv file using java.nio like this

public static void main(String[] args) {
    Path path = Paths.get("U:\\temp\\TestOutput\\csv_file.csv");
    List<String> lines = Arrays.asList("Übernahme", "Außendarstellung", "€", "@", "UTF-8?");

    try {
        Files.write(path, lines, StandardCharsets.UTF_8, StandardOpenOption.CREATE_NEW);
    } catch (IOException e) {
        e.printStackTrace();
    }
}

the file gets created successfully and is encoded in UTF-8.

Now the problem is the missing BOM in that file.

There is no BOM (Notepad++ bottom-right encoding label shows UTF-8) which is no problem for Notepad++

enter image description here

but obviously it is for Excel

enter image description here

and when I use Notepad++'s option Encoding > Convert to UTF-8-BOM, save & close it and open the file in Excel afterwards, it correctly displays all the values, no encoding issues are left.

That leads to the following question:

Can I force java.nio.file.Files.write(...) to add a BOM when using StandardCharsets.UTF-8 or is there any other way in java.nio to achieve the desired encoding?

Solution

  • As far as I know, there's no direct way in the standard Java NIO library to write text files in UTF-8 with BOM format.

    But that's not a problem, since BOM is nothing but a special character at the start of a text stream represented as \uFEFF. Just add it manually to the CSV file, f.e.:

    List<String> lines = 
    Arrays.asList("\uFEFF" + "Übernahme", "Außendarstellung", "€", "@", "UTF-8?");
        ...