Hi!!!

I need some help from Hibernate gurus. I'm not be able to understand completely the use of isolation levels in Hibernate. I try to expose my problem in a few lines.

I have 2 threads A and B, each of one with a different Session object. Both access to the same persisten data P, and execute the next operations:

A -> get session
A -> begin tx
B -> get session
B -> begin tx
B -> update(P)
B -> commit tx
B -> close session
A -> update(P)
A -> commit tx
A -> close session

I hope that in the 'commit' step, I acquired an exception because the B thread commit first the changes, but it could update the same data. With tradtional JDBC I'd obtained an exception.

How I can obtain the same result using Hibernate? Must I use version or timestamp columns or is enough setting the isolation level property in Hibernate configuration file?

For the using of Lock class, is it necessary add version/timestamp column?

I review for hours this forum, but I could resolve my dues. Below you can see my code.

Thanks in advance,

P.D. I sent this topic, by mistake, in another forum. I'm sorry






Hibernate version:2.1.6

Mapping documents:
<?xml version="1.0"?>

<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 2.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd">

<hibernate-mapping>
<class
name="com.bbvasuiza.titulares.persistence.vo.TitularVO"
table="DC_TITULARES"
dynamic-update="false"
dynamic-insert="false"
>

<id
name="id"
column="ID_TITULAR"
type="java.lang.Integer"
>
<generator class="identity">
</generator>
</id>

<property
name="annulationDate"
type="java.util.Date"
update="true"
insert="true"
access="property"
column="DATE_ANNUL"
/>

<property
name="birthdate"
type="java.sql.Date"
update="true"
insert="true"
access="property"
column="DATE_BIRTH"
/>

<property
name="businessPhone"
type="java.lang.String"
update="true"
insert="true"
access="property"
column="PH_BUSINESS"
/>

<property
name="cdNatures"
type="java.lang.String"
update="true"
insert="true"
access="property"
column="CDNATURES"
/>

<property
name="code"
type="java.lang.String"
update="true"
insert="true"
access="property"
column="CODE_TITUL"
/>

<property
name="codePoder"
type="java.lang.String"
update="true"
insert="true"
access="property"
column="CODE_PODER"
/>

<property
name="comments"
type="java.lang.String"
update="true"
insert="true"
access="property"
column="COMMENTS"
/>

<property
name="docId"
type="java.lang.String"
update="true"
insert="true"
access="property"
column="DOCID"
/>

<property
name="docIdEnd"
type="java.util.Date"
update="true"
insert="true"
access="property"
column="DOCIDEND"
/>

<property
name="docIdStart"
type="java.util.Date"
update="true"
insert="true"
access="property"
column="DOCIDSTART"
/>

<property
name="docNo"
type="java.lang.String"
update="true"
insert="true"
access="property"
column="DOCNO"
/>

<property
name="domicile"
type="java.lang.String"
update="true"
insert="true"
access="property"
column="DOMICILE"
/>

<property
name="domicileCountry"
type="java.lang.String"
update="true"
insert="true"
access="property"
column="DOM_COUNTR"
/>

<property
name="ebk"
type="java.lang.Boolean"
update="true"
insert="true"
access="property"
column="FLAG_EBK"
/>

<property
name="economyActivity"
type="java.lang.String"
update="true"
insert="true"
access="property"
column="ECOACTIV"
/>

<property
name="email"
type="java.lang.String"
update="true"
insert="true"
access="property"
column="EMAIL"
/>

<property
name="entryDate"
type="java.util.Date"
update="true"
insert="true"
access="property"
column="DATE_ENTRY"
/>

<property
name="fax"
type="java.lang.String"
update="true"
insert="true"
access="property"
column="FAX"
/>

<property
name="firstNationality"
type="java.lang.String"
update="true"
insert="true"
access="property"
column="NATIO"
/>

<property
name="homePhone"
type="java.lang.String"
update="true"
insert="true"
access="property"
column="PH_HOME"
/>

