jstl - "${fn:escapeXml(parameter)!=null}" is always true -

i checking parameter!=null using ${fn:escapexml},

but returns true me.

e.g <c:set var="isabc" value="${fn:escapexml(param.isabc)!=null}"/>

when exscape function removed, return false if parameter null.

e.g <c:set var="isabc" value="${param.isabc!=null}"/>

i know reason, lot.

the reason simple: escapexml() returns empty string when called null. , empty string not null.

public static string escapexml(string input) {     if (input == null) return "";     return util.escapexml(input); }