Call method in JPA

Question

I'm using ObjectDB with JPA. I would like to call myMethod(). For example:

entityManager.createQuery("SELECT ... FROM ... WHERE MyClass.myMethod() = 100")

Is it possible? Maybe any annotation is required before method in the class?

@Entity
public class MyClass implements Serializable {

    @Basic 
    private int x;

    @Basic
    private int y;

    public int myMethod() {
        return x*1000+y;
    }
}

Answer 1

JPQL is not exactly an object-based query language. You can't define your own methods, and JPQL provides a very limited set of functions. So if you want to keep within the JPA spec then the answer is no; would have to be JPA-implementation specific - DataNucleus JPA certainly allows you to have your own methods in the query language (as a vendor extension), no idea about your quoted JPA provider - that said though, it would only execute such a query in the datastore if you put the code for that method in a query method implementation (as opposed to in the class)

Answer 2

Yes, you can! And no additional annotations are required.

ObjectDB is an implementation of an object-oriented database system (OODBS) and as a result allows you to interact with database items as objects, that includes calling methods, using inheritance and polymorphism, etc.

This is a simple working example I have. With a class like this:

@Entity
public class Person {
    private static final long serialVersionUID = 1L;

    @Id @GeneratedValue
    private long id;

    private String firstName;
    private String lastName;

    Person(String firstName, String lastName) {
        this.firstName = firstName;
        this.lastName = lastName;
    }

    public String getFullName() {
        return firstName + " " + lastName;
    }
}

This query returns correct results:

entityManager.createQuery(
    "SELECT p FROM Person p WHERE p.getFullName()='John Johnson'", Person.class).getResultList();