How this is happening in Hibernate?

[Kishor Joshi]

Hi there

I am using Hibernate to develop web application.I have a point that after saving values from my web application to database in localhost.When I undeploy application from my localhost.All values in saved database are also being deleted.However table structure is there but values are empty?

Why this is happening?

Thanks

[Roel De Nijs]

And are you sure the data is actually in the database (table) after saving the values (and before undeploying the application)?

And what kind of database are you using? MySQL? Oracle? Or an in-memory database perhaps?

[Kishor Joshi]

Ok this post might be lengthy

This is my model class

package collegemgtsystem.model;

import java.util.HashSet;
import java.util.Set;

import javax.persistence.Column;
import javax.persistence.ElementCollection;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Lob;
import javax.persistence.Table;

@Entity
@Table(name="Student_Info")
public class Student {
	
	@Id
	private String userId;
	
	private String userFirstName;
	
	private String userMiddleName;
	
	private String userLastName;
	
	private String userFatherName;
	
	private String userFatherEmp;
	
	private String userCourse;
	
	private String userBranch;
	
	private String courseFrom;
	
	private String courseTo;
	
	private String userDob;
	
	private String userEmail;
	
	private String userMobile;
	
    private String user10marksheet;
	
    private String user12Certificate;
    
    private String userGradCertificate;
    
    @ElementCollection
    @Column(name="Student_HighSchoolData")
    private Set<HighSchool> highSchoolData=new HashSet<HighSchool>();
    
    @ElementCollection
    @Column(name="Student_InterSchoolData")
    private Set<InterSchool> interSchoolData=new HashSet<InterSchool>();
    
    @ElementCollection
    @Column(name="Student_GradData")
    private Set<GradSchool>  graduationData=new HashSet<GradSchool>();
    
    @ElementCollection
    @Column(name="Student_ListOfAddress")
    private Set<Address> addressList=new HashSet<Address>();
    
    @Lob
    @Column(length=10000000)
    private byte[] userImage;

	public String getUserId() {
		return userId;
	}

	public void setUserId(String userId) {
		this.userId = userId;
	}

	public String getUserFirstName() {
		return userFirstName;
	}

	public void setUserFirstName(String userFirstName) {
		this.userFirstName = userFirstName;
	}

	public String getUserMiddleName() {
		return userMiddleName;
	}

	public void setUserMiddleName(String userMiddleName) {
		this.userMiddleName = userMiddleName;
	}

	public String getUserLastName() {
		return userLastName;
	}

	public void setUserLastName(String userLastName) {
		this.userLastName = userLastName;
	}

	public String getUserFatherName() {
		return userFatherName;
	}

	public void setUserFatherName(String userFatherName) {
		this.userFatherName = userFatherName;
	}

	public String getUserFatherEmp() {
		return userFatherEmp;
	}

	public void setUserFatherEmp(String userFatherEmp) {
		this.userFatherEmp = userFatherEmp;
	}

	public String getUserCourse() {
		return userCourse;
	}

	public void setUserCourse(String userCourse) {
		this.userCourse = userCourse;
	}

	public String getUserBranch() {
		return userBranch;
	}

	public void setUserBranch(String userBranch) {
		this.userBranch = userBranch;
	}

	public String getCourseFrom() {
		return courseFrom;
	}

	public void setCourseFrom(String courseFrom) {
		this.courseFrom = courseFrom;
	}

	public String getCourseTo() {
		return courseTo;
	}

	public void setCourseTo(String courseTo) {
		this.courseTo = courseTo;
	}

	public String getUserDob() {
		return userDob;
	}

	public void setUserDob(String userDob) {
		this.userDob = userDob;
	}

	public String getUserEmail() {
		return userEmail;
	}

	public void setUserEmail(String userEmail) {
		this.userEmail = userEmail;
	}

	public String getUserMobile() {
		return userMobile;
	}

	public void setUserMobile(String userMobile) {
		this.userMobile = userMobile;
	}

	public String getUser10marksheet() {
		return user10marksheet;
	}

	public void setUser10marksheet(String user10marksheet) {
		this.user10marksheet = user10marksheet;
	}

	public String getUser12Certificate() {
		return user12Certificate;
	}

	public void setUser12Certificate(String user12Certificate) {
		this.user12Certificate = user12Certificate;
	}

	public String getUserGradCertificate() {
		return userGradCertificate;
	}

	public void setUserGradCertificate(String userGradCertificate) {
		this.userGradCertificate = userGradCertificate;
	}

	public byte[] getUserImage() {
		return userImage;
	}

	public void setUserImage(byte[] userImage) {
		this.userImage = userImage;
	}

	public Set<HighSchool> getHighSchoolData() {
		return highSchoolData;
	}

	public void setHighSchoolData(Set<HighSchool> highSchoolData) {
		this.highSchoolData = highSchoolData;
	}

	public Set<InterSchool> getInterSchoolData() {
		return interSchoolData;
	}

	public void setInterSchoolData(Set<InterSchool> interSchoolData) {
		this.interSchoolData = interSchoolData;
	}

	public Set<GradSchool> getGraduationData() {
		return graduationData;
	}

	public void setGraduationData(Set<GradSchool> graduationData) {
		this.graduationData = graduationData;
	}

