There are several alternatives here. Why save the entire row?
Typically I see (and do) the saving of id's instead of the entire row. Then subsequent calls use the id for the lookup. Caching can help the performance of the trip to the database... although thats kinda what your problem is here (not enough memory)....
Paging (your google previous, next) is typically done using only the records you display and perhaps the *next* and *previous* records and the number span you are viewing. a good example of paging can be found in suns petstore sample application (http://java.sun.com/blueprints/code/)
A good look over that should save you lots of pain.
regards, Lloyd
Andrew Latham wrote:
I hope someone can assist here.
Basically I have been writing a 3 Tier Web app using Tomcat and trying to adhere to the Struts framework. The application connects to an existing MSSQL database and creates graphs of the data. The way I've built it is I define an entity bean to store a row of returned data from the select query. Each entity bean is appended to a Collection and then made available to the JSP for me to access using <logic:iterate>. This all works fine, until the Collection.size() reaches numbers like 600,000 and then I hit memory issues. I know there is not much I can do but increase -Xmx and page it or buy more physical memory.
The question I have relates to displaying the data. Some of the output I want in a table. Showing all results returned is not good if its more than 100, so I created a "google" type <<previous 10, next 10>> to cycle through them, so for this to happen I need the Collection of what can be 100,000 beans to sit in memory as having to go back and get the next 10 from the SQL database is about 2 minutes each time. When the Collection is returned it has a scope of "Request". To make this available to another JSP page (for the next 10) I rescoped the Collection to "session". This introduces a memory problem where it sits around until the session ends and the GC picks it up. Is there a better way to pass the Collection from one JSP to another without re-scoping it or what I can see happen is that if a user runs many queries they all sit around until the session ends utilising memory.
I've thought I've setting the Collection to NULL when a new query is run. Is this an acceptable method?
Appreciate any advice
Thanks
Andrew Latham
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