Hans Gilde wrote:
Arnaud,
You're right about how JSP works; maybe you could file an issue about this in Jelly's jira? This seems like something that many web users would want.
done (sorry for the double post #170/171, the server wasn't responding)
Currently I put the JellyContext (including the script cache) in the web session.Sorry to introduce problems but...
To get the benefit of your solution, you will need to reuse the cache between Servlet invocations. The basic Jelly Servlet does not reuse the JellyContext between invocations. Here's the pain: the context isn't entirely thread safe (actually, the parser isn't thread safe and the context uses a single parser).
Here's what you can do:
Set the HashMap into the context before invoking the script. If inherit is true (by default), the Map will be accessible throughout your entire script.
Now that your Servlet has a handle on the HashMap, you can keep it in an instance variable (must be a thread safe HashMap) or as an application variable or whatever.
When I use this JellyContext , I do a synchronized(myContext) {...} to avoid the threading problem.
Of course the cache isn't shared across session.
Your solution is better but the per-session solution has one advantage.
You can easily purge the cache when you open a new session, which is useful when you modify the jelly scripts.
I have tried to use URLConnection.getDate() to discard the cache,
but it doesn't work on the jndi URL provided by tomcat with ServletContext.getResource(), it always returns 0.
Any idea how I can manage cache update ?
-----Original Message-----
From: Arnaud Masson [mailto:[EMAIL PROTECTED] Sent: Monday, December 06, 2004 4:06 AM
To: Jakarta Commons Users List
Subject: Re: [Jelly] nested compileScript() with import ?
Hans Gilde wrote:
It's for speed, especially for Script.run().Ok, it sounds reasonable to want those caching conditions. But for my own curiosity, why do you want them? Are you in a tight memory situation or is it a perfectionist thing?
I must run many small scripts to build page, so I would like to minimize IO and XML parsing.
The outputs of the scripts are assembled in a big DOM,
under the control of a java loop which also makes some modifications to the DOM.
(I use a custom ContentHandler so that jelly output is directly added in the document without parsing.)
I think that in a classic JSP, all included pages are compiled when the main jsp is compiled,
so there is no performance penalty there. I would like the same thing in jelly.
I had the idea that the cached scripts were technical details and should not be at the same level as user variables.What's wrong with using JellyContext variables? It's pretty much what they're there for.
This time, it's probably a "perfectionist thing" ! :-)
You can think of a JellyContext as a scope. At each level of XML tag, youabove"?
get a new JellyContext (a new scope). Export says "when a variable is set
into the current scope, should I automatically put it into the scope
Inherit says "when creating a new scope, should I give it all the variables
from the current scope"?
my_imported_scripts.If a Tag wants to set a variable in a context (scope) that's higher up in the tree, there are two choices: use export=true or find the parent context (while ((parent = getParent()) != null)).
To find a variable that's been set into a context above yours, either use inherit=true or findVariable.
I'd suggest this solution:
Have your Tag find the top level context (while ((parent = getParent()) !=
null)). Use a single variable name in this context, say
That variable will be a single HashMap from uri to parsed Script instance.
Ok, I'm going to try this.
As you saw, compilable tags are sort of compiled, but they don't get ato
context or their attributes at that point. The problem with compilable tags
(I don't recommend using them) is that they're only compiled with respect
I don't think I need the advanced Script based solution for now, the cache map must be sufficient for me.the thread that compiles them. If you run the same Script in a different thread, those compiled tags won't be there. This is not true for a Script. Once a Script is compiled, it stays compiled no matter where you use it.
Thanks for your help.
isHans
-----Original Message-----
From: Arnaud Masson [mailto:[EMAIL PROTECTED] Sent: Sunday, December 05, 2004 5:06 PM
To: Jakarta Commons Users List
Subject: Re: [Jelly] nested compileScript() with import ?
Yes, I have copied the import tag and added the cache to the new tag. It works fine, but I would like to reuse compiled scripts - if several container scripts include the same sub script - if a container script include the same sub script several times
To do that, I currently use the JellyContext to cache compiled scripts with a call to setVariable(),
using a variable name based on the script uri... it works, but it's not really clean.
Maybe a better way would be to override the compileScript() methods of the JellyContext
and add a cache of compiled scripts inside the context (indexed by uri/url) ?
Also I am not sure how to handle the 'export' and 'inherit' parameters when I use compileScript+run instead of a single call to runScript().
You say a Tag isn't compilable, but what's the "CompilableTag" ??
I tried to use it the but the attributes (uri,...) of my tag are empty when "compile" is called.
Thanks for your help!
.Hans Gilde wrote:
You could easily cache the imported script the first time it's run. This
thisa simple modification to the current import tag, so that it keeps the
reference to the script. If you do this, why not add an attribute "cache"
to
turn caching on/off and then submit it as a patch to the import tag?
It would be a little harder, but not at all impossible, to make it cache
the
imported script at compile time.
If not, the basic idea is this:
A Tag isn't compilable, it's generated at runtime. A Script is compilable,
it's generated at compile time. You need a special Script, not a special
Tag. Scripts are very much like tags except that they need to be thread
safe. Most of the time, a Script called TagScript is used. By default,
Script creates and caches Tag instances when it's run.
Your new Script would compile the import at compile time. The result of
compiling the import is, it self, a Script instance. At runtime, your
Script
would simply pass control to the imported Script.
You would also have to implement a custom TagLibrary. A TagLibrary gets to create a TagScript (implements Script) for every XML tag in its namespace. So, your TagLibrary would create a custom TagScript that would compile and keep the imported XML.
-----Original Message-----
From: Arnaud Masson [mailto:[EMAIL PROTECTED] Sent: Saturday, December 04, 2004 6:07 PM
To: [EMAIL PROTECTED]
Subject: [Jelly] nested compileScript() with import ?
hi
in the current version of jelly "import" tag, it seems that imported scripts are always parsed and recompiled each time the containing script runs,
even if this script has already been compiled.
the problem is that it isn't optimized if the compiled version of the main script is cached.
is it possible to compile all scripts included via <j:import ...> via a single call to jellyContext.compileScript() on the containing script ?
should i write a custom tag to implement that (to replace import) ?
thanks in advance
arnaud
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