25 Using Parameters in Task Flows

This chapter describes how to configure parameters in view activities and in ADF bounded task flows that you create in the Fusion web application. Using these capabilities allows you to manipulate data in task flows, share data between task flows across one or more transactions, and configure return values to return from one task flow to another task flow.

This chapter includes the following sections:

25.1 About Using Parameters in Task Flows

A task flow´s ability to accept input parameters and return parameter values allow you to manipulate data in task flows and share data between task flows. Using these abilities, you can optimize the reuse of task flows in your Fusion web application.

You can use view activity input page parameters as aliases. The alias allows you to map bounded task flow input parameters to page parameters. The view activity input page parameters map managed beans and any information available to the calling task flow to a managed bean on the page itself. To pass values out of view activities, store values in pageFlow scope or managed beans. For information about using view activities in a task flow, see Using View Activities.

For example, a page might specify #{pageFlowScope.empNo} as a page parameter and a bounded task flow might specify #{pageFlowScope.employeeID} as the value of an input parameter definition.

The from-value on the view activity input page parameter would be #{pageFlowScope.employeeID} and the to-value would be #{pageFlowScope.empNo}. This enables reuse of both the page definition and bounded task flow because you do not have to redefine parameters for every context in which each is used.

Other values contained within the task flow can be mapped to input page parameters, not just bounded task flow input parameter definition values.

25.1.1 Task Flow Parameters Use Cases and Examples

Figure 25-1 shows a task flow that defines an input parameter definition to hold information about a user in a pageFlow scope.

Figure 25-1 Task Flow Defining an Input Parameter

This image is described in the surrounding text

25.1.2 Additional Functionality for Task Flows Using Parameters

You may find it helpful to understand other Oracle ADF features before you configure or use a task flow with parameters. Additionally, you may want to read about what you can do with your configured task flows. Following are links to other functionality that may be of interest.

Data controls can be shared between task flows. For more information about sharing data controls, see Sharing Data Controls Between Task Flows .
A task flow can access a managed bean that is registered with it. For more information about managed beans and task flows, see Using a Managed Bean in a Fusion Web Application.
Bounded task flows can be secured by defining the privileges that are required for someone to use them. For more information, see Enabling ADF Security in a Fusion Web Application.

25.2 Passing Parameters to a View Activity

Figure 25-2 illustrates how to configure an input page parameter mapping. You can pass a parameter to the Employee activity as a pageFlowScope value or a value on a managed bean. You can pass a parameter to the Employee activity using an EL expression or a literal expression. The Employee activity, in turn, can pass a value to the Target activity by specifying the value it wants to pass to the Target activity in the to-value element.

Figure 25-2 Task Flow with Two Activities

25.2.1 How to Pass Parameters to a View Activity

You add one or more input page parameters to the view activity that you want to pass parameters to.

Before you begin:

It may be helpful to have an understanding of the configuration options available to you before you define an input page parameter for a view activity. For more information, see Passing Parameters to a View Activity.

You may also find it helpful to understand functionality that can be added using other task flow features. For more information, see Additional Functionality for Task Flows Using Parameters.

To define an input page parameter for a view activity:

In the Applications window, double-click the task flow that contains the view activity to which you want to pass a parameter.
Select the view activity in the diagram for the task flow and, in the Properties window, expand the Page Parameters category.
In the Input Page Parameters list, click the Add icon and enter values as follows:
- From Value: write an EL expression that, when evaluated, specifies where the view activity retrieves the value for the input page parameter. For example, write an EL expression similar to the following:
  
  #{pageFlowScope.EmployeeID}
  
  You can configure the view activity to retrieve a value that is input to the task flow if you write an EL expression for From Value that corresponds to the value for the input parameter that you defined for the task flow, as described in How to Pass an Input Parameter to a Bounded Task Flow.
- To Value: write an EL expression, that when evaluated, specifies where the page associated with the view activity can retrieve the value of the input page parameter. For example, write an EL expression similar to the following:
  
  #{pageFlowScope.EmployeeNo}

25.2.2 What Happens When You Pass Parameters to a View Activity

JDeveloper writes entries to the source file of the task flow at design time, as illustrated in the following example.

