我将如何使用jpa在jpa对象列表中查询参数

Question

I don't know exactly how to phrase this question unfortunately.

I have two tables that are only loosely related, PERSON and ASSIGNMENT.

public class Person {

    @EmbeddedId
    @Column
    PersonPK id;

    @Column
    String otherStuff;
}

public class PersonPK {

    @Column
    long personNumber;

    @Column
    Date hireDate;

    @Column
    Date terminationDate;
}

public class Assignment {
    @Id
    @Column
    long id;

    @Column
    long personId;

    @Column
    boolean active;

    @Column
    String otherStuff;
}

The PERSON one is easy to get with FROM Person p WHERE [current date in between hire and termination]

But i need to do a second query for assignments and I'd like to just pass the list of Persons back in instead of stripping out the id. So something like FROM Assignment a WHERE a.personId IN :persons.id.id AND a.active = true

Is this possible with a JPA query?

Answer 1

It seems a little curious to have an @EmbeddedId with date fields like that. To be honest I'd lose the PersonPK class and do something like this:

public class Person {
    @Id
    @Column
    long personNumber;

    @Column
    Date hireDate;

    @Column
    Date terminationDate;

    @Column
    String otherStuff;
}

public class Assignment {
    @Id
    @Column
    long id;

    @ManyToOne
    Person person;

    @Column
    boolean active;

    @Column
    String otherStuff;
}

Then you should be able to query by passing in the list of people:

List<Person> people = /* your list of people */
Query query = manager.createQuery("select a from Assignment a where a.person in :people");
query.setParameter("people", people);
List<Assigment> assignments = query.getResultList()

This works, because you are actually making a link between the Person and Assignment classes with the @ManyToOne annotation.

Edit: Seeing as you can't change the schema I'd just add a static helper to person to get the personNumbers for you:

public static List<Long> toPersonNumbers(List<Person> people) {
    List<Long> numbers = new ArrayList<Long>();
    for ( Person person: people ) {
        numbers.add(person.id.personNumber);
    }
    return numbers;
}

Then you can just call that when you need to set the params:

List<Person> people = /* your list of people */
Query query = manager.createQuery("select a from Assignment a where a.personId in :people");
query.setParameter("people", toPersonNumbers(people));
List<Assigment> assignments = query.getResultList()