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G Performing Common Oracle Forms Tasks in Oracle ADF

This appendix describes how common Oracle Forms tasks are implemented in Oracle ADF. In Oracle Forms, you do some tasks in the data block, and others in the UI. For this reason, the appendix is divided into two sections: tasks that relate to data, and tasks that relate to the UI.

This appendix includes the following sections:

G.1 Concepts Familiar to Oracle Forms Developers

ADF Business Components implements all of the data-centric aspects of Oracle Forms runtime functionality, but in a way that is independent of the user interface. Responsibilities between the querying and entity-related functions are cleanly separated, resulting in better reuse, as described in Table G-1.

Table G-1 Concepts for Oracle Forms Developers

This concept Maps to Oracle ADF With these similarities

Headless Form Module

Application Module

The application module component is the "data portion" of the form. The application module is a smart data service containing a data model of master-detail-related queries that your client interface needs to work with. It also provides a transaction and database connection used by the components it contains. It can contain form-level procedures and functions, referred to as service methods, that are encapsulated within the service implementation. You can decide which of these procedures and functions should be private and which ones should be public.

Forms Record Manager

Entity Object

The entity object component implements the "validation and database changes" portion of the data block functionality. In the Forms runtime, this duty is performed by the record manager. The record manager is responsible for keeping track of which of the rows in the data block have changed, for firing the block-level and item-level validation triggers when appropriate, and for coordinating the saving of changes to the database. This is exactly what an entity object does for you. The entity object is a component that represents your business domain entity through an underlying database table. The entity object gives you a single place to encapsulate business logic related to validation, defaulting, and database modification behavior for that business object.

Data Block

View Object

The view object component performs the "data retrieval" portion of the data block functionality. Each view object encapsulates a SQL query, and at runtime each one manages its own query result set. If you connect two or more view objects in master-detail relationships, that coordination is handled automatically. While defining a view object, you can link any of its query columns to underlying entity objects. By capturing this information, the view object and entity object can cooperate automatically for you at runtime to enforce your domain business logic, regardless of the "shape" of the business data required by the user's task.


G.2 Performing Tasks Related to Data

In Oracle Forms, tasks that relate solely to data are performed in the data block. In Oracle ADF, these tasks are done on the business components that persist data (entity objects) and on the objects that query data (view objects).

G.2.1 How to Retrieve Lookup Display Values for Foreign Keys

In Oracle Forms, an editable table often has foreign key lookup columns to other tables. The user-friendly display values corresponding to the foreign key column values exist in related tables. You often need to present these related display values to the user.

In Oracle Forms, this was a complicated task that required adding nondatabase items to the data block, adding a block-level POST-QUERY trigger to the data block, and writing a SQL select statement for each foreign key attribute. Additionally, if the user changed the data, you needed to sync the foreign key values with an item-level WHEN-VALIDATE-ITEM trigger. This process is much easier in Oracle ADF.

Implementation of the task in Oracle ADF

  1. Create a view object that includes the following:

    • The main, editable entity object as the primary entity usage

    • Secondary "reference" entity usages for the one or more associated entities whose underlying tables contain the display text

    For more information, see Section 5.6.1, "How to Create Joins for Entity-Based View Objects."

  2. Select the desired attributes (at least the display text) from the secondary entity usages as described in Section 5.6.3, "How to Select Additional Attributes from Reference Entity Usages."

    At runtime, the data for the main entity and all related lookup display fields is retrieved from the database in a single join.

    If the user can change the data, no additional steps are required. If the user changes the value of a foreign key attribute, the reference information is automatically retrieved for the new, related row in the associated table.

G.2.2 How to Get the Sysdate from the Database

In Oracle Forms, when you wanted to get the current date and time, you retrieved the sysdate from the database. In Oracle ADF, you also have the option of getting the system date using a Java method or a Groovy expression.

Implementation of the task in Oracle ADF

To get the system date from the database, you can use the following Groovy expression at the entity level:

DBTransaction.currentDbTime

Note:

The DBTransaction reference is for entity-level Groovy expressions only.

