Difference between lazy loading and eager loading in JPA?

Question

public class University {
    private String id;
    private String name;
    private String address;
    private List<Student> students;

    // setters and getters
}

In lazily loading when I load a University from the database, JPA loads its id, name, and address fields for me. Students will not load. When I call getStudents() method, JPA will then execute the query

select * from students where universitycode=id

Is my understanding of lazy loading correct?

Tomasz Nurkiewicz · Accepted Answer · 2012-10-03 12:44:31Z

3

Correct. If you use eager loading on the other hand, JPA will proactively load students for you and return fully-populated University object.

Whether single JOIN query will be used or two separate queries is up to the JPA provider (EclipseLink, Hibernate...)

answered Oct 3, 2012 at 12:44

Tomasz Nurkiewicz

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