I did this simple Spring Security tutorial. https://www.boraji.com/spring-mvc-5-spring-security-5-hibernate-5-example
Now I want to create a user in my database.
The problem is that I need to create 2 objects dependent on each other and I get
org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance beforeQuery flushing:
So What's the solution for this??
public static boolean createUser(byte[] image, String name, String username, String password, String permissions) {
String hashedPassword = new BCryptPasswordEncoder().encode(password);
//check if user already exists
boolean exists = User.checkIfUserExists(username);
//if it doesn't add to database
if(!exists) {
UserRole userRole = new UserRole();
User user = new User();
userRole.setRole(permissions);
userRole.setUser(user);
Database.addToDatabase(userRole);
//user table
user = new User(image, name, username, true, hashedPassword, userRole);
Database.addToDatabase(user);
//user role table
userRole.setUser(user);
Database.updateObject(userRole);
return true;
}
else
return false;
}
//Save the object to the database
public static void addToDatabase(Object object) {
SessionFactory factory = HibernateUtil.GetSessionFactory();
Session session = factory.openSession();
Transaction tx = null;
try{
tx = session.beginTransaction();
session.save(object);
tx.commit();
}catch (HibernateException e) {
if (tx!=null) tx.rollback();
e.printStackTrace();
}finally {
session.close();
}
}
Basically UserRole already needs to be in db to save User and User needs to be in db to save UserRole.
That exception means exactly what is written. You have a relationship between two objects. For example UserRole has a linked User. But when you are trying to save the UserRole into the database the User object you have attached to it is not yet saved (it is in transient state) so Hibernate's problem is how to save that user role in the database when the user might not exist (it still doesn't have valid ID in the database ).
There are different ways you can deal with that. One of them is to mark the list as Cascade=ALL (or Cascade=SAVE_UPDATE). This way you will bind these two objects and when you save the user it will automatically save the user role. There are pros and cons with that. The "+" is that it is easier and you will have just one save. The "-" is that you have these objects connected and you might save/update an object by mistake if you are not careful.
Another solution would be to first save the User (without the roles). Then save the roles with the user set to the newly saved user (it should have a real ID in the database). Then add the roles to the user and update it. This way you will not save anything with transient values and you will go around that problem. Also do it in a transaction so you don't have bad data if something breaks.
I'm new to hibernate and as I researched, I have found out that the HQL insert query gets data from other tables. According to what I've read, I can make use of session.save for the insert functionality.
In my DAO I have this addToCart() method
#Override
public void addToCart(ShoppingCart cart) {
Session session = HibernateUtil.getSessionFactory().openSession();
Transaction transaction = session.beginTransaction();
session.save(cart);
transaction.commit();
session.close();
}
The code above doesn't work. Maybe I am missing something because I'm still new to hibernate.
im having javax.jdo.JDODetachedFieldAccessException when i want to, after retrieve all of my Entites as a List in my DAO implementation, ask for one atrribute object from my Entity.
public List<T> findAll() {
this.entityManager = SingletonEntityManagerFactory.get().createEntityManager();
EntityTransaction tx = this.entityManager.getTransaction();
try {
tx.begin();
return this.entityManager.createQuery(
"select f from " + clazz.getName() + " as f").getResultList();
}finally {
tx.commit();
if (tx.isActive()) {
tx.rollback();
}
this.entityManager.close();
}
}
for instance, supposing T has a property of class A that is already an Entity persisted, i can't get A after having List
But i don't have this problem if I only look for a single Entity by Id. I obtain my entity and I can ask without problems for its attribute objects already persisted
public T getById(final Key id) {
return getEntityManager().find(clazz, id);
}
now i can do
A a= t.getA();
How can I write my implementation of findAll() avoiding this error? maybe another Component instead of EntityManager? How can i make it generic, and not having to implement specific code for specific type of entities?
What you do there doesn't make sure the field is loaded before leaving that method, so either access it, or make sure it is fetched by default.
