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From "Cindy Nordahl" <>
Subject RE: I18N: <bundle> Bug?
Date Wed, 19 Dec 2001 09:32:04 GMT
> The exception may have been thrown by a tag handler or some application
> logic (as opposed to scriplet code).

If a Tag handler throws an exception, how does it know to throw *my*
implementation of the exception (implements LocalizableException) class?  It
seems like I would have to create my own tag and tag handler.

I understand how I could get scriptlet code to call my implementation of the
exception -- I use the <exception> tag and pass in an instance of my
LocalizableException class as the value attribute and pass in the
ResourceBundle that defines my localized messages.

Would there ever be any reason to extend an already existing exception class
like javax.servlet.jsp.JspTagException and have it implement
LocalizableException?  This way, I could make it display a localized version
of the error message, like "Unparseable date" (for an English locale).  Or,
would this be overkill?

Thank you very much!


-----Original Message-----
From: Jan Luehe [mailto:Jan.Luehe@Sun.COM]
Sent: Monday, December 17, 2001 10:28 PM
Subject: Re: I18N: <bundle> Bug?

Hi Cindy:

> Thanks again for your detailed response.
> I'm having trouble grasping the <exception> tag.  This is how I think it
> should work:
> Let's say that I create my own exception class that implements
> LocalizableException, called FormValidatorException.
> A user fills out a form on a web page.  They make some mistakes while
> entering the data -- the password they chose isn't long enough and some
> required fields are left blank.
> When the form is submitted, I check to see if the password is invalid:
> <%
> FormValidatorException pwExcptn = new FormValidatorException();
> pageContext.setAttribute("pwExcptn ",pwExcptn);
> FormValidatorException reqExcptn = new FormValidatorException();
> pageContext.setAttribute("reqExcptn ",reqExcptn );
> %>
> <c:if test = "$passwordInvalid">
>   <c:exception value="$pwExcptn" bundle="$errorBundle"/>
> </c:if>
> <c:if test = "$nameFieldEmpty">
>   <c:exception value="$reqExcptn" bundle="$errorBundle"/>
> </c:if>
> Am I on the right track?  I'm wondering how the right localized string is
> accessed from the errorBundle.  How does it know when to display the error
> message for an invalid password?

Actually, the main purpose of the <exception> tag is to display
an exception message in its localized form in an error page.
The exception may have been thrown by a tag handler or some application
logic (as opposed to scriplet code).

By implementing the LocalizableException interface, your exception
provides information about the message key to be looked up in the
resource bundle (see getMessageKey() interface method) and the
parameters (if any) for parametric replacement (see getMessageArgs()
method). This information must be supplied to your exception's constructor.

Hope this helps.


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