无法使用休眠从映射表获取数据

Question

Hi i am new to hibernate.

I have a java web project and i am using spring mvc with hibernate in this project and for database i am using my sql.

The issue i am facing is that : i have a table in db as user and in java project as user.java and i have another table references and in java project i have referances.java and i have created a mapping table as user_referances_mapping(user_id, referance_id).

and i have one to many relationship between user and referances table.

Now when i try to get the user data it gives me user table coloumns data but not the referances data and returns only null list for referances table.

On the other hand i also have similar mapping tables with user table like role, address with one to many mapping only and data is getting retrieved from those tables.

So can anyone help me getting the solution, that why i am not getting the data of the referances table using the one to many relationship and what should be the solution to it.

mapping of referances table in user table:

@OneToMany
@Basic(optional = true)
@BatchSize(size = 5)
@Cascade(CascadeType.ALL)
@Cache(region = IAppConstants.CACHE_REFERANCES, usage = CacheConcurrencyStrategy.READ_WRITE)
@JoinTable(name = "user_referances_mapping", joinColumns = { @JoinColumn(name = "user_id") }, inverseJoinColumns = { @JoinColumn(name = "referance_id") })
private List<Referances> referances = new ArrayList<Referances>();

public List<Referances> getReferances() {
    return referances;
}

public void setReferances(List<Referances> referances) {
    this.referances = referances;
}

UserDao class function :

public User getC2SUserByContactNoOrEmail(final String value) throws ApplicationException {
    try{
    @SuppressWarnings("unchecked")
    Query query = currentSession().createQuery(
            IQueryConstants.FETCH_USER_BY_CONTACTNO_OR_EMAIL);
    query.setParameter("contactNo", value);
    query.setParameter("email", value);
    return (User) query.uniqueResult();
    }catch(Exception e){
        throw new ApplicationException(
                "Issue occurred while fetching user by: " + value, e);
    }
    //return null;
}

FETCH_USER_BY_CONTACTNO_OR_EMAIL = "FROM User WHERE contactNo=:contactNo or email=:email";

Answer 1

If I'm right, the OneToMany relations are defined as "lazy" by default, which means you need to explicitly state that you want to fetch the related records.

Try modifying the query like this:

FETCH_USER_BY_CONTACTNO_OR_EMAIL = "FROM User u LEFT JOIN FETCH u.referances WHERE u.contactNo=:contactNo or u.email=:email";