I have an application which has a table and when you click on an item in the table it fills in a group of textfields with its data (FieldGroup), and then you have the option of saving the changes I was wondering how would I save the changes the user makes to my postgres database. I am using vaadin and hibernate for this application. So far I have tried to do
editorField.commit() // after the user clicks the save button
I have tried
editorField.commit()
hbsession.persist(editorField) //hbsession is the name of my Session
and I have also tried
editorField.commit();
hbsession.save(editorField);
The last two ones give me the following error
Caused by: org.hibernate.SessionException: Session is closed!
Well, the first thing you need to realize is Vaadin differs from conventional request/response web framework. Actually, Vaadin is *event driven* framework very similar to Swing. It builds a application context from very first click of the user and holds it during whole website visit. The problem is there is no entry request point you can start hibernate session and no response point to close. There are tons of requests during a single click on button.
So, entitymanager-per-request pattern is completely useless. It is better to use one standalone em or em-per-session pattern with hibernate.connection_release after_transaction to keep connection pool low.
To the JPAContianer, it is not usable as far you need to refresh the container or you have to handle beans with relations. Also, I did not manage to get it working with batch load, so every reading of entry or relation equals one select to DB. Do not support lazy loading.
All you need is open EM/session. Try to use suggested patters or open EM/session every transaction and merge your bean first.
Your question is quite complex and hard to answer, but I hope these links help you get into:
Pojo binding strategy for hibernate
https://vaadin.com/forum#!/thread/39712
MVP-lite
https://vaadin.com/directory#addon/mvp-lite (stick with event driven pattern)
I have figured out how to make changes to the database here is some code to demonstrate:
try {
/** define the session and begin it **/
hbsession = HibernateUtil.getSessionFactory().getCurrentSession();
hbsession.beginTransaction();
/** table is the name of the Bean class linked to the corresponding SQL table **/
String query = "UPDATE table SET name = " + textfield.getValue();
/** Run the string as an SQL query **/
Query q = hbsession.createQuery(query);
q.executeUpdate(); /** This command saves changes or deletes a entry in table **/
hbsession.getTransaction().commit();
} catch (RuntimeException rex) {
hbsession.getTransaction().rollback();
throw rex;
}
Related
I've been struggling for few hours with this one and could do with some help.
A client sends an object that contains a list;
One of the objects in the list has been modified on the client;
In some cases I don't want that modified entity to be persisted to the database, I want to keep the original database values.
I have tried the following and various attempts to clear(), refresh() and flush() the session:
List<Integer> notToModifyIds = dao.getDoNotModifyIds(parentEntity.getId());
MyEntityFromList entityFromClient, entityFromDb;
for(Integer notToModifyId : notToModifyIds){
ListIterator iterator = parentEntity.getEntities().listIterator();
while(iterator.hasNext()){
entityFromClient = (MyEntity) iterator.next();
if(Objects.equals(entityFromClient.getId(), notToModifyId)){
dao.evict(entityFromClient);
entityFromDb = (MyEntity) dao.get(MyEntity.class, notToModifyId);
iterator.remove(entityFromClient);
iterator.add(entityFromDb);
}
}
}
However, no matter what I try I always get the values from the client persisted to the database. When I add a breakpoint after iterator.add() I can check that the database value has not been updated at that point, hence I know that if I could load the entity from the DB then I would have the value I want.
I'm feeling a little suppid!
I don't know if I got the whole scenario here. Are those modified "entitiesFromClient" attached to the Hibernate session? If they are, the changes were probably automatically flushed to the database before you "evicted" them.
Setting a MANUAL flush mode would help you avoid the automatic behaviour.
First of all, I would enable the Hibernate SQL logging to see more precisely what is happening. See Enable Hibernate logging.
Checking the database in another session (while stopped in the breakpoint) will not help if this code is running within a transaction. Even if the change was already flushed in the database you wouldn't see it until the transaction is commited.
I have a hibernate query (hibernate 3) that only reads data from the database. The database is updated by a separate application and the query result does not reflect the changes in the database.