If you want to assign a default value to an attribute using this Groovy expression, see Section 4.10.7, "How to Define a Default Value Using an Expression."

To get the system date from Java, you call the getCurrentDate() method. For more information, see Section 12.10, "Accessing the Current Date and Time."

G.2.3 How to Implement an Isolation Mode That Is Not Read Consistent

In Oracle Forms, you might have been concerned with read consistency, that is, the ability of the database to deliver the state of the data at the time the SQL statement was issued.

Implementation of the task in Oracle ADF

If you use an entity-based view object, the query sees the changes currently in progress by the current user's session in the pending transaction. This is the default behavior, and the most accurate.

If instead, you want a snapshot of the data on the database without considering the pending changes made by the current user, you can use a read-only view object and reexecute the query to see the latest committed database values. For more information on read-only view objects, see Section 5.8.1, "How to Create an Expert Mode View Object."

G.2.4 How to Implement Calculated Fields

Calculated fields are often used to show the sum of two values, but they could also be used for the concatenated value of two or more fields, or the result of a method call.

Implementation of the task in Oracle ADF

Calculated attributes are usually not stored in the database, as their values can easily be obtained programmatically. Attributes that are used in the middle tier, but that are not stored in the database are called transient attributes. Transient attributes can be defined at the entity object level or the view object level.

If a transient attribute will be used by more than one view object that might be based on an entity object, then define the attribute at the entity object level. Otherwise, define the transient attribute at the view object level for a particular view object.

To define transient attributes at the entity object level, see Section 4.11, "Adding Transient and Calculated Attributes to an Entity Object." To define transient attributes at the view object level, see Section 5.4, "Adding Calculated and Transient Attributes to a View Object."

G.2.5 How to Implement Mirrored Items

In Oracle Forms, you may be used to using mirrored items to show two or more fields that share identical values.

Implementation of the task in Oracle ADF

There is no need to have mirrored items in Oracle ADF, because the UI and data are separated. The same view object can appear on any number of pages, so you don't need to create mirrored items that have the same value. Likewise, a form could have the same field represented in more than one place and it would not have to be mirrored.

G.2.6 How to Use Database Columns of Type CLOB or BLOB

If you are used to working with standard database types, you may be wondering how to use the CLOB and BLOB types in Oracle ADF.

Implementation of the task in Oracle ADF

In Oracle ADF, use the built-in data types ClobDomain or BlobDomain. These are automatically created when you reverse-engineer entity objects or view objects from existing tables with these column types. ADF Business Components also supports data types for Intermedia column types: OrdImage, OrdAudio, OrdDoc, and OrdVideo. For more information, see Section 4.10.1, "How to Set Database and Java Data Types for an Entity Object Attribute."

G.3 Performing Tasks Related to the User Interface

In Oracle ADF, common UI-related tasks (such as master-detail screens, popup list of values, and page layout) are handled quite differently than they were in Oracle Forms.

G.3.1 How to Lay Out a Page

Oracle Forms is based on an absolute pixel or point-based layout, as compared to the container-based approach of JSF, and the Layout Manager approach in ADF Swing.

Implementation of the task in Oracle ADF

See Developing Web User Interfaces with Oracle ADF Faces for information on how to lay out a page in Oracle ADF.

G.3.2 How to Stack Canvases

In Oracle Forms, stacked canvases were often used to hide and display areas of the screen.

Implementation of the task in Oracle ADF

The analog of stacked canvases in Oracle ADF is panels (layout containers) with the rendered property set to true or false. See Developing Web User Interfaces with Oracle ADF Faces for more information.

G.3.3 How to Implement a Master-Detail Screen

Master-detail relationships in Oracle ADF are coordinated through a view link. A view link is conceptually similar to an Oracle Forms relation.

Implementation of the task in Oracle ADF

For information on how create view links, see Section 6.2, "Working with Multiple Tables in a Master-Detail Hierarchy." Once you have established a relationship between two view objects with a view link, see Section 6.2.4, "How to Enable Active Master-Detail Coordination in the Data Model."

