apache/flink · error · IllegalArgumentException

Could not split string. Illegal quoting at position: {}

Error message

Could not split string. Illegal quoting at position: {}

What it means

Thrown by StructuredOptionsSplitter.processTokens when a quoted token (single or double quoted) is immediately followed by a token that is not a delimiter. This means characters appear right after a closing quote without the expected separator, which indicates malformed quoting in a structured config value.

Source

Thrown at flink-core/src/main/java/org/apache/flink/configuration/StructuredOptionsSplitter.java:100

        if (escape) {
            return "'" + string.replaceAll("'", "''") + "'";
        }

        return string;
    }

    private static List<String> processTokens(List<Token> tokens) {
        final List<String> splits = new ArrayList<>();
        for (int i = 0; i < tokens.size(); i++) {
            Token token = tokens.get(i);
            switch (token.getTokenType()) {
                case DOUBLE_QUOTED:
                case SINGLE_QUOTED:
                    if (i + 1 < tokens.size()
                            && tokens.get(i + 1).getTokenType() != TokenType.DELIMITER) {
                        int illegalPosition = tokens.get(i + 1).getPosition() - 1;
                        throw new IllegalArgumentException(
                                "Could not split string. Illegal quoting at position: "
                                        + illegalPosition);
                    }
                    splits.add(token.getString());
                    break;
                case UNQUOTED:
                    splits.add(token.getString());
                    break;
                case DELIMITER:
                    if (i + 1 < tokens.size()
                            && tokens.get(i + 1).getTokenType() == TokenType.DELIMITER) {
                        splits.add("");
                    }
                    break;
            }
        }

        return splits;

View on GitHub (pinned to 2f3c205e92)

Solutions

Ensure quoted segments are either fully self-contained or followed by the delimiter (',' or ';' or ':').
If a value contains both quotes and delimiters, quote the entire value and escape internal quotes by doubling them.
Remove stray quote characters that don't open/close a complete segment.

Example fix

# before
my.list: 'item1'item2;item3

# after
my.list: item1;item2;item3

Defensive patterns

Strategy: validation

Validate before calling

// Quick check: after a closing quote, only a delimiter or end-of-string should follow
String v = rawValue;
for (int i = 0; i < v.length(); i++) {
    char c = v.charAt(i);
    if ((c == '\'' || c == '"')) {
        int close = v.indexOf(c, i + 1);
        if (close >= 0 && close + 1 < v.length()) {
            char next = v.charAt(close + 1);
            if (next != ',' && next != ';' && next != ':') {
                throw new IllegalArgumentException("Illegal quoting at position " + close);
            }
        }
    }
}

Try / catch

try {
    StructuredOptionsSplitter.splitEscaped(value, delimiter);
} catch (IllegalArgumentException e) {
    if (e.getMessage().contains("Illegal quoting")) { /* reformat value */ }
}

Prevention

Don't mix quoted and unquoted text in a single segment.
Quote entire values, not partial ones.
Escape internal quotes by doubling.

When it happens

Trigger: Config values like 'a'b,c (text after closing quote) or "key":value:extra where a quote is followed by non-delimiter text. The tokenizer detected a quoted segment followed by more content on the same logical segment.

Common situations: Partially quoting a value: my.list: 'item1'item2;item3. Mixing quoted and unquoted segments in a list/map value. Stray quotes from copy-paste or shell escaping leaking into the config.

Related errors

AI-assisted analysis of apache/flink@2f3c205e92 (2026-08-14). Data as JSON: /api/errors/9cc7e868427beed9. Report an issue: GitHub.