As usual it took much more work than anticipated, especially as I made the 'mistake' to ask two subject experts (Steve Muench and Sandra Muller from the JHeadstart Team) to review the first draft. If I had not done that, the paper could have been published a month ago! But no, I could not help myself, I had to be thorough, I had to be me, and of course they provided me with insights that have had a significant impact on its contents. But all for the better, otherwise some of it already would have been obsolete the minute it hit the street.
"So what?", those of you who have not seen it before, might ask yourself. Well let me try to explain without copying too much of what already is explained in the paper itself.
First of all it is our (Oracle Consulting's) experience that analyzing, and implementing business rules takes a significant part of the total effort of creating the average application. Although being a very productive persistence framework as it is, this still holds true for ADF Business Components (which is part of Oracle's ADF), or ADF BC for short. Moreover, despite all our efforts trying to create the ultimate application, most resources still are being put in maintenance rather than in creating the original. So there is a lot to be gained for business rules in this regard, and that is what the white paper intends to address.
Does the paper present 'the right way' for ADF BC? Well, perhaps there is a better way, I don't know. But it is a good way, as it is consistent and makes use of the best that ADF BC has to offer. And because it is consistent (and well documented) maintenance also becomes easier, as when the developers that created the original application used it (and then ran away like lightning to build the next hip thing), they will not have left behind a maintenance nightmare. At least not what the business rules are concerned.
"So, what's new?", those of you who have sleep with the previous version of the paper under their pillow, might ask yourself.
Let me give you this short list and for the rest of it refer you to the paper itself:
- Capturing business rules using UML class model
Why? Because plenty of people still want to capture requirements (including business rules) before there are tables and entity objects and therefore cannot make use of an ADF Business Components diagram (see also the article UML Rules! I posted some time ago).
- Setting up framework extension classes
Doing so makes introducing generic functionality later on so much easier and therefore is strongly advised in general.
- Deprecated custom authorization in ADF BC
This in particular concerns the horizontal authorization rules (restricting the set of rows of an entity you are allowed to insert, update or delete). The reason to do so is that you probably rather use Virtual Private Database for that.
- 'Other Attribute Rules' dropped
As I discussed in the article How to Pimp ADF BC Exception Handling, there are no compelling arguments anymore for not using built-in validators or method validators, making that the category Other Attributes Rules could be dropped, and we now suggest implementing them using these validators.
- New built-in attribute validators
ADF BC provides the Length, and Regular Expression validators for attributes.
- 'Other Instance Rules' dropped, 'Delete Rules' added
The category Other Instance Rules is dropped for the same reason the Other Attribute Rules category has been dropped. This with the exception of rules that make use of the delete() method, which rules are now in the new category 'Delete Rules'.
- Registered Rules
Using Registered Rules you can create generic method validators you can use for multiple entities. An example is a reoccurring validation of an end date that must be on or after a begin date.
- UniqueKey Validator
Compared with just checking 'Primary Key' for all primary key attributes, this one and only entity-level built-in validator helps to make validation of the primary key predictable and consistent, and also supports providing a user-friendlier error message.
- 'Change History' and 'Cascade Delete' added
These two categories are subcategories of Change Event Rules with DML. When using JAAS/JAZN ADF BC offers built-in support for recording date/user created/updated information, which has been documented in the Change History category. As a result of introducing this category, the 'Derivation' category has been renamed to 'Other Derivation'. Furthermore, ADF BC also supports Cascade Delete by defining an association as being a 'composition'.
- Sending an email using JavaMail API
The previous version of the paper here and there referred to some 'clex' library which was part of the now long-gone Oracle9iAS MVC Framework for J2EE. If you remember that you really are an Oracle veteran! Anyway, the classical example of a 'Change Event Rule without DML' is sending an email when somebody changes something in the database, which example now is based on the JavaMail API
- Message handling
Especially this subject has been revised significantly. Among other things you can specify error message together with the validator, which message will end up in an entity-specific message bundle. By creating custom exceptions you also can use one single message bundle, as I explained in the article How to Pimp ADF BC Exception Handling.