[LOG4J2-1216] Nested pattern layout options broken

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.4.1, 2.9.1
• Fix Version/s: 2.10.0
• Component/s: Pattern Converters
• Labels: easyfix
• Flags: Patch
• Assignee: Unassigned
• Reporter: Thies Wellpott
• Created: 09/Dec/15 10:46
• Updated: 18/Nov/17 15:30
• Resolved: 12/Oct/17 21:45

Description

Parsing the "deeply" nested PatternLayout

%maxLen{[XXX, ${hostName}, ${web:contextPath}] %p: %c{1} - %m%notEmpty{ =>%ex{short}}}{160}

(with %maxLen being a custom Converter)

results in wrong parsing.
Patternparser.extractOptions() gets the nesting wrong.

Solution:

private static int extractOptions(final String pattern, final int start, final List<String> options) {
    int i = start;
    while (i < pattern.length()  &&  pattern.charAt(i) == '{') {
        i++;                      // skip opening "{"
        final int begin = i;      // position of first real char
        int depth = 1;            // already inside one level
        while (depth > 0  &&  i < pattern.length()) {
            char c = pattern.charAt(i);
            if (c == '{') {
                depth++;
            } else if (c == '}') {
                depth--;
            // TODO(?) maybe escaping of { and } with \ or %
            }
            i++;
        } // while

        if (depth > 0) {          // option not closed, continue with pattern on opening "{"
            return begin-1;
        }

        options.add(pattern.substring(begin, i-1));
    } // while

    return i;
}

This should also be faster than the current implementation because the pattern ist only walked once, not multiple times with indexOf().

(LOG4J2-107 is a similar but old bug)

Issue Links

• links to: GitHub Pull Request #111
• links to: GitHub Pull Request #116