jsp - JSTL Formatting: Confusing IllegalargumentException -

i have object formatobject in session scope, member of type simpledateformat sdf based on pattern "dd.mm.yyyy hh:mm:ss".

i want use jstl formatting tag library format output:

<fmt:formatdate value="${dataobject.date}" pattern="${formatobject.sdf}"/> 

this gives me following exception:

org.apache.jasper.jasperexception: java.lang.illegalargumentexception: illegal pattern character 'j' 

when try following, works expected:

<fmt:formatdate value="${dataobject.date} pattern="dd.mm.yyyy hh:mm:ss"/> 

confusing ... have idea?

the pattern attribute has refer string representing pattern, not concrete simpledateformat instance constructed around pattern.

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unrelated concrete problem, simpledateformat not threadsafe, yet attempt implies it's been created in constructor of formatobject , reused session/application wide. not right. simpledateformat must declared , created on thread local basis (i.e. inside method block). pattern part can constant.

so, all, right:

public class formatter {      private static final string pattern = "dd.mm.yyyy hh:mm:ss";      public string format(date date) { // example. no idea how you're further using it.         return new simpledateformat(pattern).format(date); // create simpledateformat in method local scope. never create instance variable.     }      public string getpattern() {         return pattern;     }  } 

with

<fmt:formatdate ... pattern="#{formatter.pattern}" />