appropriate time to cache component output

[Danny Mandel <dm...@tolweb.org>]

Hi all.  I'm wondering if anyone currently has any sort of caching 
systems in place to cache output for particular components given 
particular inputs.  Ideally I would like my completed component to 
function something like this:

<span jwcid="@Conditional" condition="ognl:ifCachedOutputExists">
    // Insert the cached content here
</span>
<span jwcid="@Conditional" condition="ognl:!ifCachedOutputExists">
    // Perform some expensive calculations and db fetches and at the end 
of this computation
    // insert the ouput of this conditional into some cache
</span>

I guess I have 2 main questions:
1) Is there a particular hook in the page/component render cycle that 
would be an appropriate place to insert this cache insert logic?
2) If such a hook exists, is there a way for a component to be aware of 
the html it has just rendered?

Thanks,
Danny

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Re: appropriate time to cache component output

[Kurt Zoglmann <zo...@yahoo.com>]

I'm not aware of any direct accessible caching mechanisms that you can 
use from within the tapestry framework. However, your in luck because 
there are several free caching mechanisms already implemented for you. 
Take a look at JCS, EHCache, and OSCache for caching within a single 
JVM both in disk and memory or look at SwarmCache for caching in a 
cluster. I don't know too much about all of them, but I have used 
EHCache and found it very easy to use and configure.

You may also want to take a look at hibernate. It is a ORM (Object 
relational mapping framework) and has built in support for both session 
level caching and secondary caching. If you are performing very 
expensive queries, hibernate even supports query caching. I started 
using hibernate a couple of months ago and have found that it has many 
benefits. If you just a single page that needs to have its results 
cached, I wouldn't go to all the trouble of investigating hibernate.

I've already posted something about general caching using Tapestry. 
Below is what I originally suggested for someone wanting to do server 
side include caching. Instead of caching raw output, you could manage 
your own property that has the results of the expensive computations 
and use caching on that property.

include.html
<span jwcid="@Insert" value="ognl:content" raw="true"/>

include.jwc
<component-specification class="package.Include" allow-body="yes" 
allow-informal-parameters="no">
   <parameter name="name" type="java.lang.String" required="true"/>

   <property-specification name="content" type="java.lang.String"/>
</component>

Include.java

//use JCS or EHcache to store/cache stuff

protected void prepareForRender() {
   String content;
   //check if in cache
   //load from filesystem if not in cache and place in cache
   setContent(content);
}

public abstract void setContent(String content);
public abstract String getName();


On Sep 21, 2004, at 1:19 PM, Danny Mandel wrote:

> Hi all.  I'm wondering if anyone currently has any sort of caching 
> systems in place to cache output for particular components given 
> particular inputs.  Ideally I would like my completed component to 
> function something like this:
>
> <span jwcid="@Conditional" condition="ognl:ifCachedOutputExists">
>    // Insert the cached content here
> </span>
> <span jwcid="@Conditional" condition="ognl:!ifCachedOutputExists">
>    // Perform some expensive calculations and db fetches and at the 
> end of this computation
>    // insert the ouput of this conditional into some cache
> </span>
>
> I guess I have 2 main questions:
> 1) Is there a particular hook in the page/component render cycle that 
> would be an appropriate place to insert this cache insert logic?
> 2) If such a hook exists, is there a way for a component to be aware 
> of the html it has just rendered?
>
> Thanks,
> Danny
>
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> To unsubscribe, e-mail: tapestry-user-unsubscribe@jakarta.apache.org
> For additional commands, e-mail: tapestry-user-help@jakarta.apache.org
>
>



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