How does Compiere implement persistent connections?

Basically, Compiere puts all the table definitions in ad_table and ad_column, which is also called ad.
Therefore, the dynamic management of PO can be achieved through the definition of AD.
However, in order to adapt to the DB independent plan of Compiere CodeThe level enhances the management of Po, which is basically composed of the following class layers: 1, po. java, which is the base class of all pods and implements query, update, and delete operations.
Especially in this class, Compiere wants it to implement trigger-like functions to port trigger code written in the past using a large number of PL/SQL. We can see that beforesave, aftersave, and other functions are used to replace trigger.
2, X _ ***. Java, which can be automatically generated using the generatemodel tool provided by Compiere,
It inherits the Po and is basically equivalent to a simple bean, which is composed of get and set of some classes.
3. Generally, more complex functions are required. Therefore, most tables have a corresponding M ***. Java
It inherits X _ ***. Java and generally implements more complex business logic.
If there are still some document-type models, this class will also implement the docaction Interface
This type can be directly applied to workflow to convert the document status.