[FIXED] "could not initialize proxy - no Session" For Multiple ManyToMany relationships in the parent

Issue

I have a Parent User Class that has multiple ManyToMany Relationships.

@Table(name = "user")
public class User {
    ..
    @ManyToMany(fetch = FetchType.LAZY, cascade = {CascadeType.MERGE, CascadeType.DETACH})
    @JoinTable(
        name =  "user_address",
        joinColumns = { @JoinColumn(name = "user_id")},
        inverseJoinColumns = { @JoinColumn(name = "address_id")}
    )
    @JsonIgnore
    private final List<Address> addresses = new ArrayList<Address>();

    @ManyToMany(fetch = FetchType.LAZY, cascade = {CascadeType.MERGE, CascadeType.DETACH})
    @JoinTable(
        name =  "reports",
        joinColumns = { @JoinColumn(name = "user_id")},
        inverseJoinColumns = { @JoinColumn(name = "reports_id")}
    )

    @JsonIgnore
    private final List<Reports> reports = new ArrayList<Reports>();
}

When I access the FIRST ManyToMany property, everything works fine. However, immediately after accessing the first, when I try to access the SECOND ManyToMany Property I get the "could not initialize proxy - no Session" exception:

@Component
public class Combiner {
    public void combineData() {
        ...
        List<Address> addresses = user.getAddress(); // This works
        List<Reports> reports = user.getReports();   // Get the error here
        ..
    }
}

The Address and Reports classes have the inverse relationship as many ManyToMany back to the User Entity Above.

public class Address {
    @ManyToMany(mappedBy = "addresses", fetch = FetchType.LAZY)
    private final List<User> users = new ArrayList<User>();
}

public class Reports {
    @ManyToMany(mappedBy = "reports", fetch = FetchType.LAZY)
    private final List<User> users = new ArrayList<User>();
}

I tried searching SO for the same error where there are MULTIPLE relationships like mine and the first passes but second fails, but could'nt find a post (or google couldn't understand the search terms, if anyone knows a pre-existing one - please let me know). Could someone assess what else Im missing?

I've tried these so far to no avail:

• Added @Transactional to the parent Service class that calls Combiner above
• Made the second failing relationship EAGER. (as i understand it you cant make BOTH EAGER since i get a multiple bags error probably because of Cartesian join)

AM Using SpringBoot (2.2.4) with Hibernate Core {5.4.10.Final}

Solution

Approach one: Make @ManyToMany uni-directional. The exception clearly says it can not initialize the collection of role you have in User class.

As you asked in the comment section Why can't this use case be Bi Directional - You can make this bi-directional as well.
Approach two: make collection of role EAGER or use Hibernate.initialize() to initialize the collection.

Bonus: you can make both collection EAGER by using Set not List.

Answered By - Erfan Ahmed