If doEndTag isn't a good option for cleaning, why don't you use doFinally()? Anyway, it's incredible... i'm always finding out that writing custom tags is a real nightmare :-)
On Mon, 2003-02-03 at 15:30, Tim Moore wrote: > > -----Original Message----- > > From: Gary McGath [mailto:[EMAIL PROTECTED]] > > Sent: Monday, February 03, 2003 9:14 AM > > To: [EMAIL PROTECTED] > > Subject: Custom tag life cycle > > > > > > The webapp which I am developing (see http://www.timeczar.com for > > details) uses a moderately complex custom tag library, and > > I've found the lifecycle of a TagSupport object to be very confusing. > > > > As I understand it, a TagSupport object may (but is not > > guaranteed to) be reused for subsequent occurrences of the > > same tag in a JSP. This means that attribute variables can't > > safely be initialized in the constructor, because they may > > not get reinitialized for subsequent occurrences of the tag. > > (Here I'm assuming that setter functions for attributes > > simply set an instance variable.) > > > > After some digging, I found that the recommended way to reset > > attribute instance varaibles is to use the doEndTag method. > > This probably doesn't work if a tag is nested within a tag of > > the same name, but I can live with that. > > Actually I believe that containers would be required to use two > different instances when tags are nested. The instance can only be > reused for subsequent uses of the tag *after* the first one is closed. > > But I would do the initialization in doStartTag rather than doEndTag. > The latter may not be called if an exception is thrown from within the > tag body. > > > > > Doing this works fine in Tomcat. However, I recently ported > > my webapp to Resin and found that it doesn't work there. > > Here's a cut-back excerpt from my JSP: > > > > <caltags:eventset> > > <caltags:evtstartdate mode="date" length="m"/> - > > <caltags:evtenddate mode="date" length="m"/> </caltags:eventset> > > > > The class which implements eventset includes the tag body > > once for each event in the set. The evtstartdate and > > evtenddate tags are implemented by a class called DateTag, > > which extends TagSupport. Under Tomcat, DateTag.setMode and > > DateTag.SetLength get called once for each tag in each > > inclusion of the tag body. Under Resin, only two calls (one > > for each of the date tags) are made to each of setMode and > > setLength. If I clear the mode and length fields when I call > > doEndTag, then all occurrences of the date tags except the > > first take on their default attributes, which is not the > > behavior I want. > > > > Are both Tomcat and Resin within spec in implementing > > different behaviors here? If so, what is the correct point > > in the lifecycle to reset attribute values in a TagSupport object? > > The spec allows the container to assume that the attributes of a tag > handler will be retained across invocations, so if there are multiple > identical invocations, the setter methods do not need to be called > again. > > Here's what I'd recommend: > > Initialize the mode and length instance variables to null at > construction time. > > Do something like this in doStartTag: > > String mode = this.mode; > if (mode == null) { > mode = DEFAULT_MODE; > } > > ...and repeat for length. Never modify the instance variables or call > their setters yourself -- let the container manage them. > > -- > Tim Moore / Blackboard Inc. / Software Engineer > 1899 L Street, NW / 5th Floor / Washington, DC 20036 > Phone 202-463-4860 ext. 258 / Fax 202-463-4863 > > --------------------------------------------------------------------- > To unsubscribe, e-mail: [EMAIL PROTECTED] > For additional commands, e-mail: [EMAIL PROTECTED] > -- Felipe Schnack Analista de Sistemas [EMAIL PROTECTED] Cel.: (51)91287530 Linux Counter #281893 Centro Universitário Ritter dos Reis http://www.ritterdosreis.br [EMAIL PROTECTED] Fone/Fax.: (51)32303341 --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
