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Posted to user@struts.apache.org by Murray Collingwood <mu...@focus-computing.com> on 2005/08/19 07:25:39 UTC
Using custom tags and struts together
Hello all
Has anybody successfully used Stuts tags and Custom tags together?
For example:
Consider a custom tag with the following code:
out.println("<html:link action=\"Update.do\">" + entry[ix] + "</html:link>");
The custom tag appears to write the output directly to the socket without further Struts
tag evaluation, consequently the HTML source on the browser includes "html:link" which
it doesn't understand.
1. How about writing the link using <a href=/WEB-INF/pages/update.jsp>....</a>
When I do this I lose the connection to my current session. Not a solution.
2. Try return true in the "theBodyShouldBeEvaluatedAgain" method.
I tried this and the code got into a loop (I believe this simply recurses back through my
code). If I am supposed to use this somebody will need to tell me a simple way of
stopping the recursion.
3. The only other alternative I have is to look into the Struts source code and try and
find some internal method to call to evaluate the generated code before I print it to the
socket.
Hope somebody has tried to do this before...
Kind regards
mc
FOCUS Computing
Mob: 0415 24 26 24
murray@focus-computing.com
http://www.focus-computing.com
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Re: Using custom tags and struts together
Posted by Dave Newton <ne...@pingsite.com>.
Murray Collingwood wrote:
>I could use a <logic:greaterThan...> tag to test the value of the security number and
>then display the link if appropriate. This gets more complicated when the security
>number 3 is used, as then I have to test values on the record as well, suddenly I have
>nested <logic:..> tags and the page is starting to look a lot more complicated than it
>should. The other problem with this approach is: "whether a user can update a record
>or not" is a business logic decision and shouldn't be in the interface.
>
>Now, to complicate it even further, security number 2 is allowed to update records but
>uses a different form, in other words, they are only allowed to update certain values on
>the record. Hence I have to vary the link generated in some instances.
>
>
If the pages are radically different then perhaps you could use
completely different presentations based on a user's access
level--rather than passing a different result set to the page,
generating different links, etc. you could just send them to an entirely
different JSP.
I've found that once my page logic goes beyond a simple "show this chunk
or don't" it's been easier (not always cleaner, I suppose) to have
completely separate pages altogether. That said, I've only rarely had to
go that far: usually passing a different collection in to the JSP,
setting a true/false to choose between two links, etc. has been enough.
I'm interested in how other folks have dealt with similar issues.
Dave
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Re: Using custom tags and struts together
Posted by Murray Collingwood <mu...@focus-computing.com>.
Thanks Wendy
I think the idea of using a security bean is what I need to do.
Kind regards
mc
On 20 Aug 2005 at 9:50, Wendy Smoak wrote:
> > I hope you are getting the picture. This is why I was trying to use a
> > custom tag that could still interact with my model, call business methods
> > to make security
> > decisions and vary the generated link accordingly.
> >
> > And finally the question: How should I go about writing the "Update" link
> > now that we all understand the problem?
>
> You could put all that logic somewhere else, perhaps in a bean with an
> 'isUpdateAllowed' method:
> <c:if test="${security.updateAllowed}> <html:link ...> </c:if>
>
> Since you're already okay with a custom tag, what about extending the Struts
> link tag to do what you need?
>
> I also wonder if you really need <html:link> for this-- you're already
> hard-coding the action name. If there's nothing dynamic about the link
> other than that 'entry[ix]' part, then can you just write out the <a
> href="..."> from your custom tag?
>
> I've had success with request.isUserInRole-- *without* getting into custom
> Realms and CMA-- just add a Filter, wrap the request and override
> 'isUserInRole'. It sounds like you have some "levels" that could be roles.
> (I'm not clear on the runtime checking of fields you mentioned, but you
> should have access to the request and session from isUserInRole.) Struts
> has <logic:present role="..."> (and there's probably a JSTL equivalent).