G.3.4 How to Implement an Enter Query Screen

In Oracle Forms, another common task was creating an enter query screen. That is, a screen that starts in Find mode.

Implementation of the task in Oracle ADF

In Oracle ADF, this accomplished with a search form. Complete information on how to create a search form is covered in Chapter 33, "Creating ADF Databound Search Forms." In particular, you may want to look at Section 33.3.1, "How to Set Search Form Properties on the View Criteria."

G.3.5 How to Implement an Updatable Multi-Record Table

In Oracle Forms, you may be used to creating tables where you can edit and insert many records at the same time. This can be slightly more complicated when using a JSF page in Oracle ADF, because the operations to edit an existing record and to create a new record are not the same.

Implementation of the task in Oracle ADF

In Oracle ADF, this is done using an input table. To create an input table, see Section 29.4, "Creating an Input Table."

G.3.6 How to Create a Popup List of Values

In Oracle Forms, it was simple to create a list of values (LOV) object and then associate that object with a field in a declarative manner. This LOV would display a popup window and provide the following capabilities:

  • Selection of modal values

  • Query area at the top of the LOV dialog

  • Display of multiple columns

  • Automatic reduction of LOV contents, possibly based on the contents of the field that launched the LOV

  • Automatic selection of the list value when only one value matches the value in the field when the LOV function is invoked

  • Validation of the field value based on the values cached by the LOV

  • Automatic popup of the LOV if the field contents are not valid

Implementation of the task in Oracle ADF

To implement a popup list in Oracle ADF, you configure one of the view object's attributes to be of LOV type, and select Input Text with List of Values as the style for its UI hint. For a description of how to do this, see Section 5.12, "Working with List of Values (LOV) in View Object Attributes."

G.3.7 How to Implement a Dropdown List as a List of Values

In Oracle Forms, you could create a list of values (LOV) object and then associate that object with a field in a declarative manner. In Oracle ADF, you can implement an LOV (lookup-value) screen with a search item, usable for a lookup field with many possible values.

Implementation of the task in Oracle ADF

To implement a dropdown list in Oracle ADF, you configure one of the view object's attributes to be of LOV type, and select Input Text with List of Values as the style for its UI hint. For a description of how to do this, see Section 5.12, "Working with List of Values (LOV) in View Object Attributes."

G.3.8 How to Implement a Dropdown List with Values from Another Table

In Oracle Forms, you could create a list of values (LOV) object and then associate that object with a field in a declarative manner. In Oracle ADF, you can implement a dropdown list with string values from a different table. These string values populate the field with an id code that is valid input in the table that the screen is based on.

Implementation of the task in Oracle ADF

To implement a dropdown list of this type in Oracle ADF, you configure one of the view object's attributes to be of LOV type, and select Choice List as the style for its UI hint. For a description of how to do this, see Section 5.12, "Working with List of Values (LOV) in View Object Attributes."

G.3.9 How to Implement Immediate Locking

In Oracle ADF, you can lock a record in the database at the first moment it is obvious that the user is going to change a specific record.

Implementation of the task in Oracle ADF

Immediate row locking can be configured in ADF Business Components, although it is not the default and is typically not used in web application scenarios. For web applications, use the default configuration setting jbo.locking.mode=optimistic. For more information, see Section 49.11.1, "How to Confirm That Applications Use Optimistic Locking."

G.3.10 How to Throw an Error When a Record Is Locked

When a record has been locked by a user, it's helpful to throw an error to let other users know that the record is not currently updatable.

Implementation of the task in Oracle ADF

Locking rows and throwing an exception if the row is already locked is built-in ADF Business Components functionality. There are a couple of different ways that you can handle the error message, depending on whether you want a static error message or a custom message with information about the current row.

  • To throw a static message, register a custom message bundle in your data model project to substitute the default RowAlreadyLockedException's error message with something more meaningful or user-friendly.

  • To throw a message that contains information about the row, override the lock() method on the entity object, using a try/catch block to catch the RowAlreadyLocked exception. After you catch the exception, you can throw an error message that might contain more specific information about the current row.