With a bit of research, I think it may have something to do with the Hibernate L2 cache (I don't think it's the L1 cache since I always open a new session and close it after it's done).
Session session = sessionFactoryWrapper.getSession();
List<FlowCount> result = session.createSQLQuery(flowCountSQL).list();
session.close();
I tried disabling the second-layer cache in the hibernate config file but it's not working:
<property name="hibernate.cache.use_second_level_cache">false</property>
<property name="hibernate.cache.use_query_cache">false</property>
<propertyname="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>
I also added session.setCacheMode(CacheMode.Refresh); after Session session = sessionFactoryWrapper.getSession(); to force a refresh on the L1 cache but still not working...
Is there another way to pick up the changes in the database? Am I doing something wrong on how to disable the cache? Thanks.
Update:
I did another experiment by monitoring the database query log:
Run the code the 1st time. Check the log. The query shows up.
Wait a few minutes. The data has changed by another application. I verified it through MySql Workbench. To distinguish from the previous query I add a dummy condition.
Run the code the 2nd time. Check the log and the query shows up.
Both time I'm using the same query but since the data has changed, the result should be different but somehow it's not...
In order to force a L1 cache refresh you can use the refresh(Object) method of Session.
From the Hibernate Docs,
Re-read the state of the given instance from the underlying database.
It is inadvisable to use this to implement long-running sessions that
span many business tasks. This method is, however, useful in certain
special circumstances. For example
where a database trigger alters the object state upon insert or update
after executing direct SQL (eg. a mass update) in the same session
after inserting a Blob or Clob
Moreover you mentioned that you added session.setCacheMode(CacheMode.Refresh) to force a refresh on the L1 cache. This won't work because, CacheMode doesn't have to do anything with L1 cache. From the Hibernate Docs again,
CacheMode controls how the session interacts with the second-level
cache and query cache.
Without second-level cache and query cache, hibernate will always fetch all data from database in a new session.
You can check which query exactly is executed by Hibernate by enabling DEBUG log level for org.hibernate package (and TRACE level for org.hibernate.type if you want to see bound variables).
How old of a change is the query reflecting? If it is showing the changes after sometime, it might have to do with how you obtain your session.
I am not familiar with the SessionFactoryWrapper class, is this a custom class that you wrote? Are you somehow caching the session object longer than it is necessary? If so, the query will be reusing the objects if it has already been loaded in the session. This is the idea behind the repeatable read semantics that Hibernate guarantees.
You can clear the session before running your query and it will then return the latest data.
Hibernate's built-in connection pooling mechanism is bugged.
Replace it with a production quality alternative like c3p0.
I had the exact same issue where stale data was returned until I started using c3p0.
Just in case it IS the 1st Level Cache
Can you show the query you make ?
See following Bugs:
https://hibernate.atlassian.net/browse/HHH-9367
https://jira.grails.org/browse/GRAILS-11645
Additional:
http://howtodoinjava.com/2013/07/01/understanding-hibernate-first-level-cache-with-example/
http://www.dineshonjava.com/p/cacheing-in-hibernate-first-level-and.html#.VhZ7o3VElhE
Repeatable finder problem caused by Hibernates 1st Level Cache
To be clear, both test succeed - not logically at all:
userByEmail('foo#bar.com').email != 'foo#bar.com'
Complete Test
#Issue('https://jira.grails.org/browse/GRAILS-11645')
class FirstLevelCacheSpec extends IntegrationSpec {
def sessionFactory
def setup() {
User.withNewSession {
User user = new User(email: 'test#test.org', password: 'test-password')
user.save(flush: true, failOnError: true)
}
}
private void updateObjectInNewSession(){
User.withNewSession {
def u = User.findByEmail('test#test.org', [cache: false])
u.email = 'foo#bar.com'
u.save(flush: true, failOnError: true)
}
}
private User userByEmail(String email){
User.findByEmail(email, [cache: false])
}
def "test first update"() {
when: 'changing the object in another session'
updateObjectInNewSession()
then: 'retrieving the object by changed identifier (no 2nd level cache)'
userByEmail('foo#bar.com').email == 'foo#bar.com'
}
def "test stale object in 1st level"() {
when: 'changing the object after pulling objects to cache by finder'
userByEmail('test#test.org')
updateObjectInNewSession()
then: 'retrieving the object by changed identifier (no 2nd level cache)'
userByEmail('foo#bar.com').email != 'foo#bar.com'
}
}
I'm writing a project for college and I've encountered some strange phenomena.
