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From Hans Bergsten <>
Subject Incorrect code for custom actions [Was: Re: 3.2 beta status update]
Date Mon, 03 Jul 2000 03:56:36 GMT
Hans Bergsten wrote:
> [...]
> I've tested the 3.2 beta with two tag libraries that were working fine with
> Tomcat 3.1, using JDK 1.3 and JDK 1.2.2 on Windows NT. I noticed the
> following problems:
> [...]
> 3) Incorrect code generated for some custom actions.

Okay, I believe I have tracked down this problem now. But since the code for
generating the JSP implementation class is far from obvious, I would appreciate
if someone who's familiar with the code can confirm my findings.

The problem occurs in this scenario. First, the generation of the JSP
class for one page fails, due to a missing setter method for a custom action
attribute. This results in a CompileException being thrown by the
generateSetters() method. This is the expected behavior.

After this failure, though, processing of *any* page containing a custom action 
results in invalid code being generated. Example:

  com.ora.jsp.tags.counter.IncrementCounterTag _jspx_th_ora_incrementCounter_0 = 
    new com.ora.jsp.tags.counter.IncrementCounterTag();

The _jspx_th_iob_dbStore_0 variable refers to the tag handler in the first page,
i.e. the one with the missing setter method; it's not defined at all in this

The reason is that the state of a static variable in TagGeneratorBase is busted:

    static private Stack tagHandlerStack = new Stack();

This Stack seems to be intended to hold the nesting hierarchy for action
elements within a page. I have not traced through all code, but it seems like 
if the code generation goes well, the state of the Stack is maintained by an 
equal number of push() and pop() calls, but if the code generation fails, junk 
is left on the Stack.

I can't understand why this is a static variable; making it a regular instance 
variable should solve the problem since a new instance of TagGeneratorBase is 
created for each page. Having it as a static probably means that there are 
multi-threading issues as well, even though I haven't run into them yet.
There's one more static in this class:

    static private Hashtable tagVarNumbers = new Hashtable();

I'm not sure how it's used, but it can probably cause similar problems.

My suggestion is to simple make both these variables regular instance variables.
If I'm missing something, please let me know.

Hans Bergsten
Gefion Software

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