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

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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

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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

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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

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Where in ADF are the transactional capabilities

exposed (defined) to the UI layer again?

Exercise

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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

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Program Agenda

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

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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

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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?

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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

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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 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

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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 controls –  Q: How to commit/rollback as a group? –  A: Task flows track the data controls attached as a group

Answered in the this presentation

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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 controls –  Q: How to commit/rollback as a group? –  A: Task flows track the data controls attached as a group

Answered in the next presentation

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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>

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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

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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

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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

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Shared Data Control Scope: To

2

1

3

4

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Shared Data Control Scope: Returning

1 3 4

2

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Isolated Data Control Scope: To

1

2

4 3

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Isolated Data Control Scope: Returning

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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.

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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

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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

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Further Reading

Essential to view the next slides on Task Flow Transaction Options

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