Oracle Internet File System Developer's Guide
Release 1.1

Part Number A75172-04






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Using Overrides

This chapter covers the following topics:

What Is an Override?

Overrides belong to the category of Oracle Internet File System customization, which includes:

Of these four types of customization, overrides present a significant leap in complexity. Except for renderers, the other types of customization take place on the client, or "bean-side." These more common types of customization use the extensive classes found in the oracle.ifs.beans package. With overrides, we tackle "server-side" processing, using a more limited published API.

An override is a method that allows an application program to intervene in a predefined way with the standard repository operations:

Note: For the 1.1 release of Oracle iFS, overrides are applicable only to Insert, Update, and Free operations. No overrides are available for other database operations, such as copy, add item to folder, or remove item from folder. This functionality is planned for future releases of the product.

How Pre- Overrides Work

The Pre- overrides work by allowing you to interrupt the standard flow of processing on the server side at certain predefined points. At these points, you can specify custom processing to occur before one or more of the standard database operations takes place. For example, your custom validation routine might be incorporated into both PreInsert and PreUpdate overrides.

Using Pre- Overrides

The behavior of the actual Insert, Update, and Free operations is complex, and to override the actual operations risks producing unintended and unwanted results.

However, in almost every circumstance, application requirements can be met quite safely by using Pre- methods to interact with the repository immediately before the specified operation. Because the Pre- overrides are the most frequently used, the balance of this chapter focuses on Pre- overrides.

The following table presents an example of how each override method might be used.

Operation  Override Method  Usage Example 



To add a certain attribute with a specified value to every new instance of a custom document class. 



Same as for Insert, to extend this processing to Update operations. Or to provide special validation on Update. 



To write a copy to a Deletions log file. 

Before You Begin Working with Overrides

Because working with overrides is a complex task, we recommend that you postpone tackling overrides until you have had considerable experience with Oracle iFS and its Java API. Specifically, we suggest that your background should include knowledge and hands-on experience in the following areas:

Providing this range of information is beyond the scope of this Guide. To gain the experience required to tackle overrides, we suggest beginning with several less-complex Oracle iFS applications. This hands-on experience, combined with attendance at Oracle iFS training, will provide the needed familiarity with the Oracle iFS objects and the way they work together.

Review of Attributes

If you have created Oracle iFS objects using the classes of the Oracle iFS API, you will recall the two-phase method of object creation:

  1. Create a Definition object.

  2. Pass the Definition object to the method that actually creates the object.

For example, for a document, you would first create a DocumentDefinition object, then pass that object as an argument to the LibrarySession.createPublicObject() method. For more information, see "Creating a New Document" in Chapter 3, "Working with Documents".

Attributes and Server-Side Classes

In the Oracle iFS Java class hierarchy each Oracle iFS object has two representations:

When you work with overrides, you are working with objects in the Oracle iFS repository. In this context, you use the S_ classes, such as S_Document, rather than the familiar bean-side classes, such as Document.

Attributes and Special Options

The function of the Definition object is to specify the object's attributes. When you create a DocumentDefinition object, you set two types of information:

User-set Attributes and Derived Attributes

Attributes can also be divided into two categories based on their origin:

Override Methods

The override methods provide pre-processing for the standard database operations:

Because overrides by their nature take place on the server-side, all the override methods are located in the S_LibraryObject class and its subclasses. Just as oracle.ifs.beans.LibraryObject provides a bean-side Java representation for all the objects that end users manipulate directly (such as documents and folders), oracle.ifs.server.S_LibraryObject provides the server-side Java representation for these same objects.

Operation  Method  Purpose 






Performs designated operations before inserting an iFS object into the database. For example, used to modify any attributes after the Definition object has been created but before the Insert takes place. 






Performs designated operations before updating an iFS object in the database.  






Performs designated operations before freeing a database object. Note that this method is overridden by classes that need to perform operations before successfully deleting the rows for the freed instance. 

Writing an Override

To plan an override, first decide which operation or operations you want to override (Insert, Update, or Free).

To write an override, follow these steps:

  1. Declare the Server-side Class.

  2. Create the Constructor.

  3. Implement the Override Method.

Declare the Server-side Class

Assume you have already created a bean-side custom class called PurchaseOrder that extends the Document class. Now you decide you want to add some special validation checks via a PreInsert override.

First you create a server-side Java class, S_PurchaseOrder, to represent your custom class in the server. S_PurchaseOrder extends S_TieDocument. Tie classes allow you to "tie" into the class hierarchy at any level, letting you customize without changing the way the class hierarchy is structured. For more information, see "Tie Classes" in Chapter 2, "API Overview".

Put this class into a new custom package, such as MyCompany.MyApp.server.
(Do not add this class to the oracle.ifs.server package).

Sample Code: Declare the Class

public class S_PurchaseOrder extends S_TieDocument

Create the Constructor

Every override class must implement two constructors:

Sample Code: Constructor

public S_PurchaseOrder(S_LibrarySession session, S_LibraryObjectData data)
throws IfsException

Parameters  Datatype  Description 



Current LibrarySession. 



Data component 

Sample Code: Constructor

public S_PurchaseOrder(S_LibrarySession session, java.lang.Long classID)
throws IfsException

Parameters  Datatype  Description 



Current LibrarySession. 



Class ID for the object that is in the process of being created. 

Implement the Override Method

The S_PublicObject class provides Pre- methods for the standard database operations. For a complete list, see "Override Methods".

The following table describes the parameters of the Override methods.

Parameter  Datatype  Description 



Used by the system to track the current state of operations. 



Current object definition to be updated with system attributes. 

Sample Code: Implement the Override Method

public void extendedPreInsert(OperationState opState, 
S_LibraryObjectDefinition def) throws IfsException { super.extendedPreInsert(opState, def); //Add your validation code here. }

The first call after the method begins should be to "super." This call implements processing from the superclass of this object. In this case, it allows both the
S_Document class and the S_PublicObject class to perform processing.

After that, add any specific validation code that your application requires. For example, in the custom bean-side class for Purchase Order, you may have added a setApprover() method. Before you insert the PurchaseOrder object into the database, you may want to check the value of that Approver, and perform one of the following actions:

Sample Code: A PreInsert Override

The following sample code provides a brief example of using a PreInsert override to add server-side validation. Note the following three lines shown in bold, where placeholders are used that must be replaced with appropriate code for your application:

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