org.hibernate.LazyInitializationException

Question

Student.java

package Model;


import java.util.Set;

public class Student {
private int studentID;
private  String name;
private String city;
private Set<Address> AddressList;
private Set<Contact> ContactList;

public Set<Contact> getContactList() {
    return ContactList;
}

public void setContactList(Set<Contact> contactList) {
    ContactList = contactList;
}

public Set<Address> getAddressList() {
    return AddressList;
}

public void setAddressList(Set<Address> addressList) {
    AddressList = addressList;
}

public int getStudentID() {
    return studentID;
}

public void setStudentID(int studentID) {
    this.studentID = studentID;
}

public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}

public String getCity() {
    return city;
}

public void setCity(String city) {
    this.city = city;
}

}

Address.java

package Model;

public class Address {

private int Aid;
private String fullAddress;
//private Student student;
/*public Student getStudent() {
    return student;
}
public void setStudent(Student student) {
    this.student = student;
}*/
public int getAid() {
    return Aid;
}
public void setAid(int aid) {
    Aid = aid;
}
public String getFullAddress() {
    return fullAddress;
}
public void setFullAddress(String fullAddress) {
    this.fullAddress = fullAddress;
}
}

Contact.java

package Model;

public class Contact {
private int contactId;
private String mobileNo;

public int getContactId() {
    return contactId;
}
public void setContactId(int contactId) {
    this.contactId = contactId;
}
public String getMobileNo() {
    return mobileNo;
}
public void setMobileNo(String mobileNo) {
    this.mobileNo = mobileNo;
}



 }

Student.hbm.xml

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="Model.Student" table="Student">
    <id name="studentID" type="int">
        <column name="StudentID" />
        <generator class="identity" />
    </id>
    <property name="name" type="java.lang.String"/>
    <property name="city" type="java.lang.String"/>
    <set name="AddressList">
        <key column="studentID"/>
        <one-to-many class="Model.Address"/>        
    </set>
    <set name="ContactList">
        <key column="studentID"/>
        <one-to-many class="Model.Contact"/>        
    </set>
</class>

Address.hbm.xml

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="Model.Address" table="Address">
    <id name="Aid" type="int">
        <column name="Aid" />
        <generator class="identity" />
    </id>
    <property name="fullAddress" type="java.lang.String"/>
</class>

Contact.hbm.xml

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="Model.Contact" table="Contact">
    <id name="contactId" type="int">
        <column name="contactId" />
        <generator class="identity" />
    </id>
    <property name="mobileNo" type="java.lang.String"/>
</class>

Main method.

public static void main(String[] args)
{
    Configuration cfg=new Configuration();
    cfg.configure("hibernate.cfg.xml");
    SchemaExport se=new SchemaExport(cfg);
    se.setOutputFile("D:\\abc.sql");
    se.create(true,true);//create(boolean script, boolean export) 

    System.out.println("------------------Saving of Student--------------------");
    Student student =new Student();
    student.setName("Yograj");
    student.setCity("Nanded");
    Set<Address> addressList=new HashSet<Address>();
    Address address=new Address();
    address.setFullAddress("Chikhali Nanded");
    addressList.add(address);
    address=null;
    address=new Address();
    address.setFullAddress("karvenagar Pune");
    addressList.add(address);
    student.setAddressList(addressList);

    Set<Contact> contactList=new HashSet<Contact>();
    Contact contact=new Contact();
    contact.setMobileNo("9403330577");
    contactList.add(contact);
    contact=null;
    contact=new Contact();
    contact.setMobileNo("9890864805");
    contactList.add(contact);
    student.setContactList(contactList);

    boolean result=new StudentServices().SaveStudent(student);

    if(result)
    {
        System.out.println("------------------Save Student succ..--------------------");
    }
    else
    {
        System.out.println("------------------Saving failed--------------------");
    }

    System.out.println("------------------Student Details--------------------");
    List<Student> studentList=new StudentServices().GetStudentlist();
    for (Student stud : studentList) {
        System.out.println("Name:"+stud.getName());
        System.out.println("City:"+stud.getCity());
        for (Address add : stud.getAddressList()) {
            System.out.println("Full Address:"+add.getFullAddress());
        }
        for (Contact cont : stud.getContactList()) {
            System.out.println("Full Address:"+cont.getMobileNo());
        }
    }
    System.out.println("Execution over.");


