Hibernate lazy fetch unable to load child objects

Question

I have parent object with lots of child objects so cant use EAGER. I've tried multiple styles to get all the child objects of parent, but the below size code, and everything else i've tried throws

failed to lazily initialize a collection of role xxxx, could not initialize proxy - no Session

How do i initialize all the child objects ? do i really need to make another query for all of them. Seems kinda stupid.

    @Transactional
    public List<XXX> findYYYinXXX(Long id) {
        List<XXX> list = xxxRepo.findYYY(id);
        for (XXX p : list){
            p.getChild().size();
        }
        return list;
    }

Hibernate.initialize(p.getChild); used inside for loop also throws the same error

you can use Hibernate.initialize in your DAO layer and not in your service, in order to have session still opened — Pierpaolo Di Dato
– Pierpaolo Di Dato, Commented Sep 3, 2018 at 12:28

Mathias G. · Accepted Answer · 2018-09-04 11:34:56Z

1

In your parent class use fetch type Eager.

1) use eager fetch type.

like @OneToMany(fetch = fetchType.Eager)

2) use join fetch query.

While creating query use fetch join.

eg. String hql = "select p from ParentClass p join fetch p.child_class_instance;

AS A SIDE MENTION: using @ElementCollections in this case at least requires using @CollectionTable(name="TABLENAME", schema = "SCHEMANAME")

edited Sep 4, 2018 at 11:34

Mathias G.

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answered Sep 3, 2018 at 11:28

Angad Bansode

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3 Comments

Clomez Over a year ago

I'll try the second but the question literally starts with "I have parent object with lots of child objects so cant use EAGER."

Angad Bansode Over a year ago

try the second one and apply where condition in hql if require to filter the output.

Clomez Over a year ago

Says it cant find table. Join seems to use camelcase table names tho. not sure why

gabrielgiussi · Accepted Answer · 2018-09-03 11:34:08Z

1

If you are using lazy=extra the proxy collection is not initialized when calling size or isEmpty See this answer. You could get the first child instead of calling size.

However your question doesn't make sense because you want EAGER fetching but you are trying to force child loading. I think that what you really want is to make the client of this findYYYinXXX be part of the transaction as well, so if it needs to load the childs it will not fail.

answered Sep 3, 2018 at 11:34

gabrielgiussi

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Comments

Shawn Alagheband · Accepted Answer · 2018-09-04 07:47:35Z

1

if you are using spring-boot you can set the following property in you application.properties file to keep lazy loading:

spring.jpa.properties.hibernate.enable_lazy_load_no_trans=true

edited Sep 4, 2018 at 7:47

answered Sep 3, 2018 at 11:44

Shawn Alagheband

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1 Comment

Clomez Over a year ago

Tried to put this in application.properties and into databaseConfig class, neither seem to have any impact. Still wont load child objects

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