>
> --
> Wendy Smoak
>
>
>
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murray@focus-computing.com
http://www.focus-computing.com
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Re: Using custom tags and struts together
Posted by Wendy Smoak <ja...@wendysmoak.com>.
> I hope you are getting the picture. This is why I was trying to use a
> custom tag that could still interact with my model, call business methods
> to make security
> decisions and vary the generated link accordingly.
>
> And finally the question: How should I go about writing the "Update" link
> now that we all understand the problem?
You could put all that logic somewhere else, perhaps in a bean with an
'isUpdateAllowed' method:
<c:if test="${security.updateAllowed}> <html:link ...> </c:if>
Since you're already okay with a custom tag, what about extending the Struts
link tag to do what you need?
I also wonder if you really need <html:link> for this-- you're already
hard-coding the action name. If there's nothing dynamic about the link
other than that 'entry[ix]' part, then can you just write out the <a
href="..."> from your custom tag?
I've had success with request.isUserInRole-- *without* getting into custom
Realms and CMA-- just add a Filter, wrap the request and override
'isUserInRole'. It sounds like you have some "levels" that could be roles.
(I'm not clear on the runtime checking of fields you mentioned, but you
should have access to the request and session from isUserInRole.) Struts
has <logic:present role="..."> (and there's probably a JSTL equivalent).
--
Wendy Smoak
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Re: Using custom tags and struts together
Posted by Murray Collingwood <mu...@focus-computing.com>.
Thanks for the responses to my question.
I agree totally with what you are saying, to try generating Struts tags from a Custom tag
is completely the wrong approach - I can see that now (you know, "I see the light" :-)
Let me explain what I am trying to do, maybe somebody can point me in the right
direction.
My website provides a login capability and each user has a security setting, this is just a
number (security isn't too complicated). Number 0 can simply browse around and make
comments etc. Security number 5 is allowed to manage the content, add and update
database records that contain data that appear on the site. Number 3 is allowed similar
content management access but only on certain records.
When I display a page that contains some database records I then want to display
"Update" and "Delete" links next to the appropriate data.
I could use a <logic:greaterThan...> tag to test the value of the security number and
then display the link if appropriate. This gets more complicated when the security
number 3 is used, as then I have to test values on the record as well, suddenly I have
nested <logic:..> tags and the page is starting to look a lot more complicated than it
should. The other problem with this approach is: "whether a user can update a record
or not" is a business logic decision and shouldn't be in the interface.
Now, to complicate it even further, security number 2 is allowed to update records but
uses a different form, in other words, they are only allowed to update certain values on
the record. Hence I have to vary the link generated in some instances.
I hope you are getting the picture. This is why I was trying to use a custom tag that
could still interact with my model, call business methods to make security decisions and
vary the generated link accordingly.
And finally the question: How should I go about writing the "Update" link now that we all
understand the problem?
Thanks in advance.
Kind regards
mc
On 19 Aug 2005 at 15:30, Craig McClanahan wrote:
> On 8/18/05, Murray Collingwood <mu...@focus-computing.com> wrote:
> > Hello all
> >
> > Has anybody successfully used Stuts tags and Custom tags together?
> >
> > For example:
> > Consider a custom tag with the following code:
> > out.println("<html:link action=\"Update.do\">" + entry[ix] + "</html:link>");
> >
>
> Your question doesn't really describe what you are illustrating ...
> which appears to be that you want to dynamically create a *JSP* page,
> then have the page compiled and executed, on every request. You're
> going to find that this solution is not practical, and that you should
> take another approach.
>
> When you first start a webapp, you notice the slight delay when you
> access a JSP page the first time, so that it gets compiled? Even if
> you jumped through all the technical hoops to output a JSP file and
> get it compiled (technically feasible), you're going to be imposing
> that kind of overhead on *every* request, instead of just the first
> request for that page. Even if everything else in your app was
> instantaneous, the response time of your app would be awful.
