Unexpected quotes in header column name

[HongliBu]

Hi we I using the lib(dependency "com.fasterxml.jackson.dataformat:jackson-dataformat-csv:2.9.9") to write Java Map Object to CSV files, I am seeing a weird thing. some of the header column generated are wrapped in double quotes.
like this:
create_timestamp,detection_timestamp,document_major_version,duplicate_count,env,event_guid,event_timestamp,finding_source_id,finding_source_system,finding_timestamp,finding_unique_id,landing_timestamp,"record_processed_timestamp","security_event_manager_id",sem_state,update_timestamp

and my code is like this:

private static class StreamHolder {
        private final FileOutputStream outputStream;
        private final File outputFile;
        private final CsvSchema csvSchema;
        private final CsvMapper csvMapper;


        StreamHolder(File outputFile, Map<String, Object> fields) {
            this.outputFile = outputFile;
            CsvSchema.Builder schemaBuilder = new CsvSchema.Builder();
            csvMapper = new CsvMapper();
            SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS");
            csvMapper.setDateFormat(df);
            for (String value : new TreeSet<>(fields.keySet())) {
                schemaBuilder.addColumn(value, CsvSchema.ColumnType.STRING);
            }
            csvSchema = schemaBuilder.build();
            try {
                this.outputStream = new FileOutputStream(outputFile);
            } catch (IOException e) {
                throw new PublisherException("Open stream on " + outputFile, e);
            }
        }

        void write(Map<String, Object> fields) throws IOException {
            if (outputFile.length() == 0) {
                outputStream.write(csvMapper.writerFor(Map.class).
                        with(csvSchema.withHeader()).writeValueAsBytes(fields));
            } else {
                outputStream.write(csvMapper.writerFor(Map.class).
                        with(csvSchema.withoutHeader()).writeValueAsBytes(fields));

            }
        }}

here I defined a class, and will be called to generated an instance and maintain the instance to write data to csv file. I use addColumn to define a schema. And when writing I use a Map<String, Object> fields as the input, and if the file is empty I useHeader, o.w. I don't useHeader.

The keys are all string type, why some of the keys has double quotes?

[cowtowncoder]

Ok, first a note: 2.9.9 is bit of an old versions, so typically for issues it is good to check a more recent version; in this case either 2.11.4 or 2.12.0. But I assume there is no difference in behavior.
Since CSV allows quoting of any and all values (and requires in some cases; users may prefer in others as well), behavior seen is legal. But I am guessing you find it unexpected that only 2 column names are quoted. I have not verified this but I suspect this is because by default Jackson uses heuristics where:

1. For short Strings, check is made to see if quoting is needed; if not, left unquoted (unless quoting is forced)
2. For longer Strings, quoting occurs automatically: this to avoid cost of iterating over the whole String value to verify the need.

Definition of "short" String is in CsvEncoder class:

    /**
     * Also: only do check for optional quotes for short
     * values; longer ones will always be quoted.
     */
    final protected static int MAX_QUOTE_CHECK = 24;

so Strings 24 characters or longer are quoted by default.

But you can force checking of all values by enabling

 JsonGenerator.Feature.STRICT_CHECK_FOR_QUOTING

after which check would be made for longer names too and quoting not used unless absolutely required (due to existence of characters like linefeeds).