Oracle ADF Architecture TV - Design - Task Flow Data Control Scope Options

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Task Flow Data Control Scope Options

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Real World ADF Design & Architecture Principles

15th Feb 2013 v1.0


Learning Objectives

•  At the end of this module you should be able to:

– Understand how the traditional concept of transactions aligns to that of ADF

–  Identify different data controls and their transaction capabilities – Explain the influence of the task flow data control scope option

and how it relates to data controls

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Program Agenda

•  Transactions Revisited •  ADF Data Controls •  Task Flow “Data Control Scope"

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In terms of database systems what is a transaction? Why are they needed?

In ADF where are the transactional capabilities defined?

Exercise



Transactions Revisited

•  The common definition

– A collection of work with a start and end – Commit or rollback acts on the entire collection of work –  If an errors occur we don’t get stuck half way

– Other users are isolated from the transactions – Only future transactions see the results


Transactions – What You Forgot

•  Remember transactions aren’t just about commit and rollback

–  They allow one user to chain operations together – Not just separate atomic actions – Each operation sees the previous changes within the transaction – Not visible to other users, but are visible to the current user – As such transactions are also a form of state management


Where in ADF are the transactional capabilities

exposed (defined) to the UI layer again?

Exercise



Transactions & Data Controls

•  Data controls provide the transactional APIs in ADF – Remember this isn’t just commit and rollback – But also state management

•  Typically one instance is given to each user session –  This separates users’ transactions

•  Dependent on design – A user can be given multiple instances to perform multiple

transactions


Program Agenda

•  Transactions Recap •  ADF Data Controls •  Task Flow “Data Control Scope"


ADF Data Controls Types

•  ADF BC •  EJB/JPA •  POJO •  RESTful/URL •  SOAP/Web service •  Custom data controls

All designed to carry state

EJB/JPA out-of-the-box uses an implicit commit

model

Only ADF BC supports explicit commit &

rollbacks


ADF Data Controls Challenges •  If transactions are logically mapped to navigating groups of web pages

–  Q: How do we map the data control transaction to these boundaries?

•  If we need to support separate transactions per session –  Q: How do we configure this with just one data control?

•  If ADF libraries may split data control definitions –  Q: How to combine @ runtime with one instance and they can share state?

•  If our application uses multiple different data control types –  Q: How to commit/rollback as a group?


ADF Data Controls Challenges & Solutions •  If transactions are logically mapped to navigating groups of web pages

–  Q: How do we map the data control transaction to these boundaries? –  A: Task flows allow you to define groups of pages/fragments and task flows

•  If we need to support separate transactions per session –  Q: How do we configure this with just one data control? –  A: Task flows can create a new data control or share an existing one

•  If ADF libraries may split data control definitions –  Q: How to combine @ runtime with one instance and they can share state? –  A: Intelligence is built in to combine data controls at runtime

•  If our application uses multiple different data control types –  Q: How to commit/rollback as a group? –  A: Task flows track the data controls attached as a group






•  If our application uses multiple different data controls –  Q: How to commit/rollback as a group? –  A: Task flows track the data controls attached as a group

Answered in the previous presentations







Answered in the this presentation







Answered in the next presentation


Task Flow Transaction and Data Control Scope Options

<?xml version="1.0" encoding="ISO-8859-1" ?> <adfc-config xmlns="http://xmlns.oracle.com/adf/controller" version="1.2"> <task-flow-definition id="task-flow-definition"> <transaction> <new-transaction/> </transaction> <data-control-scope> <isolated/> </data-control-scope> <use-page-fragments/> </task-flow-definition> </adfc-config>


Shared Data Control Scope

•  “Share data controls with calling task flow” •  Shared

–  Between calling & called task flows –  If data controls are of the same

name and type –  Only one instance of the data

control will be created & shared –  And view objects sharing:

• Current row indicators •  Edit the same records • One database connection


Isolated Data Control Scope

•  Don’t’ “Share data controls with calling task flow” •  Isolated

–  Regardless two instances of the data control

–  Allows disparate data control transactions

–  Separate view objects • No record coordination •  Isolated record editing •  Separate connections


Our system provides the user access to two isolated instances of the same data control simultaneously, and we're now infrequently

hitting row lock errors.

Why and what’s the solution?

Exercise



Shared Data Control Scope: To

2

1

3

4


Shared Data Control Scope: Returning

1 3 4

2


Isolated Data Control Scope: To

1

2

4 3


Isolated Data Control Scope: Returning


Isolated Data Control Scope: Returning

1 2

4

5

3 6

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Every isolated task flow means separate data control instances, more memory consumed, and if using ADF BC more database

connections consumed.


Rules for Sharing Data Controls

•  Data control must be in same data control frame •  Same data control type – eg. ADF BC, EJB, WebService •  Across ADF Libraries

– At design time if same data control comes from two different ADF libraries, if they have the same name they can also share


Conclusion

•  The data control scope allows task flows to share or create separate instances of data controls

•  If shared they will share a transaction and state •  If isolated they will have their own transaction and state •  Isolated makes sense when parts of the application state must

be kept separate and independent –  But does have an overhead of extra memory and (for ADF BC) database

connections –  And you lose sharing state (such as current iterator positions) across

separate instances of the same view object


Further Reading

Essential to view the next slides on Task Flow Transaction Options


Technology

Oracle ADF Architecture TV - Design - Task Flow Data Control Scope Options