>
> A far better approach for the particular case you are using here is to
> use either an expression or some subordinate tag to calculate the
> dynamic part of your output. Assume for a moment that your Struts
> action puts the "entry" array into request scope. Now you can do
> something like:
>
> <html:link action="Update.do">
> <c:out value="${entry[3]}"/>
> </html:link>
>
> Of course, the reason you probably want to do this in the first place
> is that you want to create a bunch of links ... so put the same sort
> of structure inside a looping tag (renaming the request scope
> attribute containing your array to be "entries" to be more readable):
>
> <c:forEach var="entry" items="entries">
> <html:link action="Update.do">
> <c:out value="$entry"/>
> </html:link>
> </c:forEach>
>
> The <c:forEach> tag exposes the current element in the array as a page
> scope attribute named by the "var" attribute, and you can therefore
> reference the current element directly inside the loop.
>
> Craig
>
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>
>
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> Checked by AVG Anti-Virus.
> Version: 7.0.338 / Virus Database: 267.10.13/78 - Release Date: 19/08/2005
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FOCUS Computing
Mob: 0415 24 26 24
murray@focus-computing.com
http://www.focus-computing.com
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Re: Using custom tags and struts together
Posted by Wendy Smoak <ja...@wendysmoak.com>.
From: "Murray Collingwood" <mu...@focus-computing.com>
> Has anybody successfully used Stuts tags and Custom tags together?
>
> For example:
> Consider a custom tag with the following code:
> out.println("<html:link action=\"Update.do\">" + entry[ix] +
> "</html:link>");
I haven't done anything with custom tags in a while, but isn't this the same
as writing (in a JSP):
<my:tag attr="<other:tag action="abc"/>"/>
? Which, as you've noted, won't work.
What does your custom tag do? The 'entry[ix]' looks like it might be
iterating. If so... can you do it with <c:forEach> and <html:link> alone?
Alternately, do you really need the <html:link> or can you just write an <a
href="..."> directly?
--
Wendy Smoak
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Re: Using custom tags and struts together
Posted by Craig McClanahan <cr...@gmail.com>.
On 8/18/05, Murray Collingwood <mu...@focus-computing.com> wrote:
> Hello all
>
> Has anybody successfully used Stuts tags and Custom tags together?
>
> For example:
> Consider a custom tag with the following code:
> out.println("<html:link action=\"Update.do\">" + entry[ix] + "</html:link>");
>
Your question doesn't really describe what you are illustrating ...
which appears to be that you want to dynamically create a *JSP* page,
then have the page compiled and executed, on every request. You're
going to find that this solution is not practical, and that you should
take another approach.
When you first start a webapp, you notice the slight delay when you
access a JSP page the first time, so that it gets compiled? Even if
you jumped through all the technical hoops to output a JSP file and
get it compiled (technically feasible), you're going to be imposing
that kind of overhead on *every* request, instead of just the first
request for that page. Even if everything else in your app was
instantaneous, the response time of your app would be awful.
A far better approach for the particular case you are using here is to
use either an expression or some subordinate tag to calculate the
dynamic part of your output. Assume for a moment that your Struts
action puts the "entry" array into request scope. Now you can do
something like:
<html:link action="Update.do">
<c:out value="${entry[3]}"/>
</html:link>
Of course, the reason you probably want to do this in the first place
is that you want to create a bunch of links ... so put the same sort
of structure inside a looping tag (renaming the request scope
attribute containing your array to be "entries" to be more readable):
<c:forEach var="entry" items="entries">
<html:link action="Update.do">
<c:out value="$entry"/>
</html:link>
</c:forEach>
The <c:forEach> tag exposes the current element in the array as a page
scope attribute named by the "var" attribute, and you can therefore
reference the current element directly inside the loop.
Craig
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Re: Using custom tags and struts together
Posted by Laurie Harper <la...@holoweb.net>.
