How to handle a PSQLException in java?

Question

I have a unique constraint on one of my entities and whenever I get a PSQLException which occurs whenever that constraint is violated, I want to respond with a bad request.

Answer 1

Key problem is that PSQLException is wrapped into some Spring exception (which I assume from your code); you have to unwrap it (for example using guava's Throwables):

public DepartmentForHoliday setDepartment(DepartmentForHoliday department) {
    if (department.getDepartmentId() == null) {
        Department savedDepartment = new Department();
        savedDepartment.setName(department.getName());
        try {
            departmentRepository.save(savedDepartment);
        } catch (RuntimeException e) {
            Throwable rootCause = com.google.common.base.Throwables.getRootCause(e);
            if (rootCause instanceof SQLException) {
                if ("23505".equals(((SQLException) rootCause).getSQLState())) {
                    // do smth interesting :)
                }
            }
        }
    }
}

Once you do that you can throw your custom exception and handle it in DatabaseExceptionHandler