}

StudentService.Java

package Service;

import java.util.List;

import javassist.runtime.Inner;

import org.hibernate.Criteria;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
import org.hibernate.criterion.Restrictions;
import org.hibernate.sql.JoinType;

import Model.Address;
import Model.Contact;
import Model.Student;

public class StudentServices {
public boolean SaveStudent(Student student) {
    try {
        Configuration cfg = new Configuration().configure();
        SessionFactory sf = cfg.buildSessionFactory();
        Session session = sf.openSession();
        Transaction transaction = session.beginTransaction();

        session.save(student);
        for (Address add : student.getAddressList()) {
            session.save(add);

        }
        for (Contact cont : student.getContactList()) {
            session.save(cont);

        }
        transaction.commit();
        session.close();
        return true;
    } catch (HibernateException e) {
        return false;
    }
}

public List<Student> GetStudentlist() {
    try {
        Configuration cfg = new Configuration().configure();
        SessionFactory sf = cfg.buildSessionFactory();
        Session session = sf.openSession();
        Transaction transaction = session.beginTransaction();
        Criteria criteria = session.createCriteria(Student.class, "Student")
                .createAlias("Student.AddressList", "Address",JoinType.INNER_JOIN)
                .createAlias("Student.ContactList", "Contact",JoinType.INNER_JOIN);
        List<Student> studentList = criteria.list();

        transaction.commit();
        session.close();
        return studentList;
    } catch (HibernateException e) {
        return null;
    }
}
}

When i execute main method hibernate will create database and table.in all table it will store records but when i fetch records using criteria API it gives me error "org.hibernate.LazyInitializationException."

score 1 · Accepted Answer · answered Jan 23 '13 at 13:54

In your case student.addressList and student.contactList use lazy loading. Lazy loading means, the values are not loaded together with the studentList, but only then when you access them with getAddressList()and getContactList.

Lazy loading only works as long as the session is still open. If not yet loaded components are accessed after closing the session a LazyInitializationException is thrown, as in your example.

What you are doing is:

in GetStudentlist: open the session
in GetStudentlist: load all students
in GetStudentlist: close the session
in main: for each student
in main: access the address list via student.getAddressList()

This throws in exception in step 5, because you access the address list, which applies to lazy loading, and the data can't be loaded any more, because the session already was closed in step 3.

You must close the session after calling getAddressList() and getContactList(), then it works.

By the way, when you only read data as in GetStudentlist, then you do not need to begin a transaction, and you do not need to commit anything.

But i worked in nhibernte for one year the same code works fine in ASP.NET MVC 3 so can we say its the difference between Nhibernate and Hibernate. — Amogh, Jan 23 '13 at 14:04
in Nhibernate if put lazy=true in mapping and if we use criteria API for innerJoin and return student list then Addresslist is accessible after closing od session also... — Amogh, Jan 23 '13 at 14:21
In Hibernate (without 'N') this is not the case. You only can access lazy loaded members after the session close if you've already accessed them at least once before closing the session. By the way, lazy loading is used by default. — Johanna, Jan 23 '13 at 16:13

score 0 · Answer 2 · answered Jan 23 '13 at 12:28

0

Try to access a method in student to initialize the proxy.

Try calling student.getAddress().getFullAddress() in your service method in order to initialize the proxy.

In this way, you will avoid the lazy initialization exception.

The other way is to set eager fetching to true, but i'd rather go with the first method first.

answered Jan 23 '13 at 12:28

grassbl8d

1,989
4
22
30

but when i try to implement same exeample in ASP.MVC with nhibernate its works not need to call student.getAddress().getFullAddress() in your service method then what makes spring MVC different. – Amogh Jan 23 '13 at 12:40

score 0 · Answer 3 · edited May 23 '17 at 12:23

For Junit testcases you need to bind an opened Session to the current Thread.

//the following is necessary for lazy loading
SessionFactory sf = null;

// open and bind the session for this test thread.
Session s = null;

// Session holder
SessionHolder holder = null;

BeanFactory beanFactory = null;

protected void onSetUp() throws Exception {
    System.out.println("On SetUP----");
    sf = (SessionFactory) beanFactory.getBean("sessionFactory");
    s = sf.openSession();
    TransactionSynchronizationManager.bindResource(sf, new SessionHolder(s));
}


protected void onTearDown() throws Exception {
    System.out.println("On onTearDown----");
    // unbind and close the session.
    holder = (SessionHolder) TransactionSynchronizationManager.getResource(sf);
    s = holder.getSession();
    s.flush();
    TransactionSynchronizationManager.unbindResource(sf);
    SessionFactoryUtils.closeSession(s);
    // SessionFactoryUtils.releaseSession(s, sf);
    // teardown code here
}

If you want to no more care about LazyInitialisationException read this, its well explain what happens, and how to resolve the problem definitely

org.hibernate.LazyInitializationException

3 Answers3