This presentation slides is for SG GTUG 4th meetup on 17 April 2010. In this presentation, I shared my personal experience in using AppEngine (Java) for my mobile application developments. I used SG 4D, one of my most popular Singapore app, as an example. Topics covered including datamining, cron jobs, JDO, Restlet and Gson.

1. GAE for Mobile Apps How i use Google’s App Engine for my mobile apps

2. About Myself Name: Junda (JD) Blog: Just2me.com twitter: @samwize Mobile lead, Hoiio Bio: Codes for iPhone, Android, BlackBerry & J2ME

3. Hoiio, a smarter app to call & SMS

4. My hobby apps.. SG Toto SG 4D SG Pools How iuse App Enginefor my mobile apps SG Blood txeet SG Wireless Flowers

5. Overview of Topics What I want to develop? What backend server to use? How to datamine? How to store & retrieve? How to create API? How to use the API?

6. 1. What I want to develop?

9. Features Get latest results Get past results Analyze numbers A server-client application

10. 2. What backend server to use?

11. Things I have tried.. ✘ Run little server in school ✘ Get a shared webhost ✘ Get a VPS account

12. Google App Engine ✔ App Engine for Java was launched in April 2009 ✔ Scalable ✔ Multiple versions ✔ Easy to deploy ✔ FREE

13. 3. How to datamine?

14. 3. How to datamine? HTML Parser Setup Cron job

15. Code > HTML Parser

16. Code > Setup cron.xml

17. 4. How to store and retrieve?

18. 4. How to store & retrieve? Java Data Objects (JDO) Or Java Persistence API (JPA) A collection of real-world examples

19. Code > Memcache, JDO Query

20. Pitfalls of Datastore pm.close() – changes are only saved when PersistenceManager is closed! You cannot use inequality filters on more than 1 property! Eg. (x > 0 ANDy > 0) is illegal If you use an inequality filter, then that property MUST be sorted before others! Restrictions on queries and unsupported features of JDO and more..

21. 5. How to create API?

22. 5. How to create API? Restlet for GAE Download GAE version Setup Restlet in web.xml Attach the route eg. /4d Create ServerResource, implement @Get represent() and return JSON string

23. Code > Setup Restlet in web.xml

24. Code > Setup Restlet routes

25. Code > Implement a Restlet resource

26. 5. How to create API? API to return JSON format Gson – Converts Java Objects to JSON string, and vice versa

27. Code > Gson

28. 6. How to use the API?

29. 6. How to use the API? HTTP GET from the service URL Use Gson, or other JSON library Display on the client!

32. This is the last slide!