what is trigger event for put request method. for example for get after_retrieve, for post after_save and for delete after_delete is there.
PUT will execute the before_save and after_save the same way as the POST, in the before_save you can check to see if the bean ID is set, if it is, then you are updating an existing record, if you are entering a new bean the ID will not be set since it is created when the record is saved.
Also, in the before_save, if you are updating a record you will have values in the bean's fetched_row
which contains the bean before the edit so you can compare the old values to the new in your logic.
If you are entering a new bean then there will be no fetched_row, so that's another way to check if you are creating a new record or modifying one.