Hi I am beginner on the JPA world, I have a question on the auto-generated id. We are using OpenJPA, My application requires that one operation which creates bunch of related objects must be inside a single transaction which will be part of global transaction (XA). I am struggling in get the auto-generated id and use it to set values in other object. Here is the snapshot:
#ENTITY
#Table(name="TDepart")
class Department{
private long id;
#GeneratedValue(strategy= GenerationType.TABLE)
public long getId();
}
//And some classes like
class Professor {
void setDepartmentId(long id);
}
Now I have a business operation:
void doSomething()
{
Department depart = new Department();
handleProfessors (depart);
handleStudent (depart);
//and someother rountines need to refer department
}
//sample code which will getId
void handleProfessors(Department depart)
{
Professor p = new Professor ();
p.setDepartmentId(depart.getId);
}
So the Department.getId() will be called several times. The doSomething() will be in a single managed transaction, but the GeneratedValue will use an unmanaged tx. Now may problem is: whenever the getId is called, it will return a new value, and when the department is final persisted, the id is the latest number, so all other objects refer to an non-exists department. Is there anyway to handle this so that the id is (kindof) persist?
I have a loose requirement solution, which will create an dummy department first and persist it, so the ID is not change. The code is similar to this:
void doSomething()
{
Department depart = createEmptyDepartment(); // always new tx so department is created;
try {
reallyDoSomehing(); // tx required so it is part of global tx
}
catch (SomeException e) {
removeEmptyDepartment(depart);
}
Now I do not know how I can set the tx for removeEmptyDepartment(), if is required it will use the global request so it will be rollback as well. If it is new tx it will cause a deadlock since reallyDoSomething() will lock the db row.
Please, give me some ideas on how to solve it.
Thanks,
Howard.
I don't fully understand your issue, but I'm thinking that rather than setting the departmentId in your professor class, you should be setting the Department instead
i.e.
void setDepartmentId(long id);
change to
void setDepartment(Department d);
The id components should be handled automatically by the entity manager
Hello everyone here is my DAO class :
public class UsersDAO extends HibernateDaoSupport {
private static final Log log = LogFactory.getLog(UsersDAO.class);
protected void initDao() {
//do nothing
}
public void save(User transientInstance) {
log.debug("saving Users instance");
try {
getHibernateTemplate().saveOrUpdate(transientInstance);
log.debug("save successful");
} catch (RuntimeException re) {
log.error("save failed", re);
throw re;
}
}
public void update(User transientInstance) {
log.debug("updating User instance");
try {
getHibernateTemplate().update(transientInstance);
log.debug("update successful");
} catch (RuntimeException re) {
log.error("update failed", re);
throw re;
}
}
public void delete(User persistentInstance) {
log.debug("deleting Users instance");
try {
getHibernateTemplate().delete(persistentInstance);
log.debug("delete successful");
} catch (RuntimeException re) {
log.error("delete failed", re);
throw re;
}
}
public User findById( java.lang.Integer id) {
log.debug("getting Users instance with id: " + id);
try {
User instance = (User) getHibernateTemplate()
.get("project.hibernate.Users", id);
return instance;
} catch (RuntimeException re) {
log.error("get failed", re);
throw re;
}
}
}
Now I wrote a test class(not a junit test) to test is everything working, my user has these fields in the database : userID which is 5characters long string and unique/primary key, and fields such as address, dob etc(total 15 columns in database table). Now in my test class I intanciated User added the values like :
User user = new User;
user.setAddress("some address");
and so I did for all 15 fields, than at the end of assigning data to User object I called in DAO to save that to database UsersDao.save(user); and save works just perfectly. My question is how do I update/delete users using the same logic?
Fox example I tried this(to delete user from table users):
User user = new User;
user.setUserID("1s54f"); // which is unique key for users no two keys are the same
UsersDao.delete(user);
I wanted to delete user with this key but its obviously different can someone explain please how to do these. thank you
UPDATE :
Do I need to set all 15 fields on User object to delete it like I did with save method ?
Having not looked at Hibernate for quite a while now, I can only hazard a guess at the problem.
It seems that you are creating a User object, but only populating the User ID field, so the persistence layer knows nothing about the actual User.
I would recommend using a retrieve function that can find the User with the given ID, and then pass that User into the delete method.
User u = UsersDao.findById("1s54f");
UsersDao.delete(u);
This should work, as the persistence layer will know about the User, so it has all of the details it needs to perform the delete.
However, a more efficient method would be to find a way of deleting a user by ID, so you do not have to query the database to get the instance of the User and then delete it.
Hope this helps.
