How can I load a property lazily in JDO (on Google App Engine)?

Posted by luciano on Stack Overflow See other posts from Stack Overflow or by luciano
Published on 2010-02-09T13:11:01Z Indexed on 2010/04/26 9:33 UTC
Read the original article Hit count: 276

Filed under:

jdo

|

google-app-engine

|

java

|

lazy-loading

|

properties

I have this code in one of my @PersistenceCapable classes:

@Persistent
private Blob data;

The Blob can be quite big, so I'd like to load it lazily since most of the times I don't need it. How can I annotate that property to avoid immediate loading? I could create another class that contains the Blob alone and then use a lazy one-to-one, but I'd like to solve this with annotations.

© Stack Overflow or respective owner

Related posts about jdo

Why "import javax.jdo.* "caused error ?

as seen on Stack Overflow - Search for 'Stack Overflow'
I have a class uses the following lines, it works fine in a Google App Engine project: import javax.jdo.annotations.IdGeneratorStrategy; import javax.jdo.annotations.IdentityType; import javax.jdo.annotations.PersistenceCapable; import javax.jdo.annotations.Persistent; import javax.jdo.annotations… >>> More
Problems Mapping a List of Serializable Objets with JDO

as seen on Stack Overflow - Search for 'Stack Overflow'
I have two classes Invoice and InvoiceItem. I would like Invoice to have a List of InvoiceItem Objets. I have red that the list must be of primitive or serializable objects. I have made InvoiceItem Serializable. Invoice.java looks like import java.util.ArrayList; import java.util.Date; import java… >>> More
How to do this GQL query in JDO

as seen on Stack Overflow - Search for 'Stack Overflow'
I have about 50k entities stored in appengine. I am able to look up an individual record via the GQL admin interface with a query like: SELECT * FROM Pet where __key__ = KEY( 'Pet','Fido') But I'm having trouble figuring out how to do a batch version of this via JDO. Right now I have this: … >>> More
GAE/JDO: How to check whether a field in a detached object was loaded

as seen on Stack Overflow - Search for 'Stack Overflow'
My DAO detaches and then caches certain objects, and it may retrieve them with different fetch groups. Depending on which fetch group was used to retrieve the object, certain fields of that object may be available, or not. I would like to be able to test whether a given field on that object was… >>> More
GAE, JDO, count() doesn't work ?

as seen on Stack Overflow - Search for 'Stack Overflow'
On GAE with Spring/JDO after saving 2 entities (in transaction). On calling getById - entities fetched from data storage. On calling getCount() returns "0" and - on calling getAll() - returns empty collection. plz help me ! DAO: @Override public Long getCount() { return ((Integer) getJdoTemplate()… >>> More

Related posts about google-app-engine

unittest import error with virtualenv + google-app-engine-django

as seen on Stack Overflow - Search for 'Stack Overflow'
I'm working with google-app-engine-django + zipped django. Just running "python manage.py test" succeeded without error. But with virtualenv, test was failed with "import unittest error". same error with Django 1.1. - OSX 10.5.6 - google-app-engine-django (r101 via svn) : r100 was failed with launcher… >>> More
Could not import Django settings into Google App Engine

as seen on Stack Overflow - Search for 'Stack Overflow'
Hello all you Google App Engine experts, I have used Django a little before but am new to Google App Engine and am trying to use it's development web server with Django for the first time. I don't know if this is relevent but I previously had Django 1.1 and Python 2.6 on my Windows XP and even… >>> More
How does Google App Engine precompile Java ?

as seen on Stack Overflow - Search for 'Stack Overflow'
App Engine uses a "precompilation" process with the Java bytecode of an app to enhance the performance of the app in the Java runtime environment. Precompiled code functions identically to the original bytecode. Is there any detailed information what this does? >>> More
Creating a session scoped bean in Google App Engine using Spring 2.5

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi, I am trying to create a session bean in spring mvc. I am having the following error message when I run my google app engine server in my local box: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'siteController' defined in ServletContext resource [/WEB-INF/springapp-servlet… >>> More
Google App Engine UI Widgets

as seen on Stack Overflow - Search for 'Stack Overflow'
Are there any UI widgets available to the python side of Google App Engine? I'd like something like the collapsed/expanded views of Google Groups threads. Are these type things limited to the GWT side? >>> More