File charset changes to binary in docker container

Question

I have an application which listens to the external feed on hourly basis and receives the feed JSON which is a chunked transfer encoding stream, the listener to the feed write the chunk to the file, after the whole stream is completed another thread parses the file and extracts the data. But now while writing the file the data is written in binary format even though I have specified the charset while writing.

    public void writeToFile(InputStream in){
     File feedFile = new File("/tmp/feed.json");
    try {
        FileUtils.touch(feedFile);
        StringWriter writer = new StringWriter();
        IOUtils.copy(in, writer, StandardCharsets.UTF_8);
        FileUtils.write(feedFile, writer.toString(), StandardCharsets.UTF_8,true);

    } catch (IOException e) {
        logger.error(Constants.FAILED_TO_WRITE_FEED_INTO_FILE,e);
    }
}

This code works fine on windows and linux box, but while inside docker container its written in binary format.

Docker container used Centos7

Answer 1

Maybe the locale UTF-8 in the container doesn't exist?

You can see the current locale in your running container with cat /etc/locale.conf

If it's not LANG=en_US.utf8, you can follow the instruction from this StackOverflow post by user2915097:

# Set the locale
RUN sed -i -e 's/# en_US.UTF-8 UTF-8/en_US.UTF-8 UTF-8/' /etc/locale.gen && \
    locale-gen
ENV LANG en_US.UTF-8  
ENV LANGUAGE en_US:en  
ENV LC_ALL en_US.UTF-8

Source: How to set the locale inside a Ubuntu Docker container? https://stackoverflow.com/a/28406007/3756843

EDIT 1:

You should use InputStreamReader instead of InputStream because:

• InputStream is made to handle binary data
• InputStreamReader is made to handle text

You can find more information here.