More complex custom validations can be implemented using the @AssertTrue annotation. The following list an example method added to the User class:

    @AssertTrue(message = "Password fields don't match") 
    private boolean isValid() { 
      return this.password.equals(this.password2); 
    }

@AssertTrue(message = "Password fields don't match") is the message to be shown if the validation fails.

Any complex validation logic with multiple fields can be implemented in these methods.