LazyInitializationException when using join in CrudRepository

Question

getting org.hibernate.LazyInitializationException: could not initialize proxy - no Session when I call findByUserEmail(String email)

The service class (where I'm calling this function) is marked as @Transactional

Repository

@Repository
public interface UserImagesRepository extends CrudRepository<User_images, Integer> {
    List<User_images> findByUserEmail(String email);
}

User

@Entity
@Table(name = "users")
@NamedQuery(name = "User.findAll", query = "SELECT u FROM User u")
public class User implements Serializable {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private int id;

    private String email;

    @OneToMany(fetch = FetchType.LAZY, mappedBy = "user")
    private Set<User_images> images = new HashSet<User_images>(0);

    //getters and setters
}

User_images

@Entity
@Table(name = "user_images")
public class User_images implements Serializable {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private int id;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "userId")
    private User user;

    // getters and setters
}

___UPDATE___

The UserImageRepository has no implementation, queries are automatically generated from method name directly. docs

I don't want to use eager loading as its bad practice.

Can you share the implementation of findByUserEmail(String email) method? — Manish
– Manish, Commented May 25, 2015 at 12:47
FetchType.Lazy means that fetch when needed , so when you call findByUserEmail(String email),if in this fuction you are fetching some thing which is associated with another table after the service method call it will give the LazyInitailzation exception as session is closed.try replacing with fetch=FetchType.Eager all places , it should work. 1.javarevisited.blogspot.in/2014/04/… 2.uaihebert.com/four-solutions-to-the-lazyinitializationexception — Amar Agrawal
– Amar Agrawal, Commented May 25, 2015 at 13:01
Is the exception occurring inside the findByUserEmail method? Perhaps your stacktrace would help us, or even the actual code in this method. — DuncanKinnear
– DuncanKinnear, Commented May 26, 2015 at 1:08

Adrian Shum · Accepted Answer · 2015-05-26 01:57:07Z

Whenever you see something like org.hibernate.LazyInitializationException: could not initialize proxy - no Session, it is because of you are trying access a lazy-loading property outside transaction boundary.

In some case it is because you haven't setup transaction manager etc correctly, therefore once you get the entities from the repository, there is already no active Session.

In most case, you are trying to access lazy-loading property outside where you declared transactional. For example, there may be one Controller calling your Service (Your Service is where the transaction boundary is declared), and in the controller you are doing something like user.getImages(). You should make sure you have already fetched the images before you return from Service. (There are some other ways like "Open Session In View" but that's never my preferred solution).

Such kind of lazy property access may not be explicit, for example, it may be triggered by you are calling toString() of User because of logging, or you are using a debugger to inspect the content of User.

Off topic advise: Make sure you complies to Java's convention in naming. It should be UserImage instead of User_images

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