Question

I have two entities which are Student and Class entities.
Student and Class are many to one relationship. So student contains class attribute.

Now i want to save or create a student associate with existing class(means i know primary key ID already).

Solution 1:

Student student = new Student();
Class class = session.load(classId);  
student.setClass(class);
session.save(student);

Solution 2:

Student student = new Student();
Class class = new Class();
class.setClassId(classId);
student.setClass(class);
session.save(student);

My question here is in solution 1 it will issue two SQL, one is to get Class another is to insert student. But in solution 2 only need to have one SQL. If I have more class attribute,
i will load and issue more select sql before insert. It seems not that efficient. Is there any side-effect in solution 2?

which way to do save/insert is better? By the way, i do not set up cascade.

Thank you
Yee Chen

Answer 1

Solution 1 won’t issue an SQL query to load Class. Unlike get(), load() returns a proxy object with the specified identifier and doesn’t perform a database query immediately. Thus, load() method is a natural choice for this scenario (when you actually need to load an object, use get()).

Possible side effect of solution 2 depends on cascading configuration of relationship and so on. Even if it works fine in your current case, it makes your code more fragile, since seemingly unrelated changes in the code may break it.

So, I recommend you to use Solution 1 and don’t worry about performance.