Murray Collingwood wrote:
> Hello all
>
> Has anybody successfully used Stuts tags and Custom tags together?
>
> For example:
> Consider a custom tag with the following code:
> out.println("<html:link action=\"Update.do\">" + entry[ix] + "</html:link>");
>
> The custom tag appears to write the output directly to the socket without further Struts
> tag evaluation, consequently the HTML source on the browser includes "html:link" which
> it doesn't understand.
This says 'write the text "<html:link ..." to the HTTP response', as you
say. It seems that what you are trying to do is create a custom tag which
outputs JSP source, which you then want processed as if it had appeared
literally in the JSP page. In other words, you want to write '<x:mytag/>'
in the JSP and have the rendered result be as if you'd actually written
'<html:link ...'. Is that right?
> 1. How about writing the link using <a href=/WEB-INF/pages/update.jsp>....</a>
> When I do this I lose the connection to my current session. Not a solution.
What do you mean by 'loose the connection to my current session?' Do you
mean that when the link is clicked the resulting request isn't associated
with the session? If cookies are enabled it should be, but if cookies are
turned off you need to include the session ID in the URL the same as Struts
and JSTL tags do.
> 2. Try return true in the "theBodyShouldBeEvaluatedAgain" method.
> I tried this and the code got into a loop (I believe this simply recurses back through my
> code). If I am supposed to use this somebody will need to tell me a simple way of
> stopping the recursion.
Evaluate Body is used when you want the body of the tag to be evaluated,
not when you want the /output/ of the tag to be evaluated. Think, for
example, of forEach and the like.
> 3. The only other alternative I have is to look into the Struts source code and try and
> find some internal method to call to evaluate the generated code before I print it to the
> socket.
I think it would help to take a step back and describe the overall problem
you're trying to solve. If I understand you correctly, you're trying to
write a custom tag that generates JSP source code and have that generated
JSP code evaluated inline as part of the same processing cycle that calls
your custom tag. I suspect there are easier ways to do what you need...
If all you want to do is include a link in the HTML (not JSP) markup
generated by your tag and ensure that link includes JSESSIONID when needed,
try looking at the code for the <html:link/> tag to see how the session ID
and URL rewriting is handled.
HTH,
L.
--
Laurie Harper
Open Source advocate, Java geek: http://www.holoweb.net/laurie
Founder, Zotech Software: http://www.zotechsoftware.com/
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Re: Using custom tags and struts together
Posted by Jeremiah Johnson <jo...@egr.msu.edu>.
Normally it doesn process html:link. Did you put the tld for html:link
on the page? Does your tag extend BodyTagSupport? I think I remember
having to execute the print in doEndTag() as well.
Murray Collingwood wrote:
> Hello all
>
> Has anybody successfully used Stuts tags and Custom tags together?
>
> For example:
> Consider a custom tag with the following code:
> out.println("<html:link action=\"Update.do\">" + entry[ix] + "</html:link>");
>
> The custom tag appears to write the output directly to the socket without further Struts
> tag evaluation, consequently the HTML source on the browser includes "html:link" which
> it doesn't understand.
>
> 1. How about writing the link using <a href=/WEB-INF/pages/update.jsp>....</a>
> When I do this I lose the connection to my current session. Not a solution.
>
> 2. Try return true in the "theBodyShouldBeEvaluatedAgain" method.
> I tried this and the code got into a loop (I believe this simply recurses back through my
> code). If I am supposed to use this somebody will need to tell me a simple way of
> stopping the recursion.
>
> 3. The only other alternative I have is to look into the Struts source code and try and
> find some internal method to call to evaluate the generated code before I print it to the
> socket.
>
> Hope somebody has tried to do this before...
>
> Kind regards
> mc
>
>
>
> FOCUS Computing
> Mob: 0415 24 26 24
> murray@focus-computing.com
> http://www.focus-computing.com
>
>
>
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