About View Object Attributes

View object attributes (view attributes, for short) are named properties that describe the values that rows of a view object might hold, such as:

The Java type of the attribute
The mapping (if any) between the attribute and the query
The mapping (if any) between the attribute and an entity attribute

View attribute settings, with the exception of dynamic view attributes (see below) are stored in the entity object's XML file.

Persistent View Attributes

Persistent view attributes are view attributes which map to a persistent entity attribute. In a particular view row, persistent view attributes will never store values directly. Instead, they store pointers to values in the entity cache.

Persistent attributes are the only ones that you can use to update the datasource. Even if a view attribute is to be read-only, however, there may be advantages to making it persistent, because it allows you to take advantage of Oracle ADF entity caching, which can aid in maintaining a consistent view and may save memory. For more information, see the related topics list.

Entity-Derived View Attributes

Entity-derived view attributes are view attributes which map to a transient entity attribute. In a particular view row, entity-derived view attributes (like persistent view attributes) will never store values directly. Instead, they store pointers to values in the entity cache.

Like persistent view attributes, entity-derived view attributes take advantage of Oracle ADF entity caching, which can aid in maintaining a consistent view and may save memory.

Unlike persistent view attributes, however, entity-derived view attributes (because they are mapped to transient entity attributes) cannot be used to update the datasource. These attributes are best used for temporary calculation and storage. Entity-derived attributes, unlike persistent attributes, can derive their values from complex SQL expressions, or use no SQL at all in their calculations. For more information, see the related topics list.

Transient View Attributes

Transient view attributes are view attributes which are not mapped to an entity attribute at all. In a particular view row, transient view attributes directly store values, rather than storing pointers to the entity cache.

You cannot use transient view attributes to update the datasource. If a view attribute is to be read-only, however, making it transient may have some performance advantages, because it bypasses Oracle ADF entity caching. For more information, see the related topics list.

Transient view attributes, like entity-derived attributes, can derive their values from complex SQL expressions, or use no SQL at all in their calculations. For more information, see the related topics list.

Dynamic View Attributes

Most view attributes are part of the view object definition. However, at runtime, you can also add transient view attributes to a particular view object instance. These view attributes, called dynamic view attributes, will not affect other instances of the same view object.

Dynamic view attributes are always transient.