When I entered the Register interface, I entered a mailbox that did not comply with the rules of mailbox setting, but the system did not correctly prompt that the entered mailbox was incorrect. The process of reproducing: 1. Find the location where we need to modify the exception handling. 2. Add a piece of regular matching code to the register() method in the Register class. 3. Do a unit test to check if the new code is working well. 4. Pass testing, the bug fixed.