<view id="reducedAccess">
 <page>/secured/Information.jsf</page>
      <input-page-parameter>
        <from-value>#{res['infoUsage.reducedAccess.messageHeader']}</from-value>
        <to-value>#{pageFlowScope.infoPageHeaderText}</to-value>
      </input-page-parameter>
      <input-page-parameter>
        <from-value>#{res['infoUsage.reducedAccess.messageHeader']}</from-value>
        <to-value>#{pageFlowScope.infoPageMsg}</to-value>
      </input-page-parameter>
      <input-page-parameter>
        <from-value>info</from-value>
        <to-value>#{pageFlowScope.infoPageType}</to-value>
      </input-page-parameter>
    </view>

At runtime, the view activity retrieves the value of the input parameter from the location you specified in the <from-value> element. The view activity makes the value of the parameter available to its associated page in the location you specified in the <to-value> element.

25.2.3 What You May Need to Know About Specifying Parameter Values

You can specify parameter values using standard EL expressions if you call a bounded task flow using a task flow call activity or you render the bounded task flow in an ADF region or an ADF dynamic region. For example, you can specify parameters using the following syntax for EL expressions:

#{bindings.bindingId.inputValue}
#{CustomerBean.zipCode}

The following example shows the metadata for a task flow binding that renders in an ADF region.

<taskFlow id="Department1" taskFlowId="/WEB-INF/Department.xml#Department"
              xmlns="http://xmlns.oracle.com/adf/Controller/binding">
    <parameters>
        <parameter id="DepartmentId" value="#{bindings.DepartmentId.inputValue}"
                   xmlns="http://xmlns.oracle.com/adfm/uimodel"/>
     </parameters>
</taskFlow>

Appending inputValue to the EL expression makes sure that you assign the parameter the value of the binding rather than the actual binding object.

25.3 Passing Parameters to a Bounded Task Flow

A called bounded task flow can accept input parameters from the task flow that calls it or from a task flow binding. To pass an input parameter to a bounded task flow, you specify one or more:

Input parameters on the task flow call activity in the calling task flow

Input parameters specify where the calling task flow stores parameter values.
Input parameter definitions on the called bounded task flow

Input parameter definitions specify where the called bounded task flow can retrieve parameter values at runtime.

Specify the same name for the input parameter that you define on the task flow call activity in the calling task flow and the input parameter definition on the called bounded task flow. Do this so you can map input parameter values to the called bounded task flow.

If you do not specify an EL expression to reference the value of the input parameter, the EL expression for value defaults to the following at runtime:

#{pageFlowScope.parmName}

where parmName is the value you entered for the input parameter name.

In an input parameter definition for a called bounded task flow, you can specify an input parameter as required. If the input parameter does not receive a value at runtime or design time, the task flow raises a warning in a log file of the Fusion web application that contains the task flow. An input parameter that you do not specify as required can be ignored during task flow call activity creation.

Task flow call activity input parameters can be passed by reference or passed by value when calling a task flow using a task flow call activity unless you are calling a task flow in an ADF region. If the task flow renders in an ADF region, the task flow call activity passes the input parameters by reference. By default, primitive types (for example, int, long, or boolean) are passed by value (pass-by-value).

The Pass By Value checkbox applies only to objects, not primitives and is used to override the default setting of passing by reference. Mixing the two, however, can lead to unexpected behavior in cases where parameters reference each other. If input parameter A on the task flow call activity is passed by value and if input parameter B on the task flow call activity is passed by reference, and B has a reference to A, the result can be two different instances of A and B.

How to Pass an Input Parameter to a Bounded Task Flow, describes how to pass an input parameter from a calling task flow to a called bounded task flow using a task flow call activity. Although you can pass parameter values from any activity on the calling task flow, the passed parameter in How to Pass an Input Parameter to a Bounded Task Flow contains the value of an input text field on a page in the calling task flow.

If you call a bounded task flow using a URL rather than a task flow call activity, you pass parameters and values on the URL itself. For more information, see How to Call a Bounded Task Flow Using a URL.

