# An efficient way to initialize a list of Hibernate proxies linked to different objects

**URL:** <https://discourse.hibernate.org/t/an-efficient-way-to-initialize-a-list-of-hibernate-proxies-linked-to-different-objects/893>\
**Category:** Hibernate ORM\
**Created:** [June 7, 2018, 12:45pm UTC](https://discourse.hibernate.org/t/an-efficient-way-to-initialize-a-list-of-hibernate-proxies-linked-to-different-objects/893 "2018-06-07T12:45:09Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![anonmoto](https://avatars.discourse-cdn.com/v4/letter/a/41988e/32.png) [@anonmoto](https://discourse.hibernate.org/u/anonmoto)\
**Post date:** [June 7, 2018, 12:45pm UTC](https://discourse.hibernate.org/t/an-efficient-way-to-initialize-a-list-of-hibernate-proxies-linked-to-different-objects/893/1 "2018-06-07T12:45:09Z")

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I have a number of JPA classes containing fields of a certain type in various combinations. This looks like this:

```auto
// entity to initialize
@Entity
class Type {
  ...

  @ManyToOne(fetch = LAZY)
  B b;
}

// containers

@Entity
class A {
  ...

  @ManyToOne(fetch = LAZY)
  Type type;
}

@Entity 
public class B {
  ...

  @ManyToOne
  C c;

  @OneToMany(fetch = LAZY)
  List<Type> possibleTypes;
}

@Entity
public class C {
  ...

  @OneToMany
  List<B> b;

  @OneToOne(fetch = LAZY)
  Type type;
}

```

Is there a way to initialize all `Type` proxies with one `SELECT` without building a manual request or initializing fields one by one with a number of `Hibernate.initialize()` calls? Something like

```auto
Set<Type> possibleProxies = new HashSet<>();
possibleProxies.add(a1.getType());
for (B b : c1.getB()) {
  possibleProxies.addAll(b.getPossibleTypes());
}
possibleProxies.add(c1.getType());
initializeAll(possibleProxies);

```

so that Hibernate or related library would check if some of the objects are already initialized and build a correct `SELECT` query according to JPA mapping.

---

<div class="post-metadata">

**Author:** ![vlad](https://yyz1.discourse-cdn.com/flex035/user_avatar/discourse.hibernate.org/vlad/32/658_2.png) [@vlad](https://discourse.hibernate.org/u/vlad)\
**Post date:** [June 7, 2018, 1:11pm UTC](https://discourse.hibernate.org/t/an-efficient-way-to-initialize-a-list-of-hibernate-proxies-linked-to-different-objects/893/2 "2018-06-07T13:11:47Z")

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There is no such feature. This is because you rarely want to traverse all associations and ending up fetching the entire database with a single method call.

You could JOIN FETCH the to-one associations and a to-many association as well. For the other associations, you could use a Reflection-based tool to trigger the initialization, although this might not be desirable.

If your goal is to transform the entities to DTOs, better fetch them as DTOs using a [ResultTransformer](https://vladmihalcea.com/why-you-should-use-the-hibernate-resulttransformer-to-customize-result-set-mappings/).

---

<div class="post-metadata">

**Author:** ![anonmoto](https://avatars.discourse-cdn.com/v4/letter/a/41988e/32.png) [@anonmoto](https://discourse.hibernate.org/u/anonmoto)\
**Post date:** [June 7, 2018, 1:18pm UTC](https://discourse.hibernate.org/t/an-efficient-way-to-initialize-a-list-of-hibernate-proxies-linked-to-different-objects/893/3 "2018-06-07T13:18:15Z")

</div>

Thanks for the answer!  
I suppose I’ll have to implement this feature manually.  
JOIN FETCH or ResultTransformer is not an option here because I have to perform the initial request to DB and proxy initialization (required for mapping to DTO) in 2 separate services divided by a massive business logic layer which may filter out 90% of the selected entities…