DatatypeConverter.parseBoolean converts invalid strings to true

[johannesherr]

The method parseBoolean in javax.xml.bind.DatatypeConverterImpl is supposed to convert only the values "true" and "1" to true (while ignoring leading and trailing whitespace). It, however, converts all strings to true that start with "tru" and are 4-5 characters long. For example:

DatatypeConverter.parseBoolean("trux"); // -> true
DatatypeConverter.parseBoolean("truu"); // -> true
DatatypeConverter.parseBoolean("truxx"); // -> true
DatatypeConverter.parseBoolean("truuu"); // -> true

This is caused by these segments in parseBoolean:

case 't':
    String strTrue = "rue";
    do {
        ch = literal.charAt(i++);
    } while ((strTrue.charAt(strIndex++) == ch) && i < len && strIndex < 3);

    if (strIndex == 3) {
        value = true;
    } else {
        return false;
    }

and:

if (i < len) {
    do {
        ch = literal.charAt(i++);
    } while (WhiteSpaceProcessor.isWhiteSpace(ch) && i < len);
}

if (i == len) {
    return value;
} else {
    return null;
}

In the first snippet value is assigned true also when the loop was left after comparing the third character, because the expression strTrue.charAt(strIndex++) == ch was false (that is when there is as mismatch between 'e' and the current character). strIndex will still be 3 (because it is incremented unconditionally).

That explains why "trux" is converter to true. The second snippet explains why the additional character in "truxx" is also ignored. If we haven't read the input completely the second input checks if there is whitespace to ignore. However it also uses an unconditional increment of the reading position, which causes the code to skip over the offending last character. Therefore i == len holds and the previously assigned true is returned.

[antoniosanct]

Hi, @johannesherr:
According to DatatypeConverterImpl javadoc, this class is deprecated and it would remove at any moment. In fact, the same comment recommends the use of jakartaee/jaxb-api version. Please, open an issue in this project.

https://github.com/jakartaee/jaxb-api/blob/master/api/src/main/java/jakarta/xml/bind/DatatypeConverterImpl.java

A possible solution:

case 't':
    String strTrue = "rue";
    do {
        ch = literal.charAt(i++);
    } while ((strTrue.charAt(strIndex++) == ch) && i < len && strIndex < 3);

    if (strTrue.charAt(strIndex-1) == literal.charAt(i-1)) {
        value = true;
    } else {
        return false;
    }

Regards,
Antonio.