Consider this scenario (which I came across). You have extended psdi.app.workorder.WO out of the box MBO class with your own cust.app.workorder.WO class to implement you own business logic for work orders. After a while you install the Maximo Scheduler extension and you soon discover that all your custom logic has gone because the WORKORDER object handler in Database Configuration is now psdi.skd.app.workorder.SKDWOSet instead of your custom cust.app.workorder.WOSet class. This is because the Maximo Scheduler installation has overwritten your custom handler.
Lesson learned: If you have custom classes and extend the same classes which other products also are extending, then those classes will get overwritten when other products are installed and your customizations will be lost.
In order to maintain the customizations, you must define a_customer.xml file in the applications\maximo\properties\product folder. The following example shows a sample a_customer.xml file.
<?xml version="1.0" encoding="UTF-8" ?>
<name>My custom classes</name>
<mbo objectname='WORKORDER' extends='psdi.app.workorder.WO'>custom.app.workorder.WO</mbo>
<mboset objectname='WORKORDER' extends='psdi.app.workorder.WOSet'>custom.app.workorder.WOSet</mboset>
Also, you need to create a directory called “a_customer” inside your tools\maximo\en directory. This directory can be left empty.
This will tell the Maximo installer to merge your custom code with the add-ons code.
For more details refer to the following articles:
- Preventing lost customizations when add-on products are installed
- Avoiding message “a_customer.xml file does not exist” on install