Instead of explicitly passing data controls as parameters between task flows, you can simply share them by specifying the data-control-scope option on the called bounded task flow. For more information, see Sharing Data Controls Between Task Flows .

A called task flow can also return values to the task flow that called it when it exits. For more information about returning values from a bounded task flow, see Configuring a Return Value from a Bounded Task Flow.

25.3.1 How to Pass an Input Parameter to a Bounded Task Flow

You define values on the calling task flow and the called task flow.

Before you begin:

It may be helpful to have an understanding of the configuration options available to you before you configure a bounded task flow to receive an input parameter. For more information, see Passing Parameters to a Bounded Task Flow.
You may also find it helpful to understand functionality that can be added using other task flow features. For more information, see Additional Functionality for Task Flows Using Parameters.

You will need to complete these tasks:

Create a calling and called task flow

The calling task flow can be bounded or unbounded. The called task flow must be bounded. For more information about creating task flows, see Creating a Task Flow.
Add a task flow call activity to the calling task flow

Figure 25-3 shows an example where the view activity passes control to the task flow call activity.

Figure 25-3 Calling Task Flow

To pass an input parameter to a bounded task flow:

In the Applications window, double-click the JSF page that contains an input component where an end user enters a value that gets passed to a bounded task flow as a parameter at runtime.

The JSF page that you open should be referenced by a view activity in the calling task flow.
Select an input text component on the JSF page where an end user enters a value at runtime.
In the Properties window, expand the Common section and enter a value for the input text component in the Value field.

You can specify the value as an EL expression, for example #{pageFlowScope.inputValue}.
In the Applications window, double-click the task flow that is going to be called.
In the editor window, click the Overview tab.
In the overview editor, click the Parameters navigation tab and then click the Add icon to define a new entry in the Input Parameter Definition section.
In the Name field, enter a name for the parameter, for example, inputParm1.
In the Value field, enter an EL expression where the parameter value is stored and referenced, for example, #{pageFlowScope.inputValue}.
In the Applications window, double-click the calling task flow that contains the task flow call activity to invoke the called bounded task flow.
In the Applications window, drag the called bounded task flow and drop it on top of the task flow call activity that is located in the diagram of the calling task flow.

Dropping a bounded task flow on top of a task flow call activity in a diagram automatically creates a task flow reference to the bounded task flow. As shown in Figure 25-4, the task flow reference contains the bounded task flow ID and a document name. The bounded task flow ID (id) is an attribute of the bounded task flow's <task-flow-definition> element. The document name points to the source file for the task flow that contains the ID.

Figure 25-4 Task Flow Reference
In the Properties window for the task flow call activity, expand the Parameters section to view the Input Parameters section.
Enter a name that identifies the input parameter.

Because you dropped the bounded task flow on a task flow call activity having defined input parameters, the name should already be specified. You must keep the same input parameter name.
Enter a parameter value, for example, #{pageFlowScope.parm1}.

The value on the task flow call activity input parameter specifies where the calling task flow stores parameter values.

The value on the input parameter definition for the called task flow specifies where the value will be retrieved from for use within the called bounded task flow once it is passed.
At runtime, the called task flow is able to use the input parameter. Since you specified pageFlowScope as the value in the input parameter definition for the called task flow, you can use the parameter value anywhere in the called bounded task flow. For example, you can pass it to a view activity on the called bounded task flow. For more information, see What Happens When You Pass Control Between View Activities.

25.3.2 What Happens When You Pass an Input Parameter to a Bounded Task Flow

JDeveloper writes entries to the source files for the calling task flow and called task flow based on the values that you select. Example 25-1 shows an input parameter definition specified on a a bounded task flow.

Example 25-2 shows the input parameter metadata for the task flow call activity that calls the bounded task flow shown in Example 25-1. At runtime, the task flow call activity calls the bounded task flow and passes it the value specified by its value element.

