Pre-Exit, Post-Exit, Overwrite Exit methods in webdynpro abap

Generally these methods are used in case of webdynpro abap enhancement scenario. You can easily enhance an existing application to modify some functions. E.g. you want to remove a button from a standard webdynpro screen. In such a scenario, you can enhance the standard webdynpro application and then remove the button. Now in this scenario when you go to that view controller methods tab, you can see 3 methods : Pre-Exit, Post-Exit, Overwrite Exit. These methods will provide you the flexibility to modify the standard screen logic.

Pre-Exit:              This method will call before WDDOINIT method of that view.  
Post-Exit:            This method will call after WDDOINIT method of that view.  
Overwrite Exit: This method will simply overwrite standard code and only follow the code written inside it.

So be careful while writing any logic in those methods.