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From <wapedi...@technologist.com>
Subject expression tag in JSP standar
Date Tue, 24 Jul 2001 18:15:33 GMT
Hi,

I have notice a miss-implementation of the 'expression tag' ("<%= ... 
%>") between different JSP containers witch I want to share with you to 
clarify the standar vs. implementarion.

The main issue is that an expression of type "<%= variable %> within a 
JSP page prints out different strings when 'variable' is 'null'  ((variable 
== null) is true) ('variable' is of class 'String')

Tomcat v3.2.1 prints out the string "null", while some other JSP containers 
(BEA Weblogic v6.0, HP Bluestone total-e-server v7.2) print out an empty 
string (nothing).

However an expresion of type "<%= (variable1 + variable2) %>" prints out 
the same on every container (where both variables are 'String', and 
variable1 is NOT null  and variable2 IS null)

Does anyone have an opinion on what should be the correct behave for the 
expression-tag?. Is there any missunderstanding of the JSP 
specifications/standar?. Why the "<%= .. %>" tag behaves different on 
different 
containers (same jdk 1.3.0)?.

I wonder what is the behave on other containers (iPlanet, Websphere, 
Tomcat 4, other..). Can anyone test it and give feedback?.


Here is the code I've tested:

---- jsp ------
<% String a = null;
   String b = "hello world"; %>
<html><boby> 
1 -<%=a%>-<p>
2 -<%=b%>-<p>
3 -<%=(b + a)%>-<p>
</body></html>
--------------

Results:

----- TOMCAT -----
1 -null- 
2 -hello world- 
3 -hello worldnull-
----- TOMCAT -----

----- BEA & BLUESTONE -----
1 -- 
2 -hello world- 
3 -hello worldnull-
----- BEA & BLUESTONE -----
Notice line 1 is different while 2 & 3 are equal.

Best regards
Bob.

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