当没有对象与键相关联时，应该抛出什么异常？

Question

I have an API where I am checking whether there are any existing objects available for a given key. If available, then update the existing object, otherwise create new object and save it.

If there is a case in which the key is available, but no object is linked to it, which exception should be thrown?

Answer 1

It really depends on how you want to build your API. I think hhe first thing you need to decide is: should this exception be caught by caller or not necessarily? In other words, is it a RuntimeException or not?

I guess that if you want to throw an exception, it's because your data model should not have empty / null objects for a given key. So, I would argue for an IllegalStateException or NoSuchElementException , which extends RuntimeException . It means that the caller is not forced to catch the exception.

If you want to force caller to catch the exception I would suggest you create your own exception that just extends Exception

---

EDIT:

For instance, a class named "MissingValueException" and defined as follow:

public class MissingValueException extends Exception {
    private static final long serialVersionUID = 1L;

    public MissingValueException(final String message) {
        super(message);
    }

    public MissingValueException(final String message, final Exception root) {
        super(message, root);
    }
}