Chris
In an ideal world you will have your model's business key as the database primary key and you'll not have this problem. But it ain't so, isn't it?
For you particular problem if you are very much sure that the userID is going to be unique then you can try this (taken from here):
Session session = sessionFactory.openSession();
Transaction tx = session.beginTransaction();
String hqlDelete = "delete User u where u.userID = :id";
int deletedEntities = s.createQuery( hqlDelete )
.setString( "id", userID )
.executeUpdate();
tx.commit();
session.close();
But let me warn you. This kind of code is not good at all. For example what happens if you decide in future that the column you used in delete is no longer unique? Then you'll run into a very serious bug or a very bad case of refactoring. Either way the fool-proof (may not be efficient & may not be feasible) way is to delete records based on their primary key.
Check out the documentation. Get used to the concept of persistent, transient, and detached instances. To delete an instance, you call
session.delete(persistentInstance)
and to update (although you probably shouldn't need to use it), call
persistentInstance = session.merge(detachedInstance)
Shouldn't need to use update? No, because you just need to load/find an object first, and then modify it. Any modifications you make to a persistent object will automatically be saved back to the database.
In order to delete the user that its ID is "1s54f" you should create a delete HQL as follows:
public void delete(String id) {
log.debug("deleting Users instance");
try {
final String deleteQuery = "delete from User where id = :id";
final Query query = getSession().createQuery(deleteQuery);
final query.setString("id",id);
final int rowCount = query.executeUpdate(); // check that the rowCount is 1
log.debug("delete successful");
} catch (RuntimeException re) {
log.error("delete failed", re);
throw re;
}
}
Then you can use this method like:
userDao.delete("1s54f");
Hope this helps.
Hibernate is an object-relational mapper, that is, it translates between the world of relational databases and object-oriented Java code. Since primary keys are a database concept, it is hibernate's job to translate them into object-oriented terms (in this case: object identity).
That is, if you pass primary keys to hibernate, you are not using hibernate as intended; calling code should represent persistent data with mapped objects, not primary keys. This also allows hibernate to automatically guard against lost updates by checking version numbers.
The typical pattern therefore is to have the following signature:
interface UserDAO {
void delete(User user);
}
and require the DAOs caller to come up with a persistent object to pass to it. The caller might have such an object lying about from the current or a previous (now closed) session, after all, he did somehow learn about its primary key. If all else fails, you can use session.load(User.class, id) to ask hibernate for a proxy to pass to the delete method. (Note that one shouldn't use session.load if the object might no longer exist in the database.)
It's not necessary fetch a whole entity before removing it, neither create a hardcoded query for delete, nor setting every field in entity.
Maybe better way to do that is setting the id for entity and use Hibernate API itself.
If a specific dao is used to entity User, as described in question, try:
public void remove(Serializable id) throws InstantiationException, IllegalAccessException {
User user = new User();
getSessionFactory().getClassMetadata(getEntityClass()).setIdentifier(user, id, (SessionImplementor) getSessionFactory().getCurrentSession());
getHibernateTemplate().delete(entity);
}
As can be seen, neither unnecessary operation in database is made.
And this can be used in generic flavor if GenericDao is implemented like:
public void remove(Serializable id) throws InstantiationException, IllegalAccessException {
Model entity = entityClass.newInstance();
getSessionFactory().getClassMetadata(getEntityClass()).setIdentifier(entity, id, (SessionImplementor) getSessionFactory().getCurrentSession());
getHibernateTemplate().delete(entity);
}
Both ways, Dao must extend org.springframework.orm.hibernate4.support.HibernateDaoSupport to get advantages.
Here's a fragment of generic:
public class GenericDaoImpl<Model> extends HibernateDaoSupport implements GenericDao<Model> {
private Class<Model> entityClass;
public GenericDaoImpl() {
this.entityClass = (Class<Model>) ((ParameterizedType) getClass().getGenericSuperclass()).getActualTypeArguments()[0];
}
/* CRUD are implemented here */
public void remove(Serializable id) throws InstantiationException, IllegalAccessException {
Model entity = entityClass.newInstance();
getSessionFactory().getClassMetadata(getEntityClass()).setIdentifier(entity, id, (SessionImplementor) getSessionFactory().getCurrentSession());
getHibernateTemplate().delete(entity);
}
}