Grails Don't Know How To Get Exception

Question

I try to save a duplicate book to my Book domain class for testing. I have a try-catch(Exception ex) to get the error.

BookService bookService

try {
   def book = new Book()
   book.id = 'Lord of the Flies'
   bookSerivce.save(book)
   def anotherBook = new Book()
   anotherBook.id = 'Lord of the Flies'
   bookService.save(anotherBook)
} catch (Exception ex) {
   System.out.println(ex.getMessage())
}

I use ex.getMessage(). I am getting this error message. This one is pretty much useless.

could not execute statement; SQL [n/a]; constraint [PRIMARY]; nested exception is org.hibernate.exception.ConstraintViolationException: could not execute statement

On the other hand, I am getting this error message from the command prompt console. This one I can use. It clearly says that I already have a book called 'Lord of the Flies' in the database.

2020-11-02 14:46:39.790 ERROR --- [eduler_Worker-1] o.h.engine.jdbc.spi.SqlExceptionHelper : (conn=665) Duplicate entry 'Lord of the Flies' for key 'PRIMARY'

I understand I should not use the catch-all Exception. I will need to use a more specific Exception class. I already tried catch (SQLException ex) but it did not catch the error. I also tried some others Exception classes but they didn't catch the error either.

It also looks like book.save() and bookSerive.save(book) throw a different Exception.

Would you show me which Exception class I can use in the catch() function to capture the correct error please?

Thanks!

Answer 1

The question and the comments below it aren't especially clear to me but something to investigate is the root cause of the exception:

BookService bookService

try {
   def book = new Book()
   book.id = 'Lord of the Flies'
   bookSerivce.save(book)
   def anotherBook = new Book()
   anotherBook.id = 'Lord of the Flies'
   bookService.save(anotherBook)
} catch (Exception ex) {
   System.out.println(ex.getMessage())
   Throwable t = ex.getCause()
   if(t) {
        // interrogate t as the root cause
   }
}