Bug 7067

Summary: EL exception message contains HTML-like elements that the browser doesn't display
Product: Taglibs Reporter: Hans Bergsten <hans>
Component: Standard TaglibAssignee: Tomcat Developers Mailing List <dev>
Status: RESOLVED INVALID    
Severity: normal    
Priority: P3    
Version: unspecified   
Target Milestone: ---   
Hardware: All   
OS: All   

Description Hans Bergsten 2002-03-13 02:00:25 UTC
When I have a syntax error in an EL expression, the exceptions contains this
text:
Unable to parse the expression:
org.apache.taglibs.standard.lang.jstl.parser.ParseException: Encountered "<EOF>"
at line 1, column 18.
Was expecting one of:

"}" ...
    "." ...
    <GT> ...
    <LT> ...
    "==" ...
    <LE> ...
    <GE> ...
    "!=" ...
    "[" ...
    "+" ...
    "-" ...
    "*" ...
    <DIVIDE> ...
    <MODULUS> ...
    "and" ...
    "or" ...

When this is displayed by the container in an HTML formatted error page (like
the one used by Tomcat 4), the <GT>, <LT> etc. operators are not displayed.
I suggest avoiding greater-than and less-than characters in all error
messages (even though this could be fixed by the container if it encoded all
exception messages).
Comment 1 Hans Bergsten 2002-03-13 07:01:55 UTC
It's extremely hard to find out which expression is invalid even in a modestly
complex page with a few expressions. The line and column number in the exception
message are confusing since they refer to the line/column in a single expression,
not a line/column in the page (which is basically impossible to accomplish in
JSP 1.2).

I suggest the complete expression being parsed be included in the exception
message. That would make it a lot easier to find out where the problem lies.
Comment 2 Hans Bergsten 2002-03-14 04:45:32 UTC
One more thought: isn't the TLV supposed to check EL syntax? If so, it should
be able to report real line numbers for syntax errors using the jsp.id element
for the action element (at least in a container that suppors jsp.id attributes).

There may still be occasional EL runtime errors, so my previous comment about
including the complete expression in the exception message still applies.
Comment 3 Nathan Abramson 2002-03-15 21:14:46 UTC
I've separated Hans' additional comments about including the complete
expression in the error message to bug 7158
Comment 4 Nathan Abramson 2002-03-20 14:08:54 UTC
Regarding the original bug (exception contains HTML-like element), I
don't think the JSTL is the right place to fix this.  This really
seems like it should be the container's responsibility, since the
container is choosing to show the exception to the end user, and
therefore should take on the responsibility of formatting the
exception correctly.

If we change our error message to be formatted to particular markup
conventions, then we're making assumptions about how the exception
will be displayed.  For example, what if it's going to be displayed in
two different formats, such as HTML and a log entry?  Unless the
container is responsible for the formatting, one of those outputs is
going to look wrong.