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Got two books on Google App Engine for Java

Posted on 28. Dec, 2009 by Tahir Akram.

Recently I got two books on Google App Engine for Java. Programming Google App Engine by Oreilly and Beginning Google App Engine by Apress. There is less material and comprehensive online tutorials available on this. So its better that you read book on it. I started reading Oreilly’s book. I completed some of the basic [...]

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Spoken on Google App Engine at a conference in UET

Posted on 19. Dec, 2009 by Tahir Akram.

Today I had delivered a workshop on Developing Java Web Applications In Google App Engine. This workshop was the part of events of 3rd International Conference on Open Source Systems and Technologies. It was organized by Al-Khawarizmi Institute of Computer Science , University of Engineering and Technology, Lahore.
I have presented following slides there. Also coded [...]

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Tutorial: JPA on Google App Engine

Posted on 13. Dec, 2009 by Tahir Akram.

This project will create and delete an entity record. I have chosen JPA for datastore in app engine. You can also look JDO for this purpose. But my choice to go for JPA is due to Sun standardization on it.
I am using App Engine SDK version 1.2.18
Project name: engineplay
URL: http://engineplay.appspot.com
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Project structure:
UserPrefs.java: The entity class

package com.engineplay.datastore.pojos;
import [...]

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Upgrading to Google App Engine Java SDK 1.2.8

Posted on 07. Dec, 2009 by Tahir Akram.

I was getting following exception while trying to code my first interaction with JPA in Google App Engine.
org.datanucleus.metadata.InvalidMetaDataException:
Error in MetaData for field "user" in class "com.engineplay.datastore.pojos.UserPrefs" : this is declared as com.google.appengine.api.users.User with "persistence-modifier=none" yet has either "default-fetch-group=true" or "primary-key=true" specified! These should be false.
After some searching I came to know that I should upgrade [...]

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Determine whether application is running on local server or App Engine

Posted on 01. Dec, 2009 by Tahir Akram.

If you are working on developing some application on Google App Engine. You may come up with such situation to switch your production code with your local dev code. Following is my solution for this problem. I have initialized a servlet from web.xml. That set appropriate value in a static boolean. I will use this [...]

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How to avoid DeadlineExceededException in Google App Engine

Posted on 03. Oct, 2009 by Tahir Akram.

If you are developing web application on Google App Engine for Java. And you dont know what this exception is. You can be in trouble. The container throws this exception for those requests which take time more than 30 seconds. In other words GAE wants every requests to be fullfilled within 30 seconds.
Case
I am developing [...]

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SCJP Plus Beta Certification exam delayed

Posted on 28. Aug, 2009 by Tahir Akram.

When I came to know that Sun is giving away the opportunity to sign up for newly launched SCJP i.e. Sun Java Programmer Plus certification. I registered for it. According to them Selected candidates will be given the opportunity to appear in beta test for free. But still they have this announcement on their website.
And [...]

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HashMap vs Hashtable vs HashSet

Posted on 24. Aug, 2009 by Tahir Akram.

I was reading about collection framework of Java. And was studying Hashtable, HashMap and HashSet. Its quite interesting to know the differences between them. In this post I will discuss these three with examples.
Hashtable
Hashtable is basically a datastructure to retain values of key-value pair.

It didn’t allow null for both key and value. You will get [...]

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Sun has announced Java Store

Posted on 04. Jun, 2009 by Tahir Akram.

Sun Microsystems has unleashed Java Store at store.java.com. The purpose of this store is to give opportunities to developers to make money by showcasing their Java applications. Which they care about and develop in their own time. Currently store is in beta and available for US residents only.
Sun chief executive Jonathan Schwartz and Java creator [...]

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Sun should promote its Java forum contributors

Posted on 12. May, 2009 by Tahir Akram.

SUN Forums are ultimate source to get help about programming problems and support about Java platform. Its the largest community driven by Java developers. If you are a Java developer then you must have used these forums. You guys will be aware of Duke dollar. You assign duke dollars to your topic (to attract others [...]

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