The program supposed to serve a restaurant so it has a server side that manages all the needs of the different front ends. the different front ends are "dinner terminal", "kitchen terminal", "waiter terminal" and an "admin terminal".
When I add an object to the DB I see it in the DB and the kitchen terminal receives it and I see that the object it gets is the right one.
public void addSessionOrder(String id, SessionOrder sessionOrder)
{
Session context = clientSessions.get(id);
context.beginTransaction();
context.save(sessionOrder);
context.getTransaction()
.commit();
}
notice that each terminal (connection) has it's own session in hibernate.
however, once I try to update the status of a sessionorder i get this exception
java.lang.NullPointerException
at database.DatabaseContext.updateSessionOrderStatus(DatabaseContext.java:170)
at protocol.handlers.UpdateSessionOrderStatusHandler.handle(UpdateSessionOrderStatusHandler.java:35)
at server.ResturantServer.handleClientMessage(ResturantServer.java:126)
at server.ConnectionManager.handleClientMessage(ConnectionManager.java:86)
at server.SockJSSocketHandler$3.handle(SockJSSocketHandler.java:55)
this is the method:
public void updateSessionOrderStatus(String id, SessionOrder order, OrderStatus newStatus)
{
Session context = clientSessions.get(id);
context.beginTransaction();
SessionOrder ord = (SessionOrder)context.get(SessionOrder.class, order.getOrderId());
ord.setStatus(newStatus);
context.update(ord);
context.getTransaction()
.commit();
}
The line that throws the exception is "ord.setStatus(newStatus);"
after debugging this is the info I have:
fields id and sessionOrder contain legit data and are initiated as needed.
sessionOrder.getOrderId() returns the needed ID for a corresponding object in the DB (it exists)
the query on the DB return null to ord.
Another thing I've noticed, if I turn the server off (kill hibernate) and restart everything, the whole things works fine. So I believe it has something to do with the fact that some session X inserted the object to the DB, and some other session Y tries to retrieve it afterwards.
the sessions are different and originate from different connections, and the specific order exists in the DB so I see no reason for it not to return the value.
I think it has something to do with caching of the model, however I'm quite a noob in hibernate so I can't pin point the problem.
sessionOrder.getOrderId() returns the needed ID for a corresponding object in the DB (it exists) the query on the DB return null to ord.
The ord object is null so it throws a NPE. I guess that hibernate cannot find the order with the given ID.
Add some logging here and you'll see what causes you trouble
I have a web application build in Django + Python that interact with web services (written in JAVA).
Now all the database management part is done by web-services i.e. all CRUD operations to actual database is done by web-services.
Now i have to track all User Activities done on my website in some log table.
Like If User posted a new article, then a new row is created into Articles table by web-services and side by side, i need to add a new row into log table , something like "User : Raman has posted a new article (with ID, title etc)"
I have to do this for all Objects in my database like "Article", "Media", "Comments" etc
Note : I am using PostgreSQL
So what is the best way to achieve this..?? (Should I do it in PostgreSQL OR JAVA ..??..And How..??)
So, you have UI <-> Web Services <-> DB
Since the web services talk to the DB, and the web services contain the business logic (i.e. I guess you validate stuff there, create your queries and execute them), then the best place to 'log' activities is in the services themselves.
IMO, logging PostgreSQL transactions is a different thing. It's not the same as logging 'user activities' anymore.
EDIT: This still means you create DB schema for 'logs' and write them to DB.
Second EDIT: Catching log worthy events in the UI and then logging them from there might not be the best idea either. You will have to rewrite logging if you ever decide to replace the UI, or for example, write an alternate UI for, say mobile devices, or something else.
