CODEWITHSUNDEEP
javahibernatelazy-loadingfetch
Jar
Jar

Reputation: 61

Hibernate LAZY fetch not initializing an instance

I encountered a problem with lazy association two days ago and still haven't found an explanation of such a behavior. Here is my simplified class hierarchy:

@Entity
@Table(name="A")
public class A
{
    @Id
    @GeneratedValue
    @Column(name="ID")
    private int id;
    @OneToMany(mappedBy="a", fetch=FetchType.LAZY, cascade=CascadeType.ALL) 
    private Set<B> listB = new HashSet<B>();
}

@Entity
@Table(name="B")
public class B
{
    @Id
    @GeneratedValue
    @Column(name="ID")
    private int id;
    @ManyToOne(fetch=FetchType.LAZY)
    @JoinColumn(name="A_ID")
    private A a;
    @ManyToOne(fetch=FetchType.LAZY)      // ERROR!
    // @ManyToOne(fetch=FetchType.EAGER)  // OK
    @JoinColumn(name="C_ID")
    private C c;
}

@Entity
@Table(name="C")
public class C {
    @Id
    @GeneratedValue
    @Column(name="ID")
    private int id; 
}

When I try to read simple structure from db: A->B->C i get the following results:

System.out.println(a.getId());                  // 1
for (B b : a.getListB()) {                      
    System.out.println(b.getId());              // 1
    C c = b.getC();
    System.out.println(c.getId());              // 0 !!!
}

As you can see instance of C is not properly initialized. After changing fetch type from LAZY to EAGER for field c in class B everything works!

I suspect there is is some CGLIB magic, but can't find a clue nether in the specification nor in Google. Could someone explain this?

Thanks for any help!!!

Upvotes: 4

Views: 1339

Answers (2)

Jar
Jar

Reputation: 61

Fixed. My question was not correct. Sorry. There was final modifier for getters and setters of my entitiy classes. It breaks single value associations like many-to-one. Suppose I've missed some warnings in hibernate logs... I think it would be better to throw an exception by hibernate for this case.

Upvotes: 0

Bharat Sinha
Bharat Sinha

Reputation: 14373

In case you would like to understand lazy loading see this answer; it defines it pretty well.

Upvotes: 1

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