Example 25-1 Input Parameter Definition

<task-flow-definition id="sourceTaskflow">
...
   <input-parameter-definition>
      <name>inputParameter1</name>
      <value>#{pageFlowScope.parmValue1}</value>
      <class>java.lang.String</class>
   </input-parameter-definition>
...
</task-flow-definition>

Example 25-2 Input Parameter on Task Flow Call Activity

<task-flow-call id="taskFlowCall1">
...
    <input-parameter>
      <name>inputParameter1</name>
      <value>#{pageFlowScope.newCustomer}</value>
      <pass-by-value/>
    </input-parameter> 
... 
</task-flow-call>

25.4 Configuring a Return Value from a Bounded Task Flow

You can configure a bounded task flow to return a parameter value to the task flow that calls it. The value that the bounded task flow returns is in addition to the outcome that it returns to the caller when the bounded task flow invokes a task flow return activity, as described in Using Task Flow Return Activities . To return a value, you must configure:

Return value definitions on the called bounded task flow

The return value definition specifies where you store the value that you want to return from the called bounded task flow.
Return values on the task flow call activity in the calling task flow to identify where the calling task flow can find the returned value

You can configure the calling task flow to ignore return value definition from the called task flow by not identifying any return values on the task flow call activity in the calling task flow.

The task flow call activity returns values by reference. For this reason, you do not need to make a copy of the values that you want to return to the calling task flow.

25.4.1 How to Configure a Return Value from a Bounded Task Flow

You configure a return value definition on the called task flow and add a parameter to the task flow call activity in the calling task flow that retrieves the return value at runtime.

Before you begin:

It may be helpful to have an understanding of the interaction between the calling task flow and the called task flow. For more information, see Configuring a Return Value from a Bounded Task Flow.

You may also find it helpful to understand functionality that can be added using other task flow features and parameters. For more information, see Additional Functionality for Task Flows Using Parameters.

You will need to complete this task:

Create a bounded or unbounded task flow (calling task flow) and a bounded task flow (called task flow). For more information, see Creating a Task Flow.

To configure a return value from a called bounded task flow:

In the Applications window, double-click the called task flow.
In the editor window, click the Overview tab.
In the overview editor, click the Parameters navigation tab.
In the Parameters page, click the Add icon for the Return Value Definitions section and add values as follows to define a return value:
- Name: Enter a name to identify the return value. For example, returnValue1.
- Class: Enter a Java class that defines the data type of the return value. The default value is java.lang.String.
- Value: Enter an EL expression that specifies where to read the return value from. For example, enter an EL expression similar to the following:
  
  #{pageFlowScope.ReturnValueDefinition}
In the Applications window, double-click the calling task flow.
In the ADF Task Flow page of the Components window, from the Components panel, in the Activities group, drag and drop a task call activity onto the diagram.
In the Properties window for the task flow activity, expand the Parameters section, click the Add icon next to the Return Values entry and add values as follows to define a return value:
- Name: Enter a name to identify the return value. For example, returnValue1.
  
  The value you enter must match the value you entered for the Name field when you defined the return value definition in Step 4.
- Value: Enter an EL expression that specifies where to store the return value. For example, enter an EL expression similar to the following:
  
  #{pageFlowScope.ReturnValueDefinition}
  
  The value you enter must match the value you entered for the Value field when you defined the return value definition in Step 4.

25.4.2 What Happens When You Configure a Return Value from a Bounded Task Flow

At design time, JDeveloper writes entries to the source files for the task flows that you configured. The following example shows an entry that JDeveloper writes to the source file for the calling task flow.

<task-flow-call id="taskFlowCall1">
      <return-value id="__3">
        <name id="__4">returnValue1</name>
        <value id="__2">#{pageFlowScope.ReturnValueDefinition}</value>
      </return-value>
    </task-flow-call>

The following example shows entries that JDeveloper writes to the source file for the called task flow.

<return-value-definition id="__2">
      <name id="__3">returnValue1</name>
      <value>#{pageFlowScope.ReturnValueDefinition}/</value>
      <class>java.lang.String</class>
 </return-value-definition>

At runtime, the called task flow returns a value. If configured to do so, the task flow call activity in the calling task flow retrieves this value.