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

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

This is my bean.xml file

<bean id="registerStudentBeanCreate"  class="org.springframework.orm.hibernate4.LocalSessionFactoryBean">
   <property name="dataSource" ref="dataSource"></property>
    <property name="annotatedClasses">
    <list>
        <value>collegemgtsystem.model.Student</value>
    </list>
    </property>
    <property name="hibernateProperties">
                <props>
                  <prop key="hibernate.dialect">org.hibernate.dialect.MySQLDialect</prop>
                  <prop key="hibernate.show_sql">false</prop>
                  <prop key="hibernate.current_session_context_class">thread</prop>
                  <prop key="hibernate.hbm2ddl.auto">create</prop>
                </props>
    </property>
</bean>

<bean id="registerStudentBeanUpdate"  class="org.springframework.orm.hibernate4.LocalSessionFactoryBean">
   <property name="dataSource" ref="dataSource"></property>
    <property name="annotatedClasses">
    <list>
        <value>collegemgtsystem.model.Student</value>
    </list>
    </property>
    <property name="hibernateProperties">
                <props>
                  <prop key="hibernate.dialect">org.hibernate.dialect.MySQLDialect</prop>
                  <prop key="hibernate.show_sql">false</prop>
                  <prop key="hibernate.current_session_context_class">thread</prop>
                  <prop key="hibernate.hbm2ddl.auto">update</prop>
                </props>
    </property>
</bean>

<bean id="registerationDaoCreate" class="collegemgtsystem.dao.RegistrationDaoImpl">
   <property name="factory" ref="registerStudentBeanCreate"></property>
</bean>

<bean id="registerationDaoUpdate" class="collegemgtsystem.dao.RegistrationDaoImpl">
   <property name="factory" ref="registerStudentBeanUpdate"></property>
</bean>

This is my dao Impl class

public class RegistrationDaoImpl implements RegistrationDao {
	
	private SessionFactory factory;
	
	public SessionFactory getFactory() {
		return factory;
	}

    public void setFactory(SessionFactory factory) {
		this.factory = factory;
	}

    @Override
	public void saveStudent(Student s) {
		System.out.println("Inside registerStudent");
		Session session=this.getFactory().openSession();
		Transaction tx=session.beginTransaction();
		session.persist(s);
		tx.commit();
		session.close();
	    System.out.println("Exiting registerStudent");
    }

}

and this is MyServlet code from where I am calling this Dao method

public void registerUser(){
		System.out.println("Inside RegisterUser()");
		if(regFlag==0){
		ApplicationContext context=WebApplicationContextUtils.getRequiredWebApplicationContext(getServletContext());
		
		RegistrationDao registrationDao=(RegistrationDao) context.getBean("registerationDaoCreate");
		
		registrationDao.saveStudent(rs);
		}
		
		else{
			ApplicationContext context=WebApplicationContextUtils.getRequiredWebApplicationContext(getServletContext());
			
			RegistrationDao registrationDao=(RegistrationDao) context.getBean("registerationDaoUpdate");
			
			registrationDao.saveStudent(rs);
		}
		System.out.println("Exiting Registeruser()");
	}

I hope know its more clear

[Roel De Nijs]

Kishor Joshi wrote:I hope know its more clear

No, it's not! I asked 2 pretty straightforward questions. You replied with a very lengthy post but it doesn't answer either of my questions...

I also wonder why you have a Dao class for updating and another one for creating. I have never seen this approach. You have a Dao interface (and implementing class) with CRUD methods.

[Kishor Joshi]

I also wonder why you have a Dao class for updating and another one for creating. I have never seen this approach. You have a Dao interface (and implementing class) with CRUD methods.

because if i will use only create command then it will always create a new table previous record will be delete.
If I use only update when first time I run I will get exception that table not exists.

So I have made a custom logic if request is first time or already a table is created.

[Roel De Nijs]

I would never rely on hbm2ddl in a production environment. It's ok for development purposes, but a risk for a production envorinment. I always create my database scripts manually and execute them manually.

And it seems it's not only me who doesn't want to rely on hbm2ddl in a production environment. Here and here you'll find more user experiences.

Hope it helps!
Kind regards,
Roel

[Kishor Joshi]

So what you suggest in my case to change this ?

[Roel De Nijs]

write the ddl statements (to create/alter tables and other database objects) yourself and execute them manually
don't use hbm2ddl in your application
write 1 Dao for each entity with create, read, update, delete, find and other required methods

consider Spring to handle transaction management using annotation instead of creating transactions in the code yourself. And if you do, consider Spring Data JPA as well.

[Paul Clapham]

As for why Hibernate recreates empty database tables before each run (if that's what's actually happening): there's a configuration property which tells Hibernate to do that (or not). It's this one, if I'm not mistaken:

<prop key="hibernate.hbm2ddl.auto">create</prop>

[Kishor Joshi]

I will update my post soon on this topic