What Is business logic

Business logic is the logic that processes data. The general background code is also divided into three layer Action (Controller) service DAO (here The three layer is not MVC)

For example, I get the username, but when I save the database, the user name field should be the foreground user name plus the current date to spell the string

Action or controller layer is the first layer is generally used to accept data and do not empty AH format is the correct authentication
  If the user name is empty is not a secure string, such as

The service layer is typically used to make a business logic implementation
  At this time UserName = UserName + new Date ();

The DAO layer is the interaction layer with the database
  That is, the read-write database inserts the new username from the logical layer into the database

What Is business logic