About the Task Flow

About the Task Flow

By W.ZH, Jan 2009 abstract from Fusion ADF 11g dev guide

Task flow is an important  new concept in the ADF 11g, especially the bounded task flow. So this article is to summarize the bounded taskflow  for the new beginners.

An ADF bounded task flow is used to encapsulate a reusable portion of an application. A bounded task flow is similar to a Java method in that it:

■ Has a single entry point

■ May accept input parameters

■ May generate return values

■ Has its own collection of activities and control flow rules

■ Has its own memory scope and managed bean lifespan (a page flow scope

instance)

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Bounded Task Flow Features

Well-defined boundary

An ADF bounded task flow consists of its own set of private control flow rules, activities, and managed beans. A caller requires no internal knowledge about them. Input parameters can be passed into the bounded task flow, and output parameters can be passed out on exit of the bounded task flow. Data controls can be shared between task flows.

Single point of entry

An ADF bounded task flow has a single point of entry, a default  activity that executes before all other activities in the task flow.

pageFlow memory scope

You can specify pageFlow as the memory scope for passing data between activities within the ADF bounded task flow. pageFlow scope defines a unique storage area for each instance of an ADF bounded task flow. Its lifespan is the ADF bounded task flow, which is longer than request scope and shorter than session scope.

Addressable

You can access an ADF bounded task flow by specifying its unique identifier within the XML source file for the bounded task flow and the file name of the XML source file.

Reuse

You can identify an entire group of activities as a single entity, an ADF bounded task flow, and reuse the bounded task flow
in another application within an ADF region.

You can also reuse an existing bounded task flow simply by calling it. For example, one task flow can call another bounded task flow using a task flow call activity or a URL.

In addition, you can use task flow templates to capture common behaviors for reuse across different ADF bounded task flows.

Parameters and return values

A caller can pass input parameters to an ADF bounded task flow and accept return values from it. In addition, you can share data controls between bounded task flows.

Transaction management

An ADF bounded task flow can represent a transactional unit of work. You can declaratively specify options on the task flow definition that determine whether, when entering the task flow, the task flow creates a new transaction, joins an existing one or is not part of the existing transaction.

Reentry

You can specify options on the task flow definition that determine whether or not the ADF bounded task flow can be reentered. For more information.

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About  the managed bean for bounded task flow

All memory scopes are supported for managed beans in adfc-config.xml. ADF

bounded task flows allow managed bean scopes of application, session, request,

pageFlow, or none.

In order to allow managed bean customizations in an ADF bounded task flow, ensure

the managed bean metadata resides in the task flow definition for the ADF bounded

task flow. Avoid placing managed beans within the faces-config.xml file.

When an ADF bounded task flow executes, faces-config.xml is first checked for

managed bean definitions, then the task flow definition file for the currently executing

task flow is checked. If no match is found in either location and the managed bean is in

session or application scope, adfc-config.xml and other bootstrap XML source

files are checked.

Lookup precedence is based on memory scope. request scope managed beans take

precedence over session scope managed beans.

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About the Page Flow Memory scope

Each ADF bounded and unbounded task flow exists inside a page flow scope that is

independent of the memory scope for all other task flows. Page flow scope is not a

single state like session scope. It defines a unique storage area for each instance of an

ADF bounded task flow. Each instance of the called ADF bounded task flow has its

own state. An ADF bounded task flow may therefore be called recursively.

Page flow scope is recommended as a means for passing data values between activities

within a task flow. Application and session scopes are also allowed within task flow

definition files, but are not recommended. Avoid using application and session scope variables because they can

persist in memory beyond the life of the ADF task flow. This may compromise the encapsulation and reusable aspects of a task flow.

■ Avoid using session scope to pass values from one ADF task flow to another. Better use page flow scope variables within the ADF task flow,

and use parameters to pass values between task flows.

■ Use view scope for variables that are needed only within the current view activity and not across view activities.

■ Use request scope when the scope does not need to persist longer than the current request.

■ Use backing bean scope managed beans in your task flow if there is a possibility that your task flow will appear in two region components on the same page and you would like to isolate region instances.

As a rule, use the narrowest scope that will work.

When one task flow calls another task flow (Could be in another remote application.), the calling task flow cannot access the called task

flow’s page flow scope and vice versa.

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Use the task flow in the JSP page

You can drop its task flow definition from the Application Navigator onto a JSF page:

■ If the bounded task flow contains view activities that are page fragments, it is

added to the JSF page as an ADF region.

(This means all activities of this task flow will happen within this caller’s page.)

■ If the bounded task flow contains view activities that are pages, you have the

option of adding a button or link to the JSF page. When clicked, the button or link

executes the bounded task flow.

(This means when user click this button, browser will guide the user to a new page belong to the page flow.)

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Task flow conversion and refactoring (This is cool.)

You can convert existing activities, JSF page flows, and JSF pages into new ADF

Controller components such as ADF bounded task flows and task flow templates.

You can create a new ADF bounded task flow based on selected pages in a JSF page

flow. Only pages that are part of a flow (that is, those that are linked by JSF navigation

cases) are converted to view activities in the new task flow.

You can convert an existing ADF bounded task flow to an unbounded task flow or

change whether the views it contains are pages or page fragments.

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A task flow =     activities ( Method Call, Router, Task Flow Call, Task Flow Return,

Save Point Restore, URL View, View-JSP or fragment)

+ control flow cases ( Control Flow Case, Wildcard Control Flow Rule )

Task flow call activity before and after listeners are used to identify the start and end

of an ADF bounded task flow. Specifying a listener in the task flow call activity means

that the listener executes on that specific usage of the called task flow definition.

The task flow return activity identifies the point in the application control flow where

an ADF bounded task flow completes and sends control flow back to the caller. You

can use the task flow return activity only within an ADF bounded task flow.

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The ADF bounded task flow can optionally return a value to the calling page when the

modal dialog is dismissed. The return value can be displayed in an input UI

component on the calling page.

The launching command button must specify a return listener. The return listener is a

method binding for a method with one argument, a return event. The return listener

takes the value specified in the returnEvent and sets it on the input component.

The input UI component should accept the return value of the command button by

specifying a backing bean and setting its partialTriggers attribute to the id of the

launching command button (see Using Input Components and Defining Forms in the

Oracle Fusion Middleware Web User Interface Developer’s Guide for Oracle Application

Development Framework for more information). The backing bean containing the return

listener should be registered in adfc-config.xml.

The target bounded task flow in the example contains a single view activity associated

with a page that contains an output text component. The source task flow passes the

value in the input text field as a parameter to the target task flow (for more

information, see Section 15.2, “Passing Parameters to an ADF Bounded Task Flow”).

In addition, the target task flow should specify a return value definition. To return a

value, you must specify:

■ Return value definition on the called bounded task flow. This specifies where the

return value is to be taken from upon exit of the called bounded task flow.

■ Return values on the task flow call activity in the calling task flow. These specify

where the calling task flow can find return values (for more information, see

Section 15.4, “Specifying Return Values”).

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