For an audit table within the DB itself, have a look at the PL/pgSQL Trigger Audit Example
This logs every INSERT, UPDATE, DELETE into another table.
In your log table you can have various columns, including:
user_id (the user that did the action)
activity_type (the type of activity, such as view or commented_on)
object_id (the actual object that it concerns, such as the Article or Media)
object_type (the type of object; this can be used later, in combination with object_id to lookup the object in the database)
This way, you can keep track of all actions the users do. You'd need to update this table whenever something happens that you wish to track.
Whenever we had to do this, we overrode signals for every model and possible action.
https://docs.djangoproject.com/en/dev/topics/signals/
You can have the signal do whatever you want, from injecting some HTML into the page, to making an entry in the database. They're an excellent tool to learn to use.
I used django-audit-log and I am very satisfied.
Django-audit-log can track multiple models each in it's own additional table. All of these tables are pretty unified, so it should be fairly straightforward to create a SQL view that shows data for all models.
Here is what I've done to track a single model ("Pauza"):
class Pauza(models.Model):
started = models.TimeField(null=True, blank=False)
ended = models.TimeField(null=True, blank=True)
#... more fields ...
audit_log = AuditLog()
If you want changes to show in Django Admin, you can create an unmanaged model (but this is by no means required):
class PauzaAction(models.Model):
started = models.TimeField(null=True, blank=True)
ended = models.TimeField(null=True, blank=True)
#... more fields ...
# fields added by Audit Trail:
action_id = models.PositiveIntegerField(primary_key=True, default=1, blank=True)
action_user = models.ForeignKey(User, null=True, blank=True)
action_date = models.DateTimeField(null=True, blank=True)
action_type = models.CharField(max_length=31, choices=(('I', 'create'), ('U', 'update'), ('D', 'delete'),), null=True, blank=True)
pauza = models.ForeignKey(Pauza, db_column='id', on_delete=models.DO_NOTHING, default=0, null=True, blank=True)
class Meta:
db_table = 'testapp_pauzaauditlogentry'
managed = False
app_label = 'testapp'
Table testapp_pauzaauditlogentry is automatically created by django-audit-log, this merely creates a model for displaying data from it.
It may be a good idea to throw in some rude tamper protection:
class PauzaAction(models.Model):
# ... all like above, plus:
def save(self, *args, **kwargs):
raise Exception('Permission Denied')
def delete(self, *args, **kwargs):
raise Exception('Permission Denied')
As I said, I imagine you could create a SQL view with the four action_ fields and an additional 'action_model' field that could contain varchar references to model itself (maybe just the original table name).
I'm having some trouble with EclipseLink. My program has to interact with a database (representing a building). I've written a little input-testmode where I can manually insert stuff through the console.
My problem: a normal getByID-operation works just fine if I try to retrieve an entity I previously inserted through EclipseLink itself (by commit()), but throws a NoResultException when trying to select a row manually inserted via SQL-script (building -> lots of rooms -> script).
This (oversemplified) works fine:
main() {
MyRoom r = new MyRoom();
r.setID("floor1-roomnr4");
em.commit(r); //entity manager
DAO.getRoomByID("floor1-roomnr4"); // works
}
and the combination of generation-script + simply getRoomByID() throws an exception.
If I try it in SQL Developer I get the result I want for the exact select statement which just threw a NoResultException. I also only get this problem in the input-mode, otherwise selecting the generated rows works also fine.
Does EclipseLink have some cache-mechanism I'm unaware of which is causing some problem?
Are you sure EclipseLink and SQL Developer are connected to the same Database? Please verify the connection information for both. Is the generation-script committing the changes with the "commit" command?
If EclipseLink works similarly to Hibernate then yes there is a cache. The "first level cache" guaranties that you get the exact same instance within one transaction which makes sense. If you know EclipseLink/transactions then try to evict all loaded instances or commit the transaction and then try your DAO again. This would force EclipseLink to fetch the data from the database again
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