Add sensible defaults to StaxUtils's MAX_ELEMENT_COUNT and MAX_XML_CHARACTERS

[reta]

Add sensible defaults to StaxUtils's MAX_ELEMENT_COUNT and MAX_XML_CHARACTERS

[coheigea]

@reta Some comments from Claude:

1. maxElementCount default overflows (blocking)

getLong(MAX_ELEMENT_COUNT, Math.max(100 * MAX_CHILD_ELEMENTS_VAL, 50000));

MAX_CHILD_ELEMENTS_VAL is an int, so 100 * ... is int arithmetic — the widening to long only happens after Math.max(int,int) has returned. It overflows once maxChildElements > 21_474_836:

maxChildElements	resulting MAX_ELEMENT_COUNT_VAL
50 000 (default)	5 000 000
30 000 000	50 000
Integer.MAX_VALUE	50 000 (100 * Integer.MAX_VALUE wraps to -100, so the floor wins)

That inverts the invariant the comment states — the total element count ends up well below the per-parent child count. It also hits precisely the users most likely to notice: getInteger/getLong coerce negatives back to the default, so there is no -1 escape hatch and raising maxChildElements is the only way to relax that limit today. Anyone doing so would silently pick up a 50 000 total-element cap on upgrade.

One character:

getLong(MAX_ELEMENT_COUNT, Math.max(100L * MAX_CHILD_ELEMENTS_VAL, 50000L));

2. Derive maxXMLCharacters from MAX_TEXT_LENGTH_VAL

Your rationale above is "2x of MAX_TEXT_LENGTH" and the new code comment says the two "should be aligned", but the code hardcodes 256Mb — so the alignment breaks as soon as anyone sets org.apache.cxf.stax.maxTextLength. Raise it to 512Mb and the document-wide character cap is smaller than a single permitted text segment: a contradictory config that worked fine before this change.

private static final long MAX_XML_CHARS_VAL =
        getLong(MAX_XML_CHARACTERS, 2L * MAX_TEXT_LENGTH_VAL); // 256Mb by default

Same default (2 x 128Mb), stays correct under reconfiguration, and makes the comment true rather than aspirational. If you'd rather keep the literal, at least 256L * 1024 * 1024 so a future bump doesn't overflow.

[reta]

Thanks @coheigea

1. maxElementCount default overflows (blocking)

I will widen it to long, thanks!

2. Derive maxXMLCharacters from MAX_TEXT_LENGTH_VAL

The straight derivation does not make sense here to be fair. MAX_TEXT_LENGTH_VAL is really large by default, but we should not use multipliers there (ideally, I would think of MAX_TEXT_LENGTH_VAL as 8k and MAX_XML_CHARACTERS as 32Mb fe), so 256Mb is just reasonably large value that is not in conflict with MAX_TEXT_LENGTH_VAL default.