Even though the topic sounds very boring, every CQ and Sling developer was at least once faced with the Question: "Is your solution supporting transactions?" Most engineers are familiar with the theory and usage of transaction working in a old fashion J2EE environment. When transitioning to a modern REST application framework like Sling, we are facing many challenges. In most casesthe solution is to use hibernate or similar tools and to leave the RESTful world. In this Session we will talk about transactions in general, explain the different kind of transactions and especially how to deal with services layers in conjunctions with Apache Sling. Various approaches, to help J2EE developers to transition fully to a RESTful world, will be explained.

1. APACHE SLING & FRIENDS TECH MEETUP
BERLIN, 23-25 SEPTEMBER 2013
“RESTful transactions” with Apache Sling
Şenol Taş

2. About
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§ My Name is Şenol Taş
§ Senior Computer Scientist
§ Adobe in Basel, Switzerland
@thelabertasch

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Why such a boring Topic?

4. Because websites are…
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§ No longer simple advertisement
platforms
§ Not only “online Business cards”
§ Not a “nice to have” medium
§ Not a “Playground”
§ …..

5. Because websites are…
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§ Serious business
§ Make $$$
§ Complex
§ MUST have
§ “Real” Applications

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Your Website IS THE Application

7. Let’s….
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§ Find out “what is a transaction?”
§ Quick reminder about REST
§ How do this two concepts work
together?

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What are Transactions?

9. What are Transactions?
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“An input message to a computer system
that must be dealt with
as a single unit of work”

11. What are Transactions?
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§ begin transaction
§ debit checking account
§ credit savings account
§ update history log
§ commit transaction

12. What are Transactions?
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§ Late 70s: Jim Gray defined the
semantic of reliable transactions
§ Early 80s: Andreas Reuter and Theo
Härder defined the acronym “ACID” in
their paper “Principles of Transaction-
Oriented Database Recovery”

13. ACID
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§ Atomicity
§ Consistency
§ Isolation
§ Durability

14. How do tools like hybernate help?
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What is REST?

16. What is REST?
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§ Representational State Transfer
§ Stateless
§ Client-server
§ Cachable
§ Scalable
§ …..

17. What is REST?
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§ So? How does this work together with
transactions?

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REST and transaction is a oxymoron

19. REST and transactions
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§ Atomicity
§ Consistency
§ Isolation
§ Durability

20. What are the challenges?
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§ HTTP REQUEST – RESPONSE
PATTERN
§ STATELESS
§ …..?

21. Change your mindset…
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§ Not everything has to be done in one
request
§ If you are using POST.jsp or similar in
Sling, most likely something is wrong
§ Events and Observations are your
friends
§ Use the full power of the Sling Default
Post and GET Servlet

22. Remember the cheat sheet from Lars?
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23. Example
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§ Resource: /home/senol/profile
§ Begin transaction
§ change interests
§ Commit transaction

24. Begin Transaction
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§ Copy the node /home/senol/profile to
/home/senol/transactions/profile/*

25. Change interests
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§ Update with regular post request

26. Commit transaction
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§ With observation or events
§ Directly

27. Things of interest
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§ Communicating with services layer
§ Distributed transactions
§ Nested transactions
§ Locking…
§ Using Adobe CQ?
§ Have a look at the Workflow Launcher!

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Thank you and have a RESTful Day!