We are using a h:inputText in a JSF page which is bound to an Integer property (and thus can accept null). When there is no value written in the h:inputText, the form is submitting a 0 instead of null. We are using Trinidad 1.2.2 and Tomcat 6.0.20 (we also tried with Tomcat 6.0.14 as we read that this could happen with certains Tomcat versions).
How is this caused and how can I solve it?
This "feature" was result of a bugfix in EL which was introduced as per Tomcat 6.0.16. As per chapter 1.18.3 of the EL specification, a value of number type which is null should be coerced to 0. Before Tomcat 6.0.16 this was "incorrectly" been coerced to an empty string.
After all, an empty string was actually much more intuitive than a zero. The Tomcat guys at Apache got a lot complaints about this bugfix, so they introduced a new configuration setting in flavor of a VM argument as per Tomcat 6.0.17 which would disable this bugfix.
-Dorg.apache.el.parser.COERCE_TO_ZERO=false
I've by the way requested a change to this spec that it should only coerce empty/null primitive types to zero and empty/null non-primitive java.lang.Number types to empty string: JSP EL issue 184. They did not much with it, but the issue at least got a lot of votes. Who knows... This behaviour is at least indeed pretty annoying because it's non-intuitive.
See also:
来源：https://stackoverflow.com/questions/3116517/hinputtext-which-is-bound-to-integer-property-is-submitting-value-0-instead-of