Re: List loaded twice from DB

Wed, 31 May 2006 09:22:38 -0700

Hi Marcus,

Ok, I start to understand now.

Are you sure that under production settings (with cache turned on) it will re-initialize the property when the page is put back in the pool, and not when it is checked out of the pool?
I understand the thing about "putting a pristine instance of the page back to the pool" so that no data of one user gets carried over to another user, but if the list is loaded when it is returned to the pool it may be outdated by the time the page is used the next time.

Thanks,

MARK


Schulte Marcus wrote: 
do you have caching disabled?
 I suspect the following?
  Tap inits your prop 
   1. whenever your page is built from the spec/template
   2. whenever it's put back into the pool after use.

With caching disabled 1. and 2. will occur in each request-cycle. 
With production settings, 1 *and* 2 will only occur in the first cycle,
subsequent cycles will only have 2.

btw: I don't disable caching anymore since I discoved the invaluable
reset-Service

  
-----Original Message-----
From: Mark [mailto:[EMAIL PROTECTED]]
Sent: Wednesday, May 31, 2006 7:28 AM
To: Tapestry users
Subject: Re: List loaded twice from DB


Hi Ron,

it sounds like this would work, but isn't this just a workaround for 
something that really should not happen this way in the first place?

Thanks,

MARK

Ron Piterman wrote:
    
just an idea: try to implement the 'roomlist' property 
      
yourself, as I 
    
described in my previous postings, instead of letting 
      
tapestry do it.
    
may be this will help.
don't forget to implement a pageDetachListener which sets 
      
the property 
    
to null.
I always had good experience when doing it like this.
Cheers,
Ron


Mark wrote:
      
Hi Ron,

I don't understand what you mean by "instead of doing it on 
finishLoad()". I did not do anything with finishLoad(), I 
        
don't know 
    
why it calls the getList.

Here is my .page file:


<page-specification 

        
class="com.mark_arnold.sample.rbs1.web.tapestry.page.admin.Roo
mListPage"> 
    
   <inject property="administrationService" 
object="spring:rbsRoomAdminService" />
   <inject property="pageService" object="engine-service:page"/>

   <inject property="messageResource" 
object="spring:applicationContext"/>

   <property 
name="roomList">ognl:administrationService.getAllRooms()</property>
   <property name="debug">true</property>
   <property name="room"/>
   <property name="editPageName" 
initial-value="literal:admin/RoomAdminPage"/>
</page-specification>

My Page class extends BasePage, but only overwrites pageAttached() 
(nothing related to the list in here).

MARK


Ron Piterman wrote:
        
use lazy initialization for the list instead of doing it on 
finishLoad() :

public List getXXXList() {
  if (this.xxxList == null )
    this.xxxList = readXXXList();
  return this.xxxList;
}

+

pageDetachListener -> this.xxxList = null.

Cheers,
Ron


Mark wrote:
          
Hi,

I have a simple CRUD scenario with a "ListPage" and a 
            
"ModifyPage".
    
The ListPage gets all records from the DB by calling the method 
"getAllRooms()" of a "RoomAdminService" and lists them 
            
in a table.
    
For some reason the query "select * from rooms" is 
            
executed twice 
    
every time the page is accessed.

getAllRooms() is only referenced once in the .page file 
            
to plug a 
    
page property, the .html file then references that property

I compared the StackTraces of the two calls, they have identical 
tops and bottoms, but differ somwhere in the middle:

       at $RoomListPage_3.finishLoad($RoomListPage_3.java)
       at 

            
org.apache.tapestry.pageload.PageLoader.constructComponent(Pag
eLoader.java:439) 
    
       at 

            
org.apache.tapestry.pageload.PageLoader.loadPage(PageLoader.java:613)
    
       at 
$IPageLoader_10b79e6e7bf.loadPage($IPageLoader_10b79e6e7bf.java)
       at 
$IPageLoader_10b79e6e7c0.loadPage($IPageLoader_10b79e6e7c0.java)
       at 

            
org.apache.tapestry.pageload.PageSource.getPage(PageSource.java:120)
    
       at 
$IPageSource_10b79e6e724.getPage($IPageSource_10b79e6e724.java)
       at 

            
org.apache.tapestry.engine.RequestCycle.loadPage(RequestCycle.
java:268) 
    
       at 

            
org.apache.tapestry.engine.RequestCycle.getPage(RequestCycle.java:251)
    
       at 

            
org.apache.tapestry.engine.RequestCycle.activate(RequestCycle.
java:609) 
    
       at 

            
org.apache.tapestry.engine.PageService.service(PageService.java:66)
    
       at 

            
$IEngineService_10b79e6e7af.service($IEngineService_10b79e6e7af.java)
    
       at 

            
org.apache.tapestry.services.impl.EngineServiceOuterProxy.serv
ice(EngineServiceOuterProxy.java:66) 
    

and

       at $RoomListPage_3.pageDetached($RoomListPage_3.java)
       at 

            
org.apache.tapestry.AbstractPage.firePageDetached(AbstractPage
.java:452) 
    
       at 
org.apache.tapestry.AbstractPage.detach(AbstractPage.java:140)
       at 

            
org.apache.tapestry.pageload.PageSource.releasePage(PageSource
.java:147) 
    
       at 

            
$IPageSource_10b79e6e724.releasePage($IPageSource_10b79e6e724.java)
    
       at 

            
org.apache.tapestry.engine.RequestCycle.cleanup(RequestCycle.java:192)
    
So it seems like the first call comes out of the finishLoad(), 
while the second call is caused by pageDetached() of my ListPage.


Does anybody know why it would access the getAllRooms() twice?

Thanks,

MARK
            
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