<property
name="idCLL"
type="java.lang.Integer"
update="true"
insert="true"
access="property"
column="IDCLL"
/>

<property
name="lastName"
type="java.lang.String"
update="true"
insert="true"
access="property"
column="LASTNAME"
/>

<property
name="mobilePhone"
type="java.lang.String"
update="true"
insert="true"
access="property"
column="PH_MOBILE"
/>

<property
name="modificationDate"
type="java.util.Date"
update="true"
insert="true"
access="property"
column="DATE_MOD"
/>

<property
name="origin"
type="java.lang.String"
update="true"
insert="true"
access="property"
column="ORIGIN"
/>

<property
name="personalId"
type="java.lang.Integer"
update="true"
insert="true"
access="property"
column="IDPERSL"
/>

<property
name="preName"
type="java.lang.String"
update="true"
insert="true"
access="property"
column="PRENAME"
/>

<property
name="residence"
type="java.lang.String"
update="true"
insert="true"
access="property"
column="RESIDENCE"
/>

<property
name="residenceCountry"
type="java.lang.String"
update="true"
insert="true"
access="property"
column="RES_COUNTR"
/>

<property
name="secondNationality"
type="java.lang.String"
update="true"
insert="true"
access="property"
column="NATIO2"
/>

<property
name="userMod"
type="java.lang.String"
update="true"
insert="true"
access="property"
column="USER_MOD"
/>

<property
name="web"
type="java.lang.Boolean"
update="true"
insert="true"
access="property"
column="WEB"
/>

<!--
To add non XDoclet property mappings, create a file named
hibernate-properties-TitularVO.xml
containing the additional properties and place it in your merge dir.
-->

</class>

</hibernate-mapping>



Name and version of the database you are using:SQL Server 2000 sp3



[/quote]

hi,
--> how?

you only need version to check if someone has updated the object before you

Ok, do you mean should I use optimistic locking I have to use a version/timestamp column? And, on the other hand, should I use pessimistic locking I have to set locks explicitly using the Lock class o lock() method?

Another question, when I don't use pessimistic locks nor version/timestamp column, what kind of isolation applies? I understood that the default of the database. If so, I'm confused. SQL Server establishes READ COMMITTED as default, but my A thread can finish its tx although the B thread modify the record. Does not relie Hibernate over the tx manager of the database?

Thanks for your help,

Roque

you can get more info in the reference guide
http://www.hibernate.org/hib_docs/refer ... tions.html

in my opinion, you should always avoid pessimistic when you can...

I red this chapter several times, but I don't understand it well.
My case is the described in "Many sessions with automatic versioning". I'm creating a web application (without application server). When it is said "However, the same persistent instances are reused for each interaction with the database". It means that if you want to update the object with id "id", have you to load it before you can update it?
, or can you have a new created object (for example in a GUI) with the same id of the object you want to update and the execute session.update(guiObject)?

And please, could you respond my dues of the last message? I need your help.

Thanks,

Roque

I cotinue with my problem...

Can anybody show me a few lines of code in which is obtained a pessimistic lock for updating an object and after it is updated?
The main requirement is that the object come from a GUI application. This GUI creates the object and sends it to Hibernate. I need to update it in a pessimistic way (client requirements)


I need that code for my curent project, please.

Best regards,

Roque

get hibernate in action chapter 5
if you don't, i'll see if i can find time to help you tonight

Thanks Anthony.
I asked to my boss for this book, but now he's on holidays. He must to sign the order, so I must to wait

i'm back, if you really want to obtain a pessimistic lock, then you need to:
1- begin trans
2- obtain object : Cat cat = (Cat) session.get(Cat.class,id,LockMole.UPGRADE)
...
4- Commit

you can also use session.lock(cat,LockMole.UPGRADE)

Hello,

At the end, I understood my problem, indeed my two problems.

1.- I'm using SQL Server and therefore the doesn't work because SQL Server doesn't support the "select for update" sentence.

2.- Hibernate doesn't flush the "update" operations inmediately at least you configure it "ad hoc" or you invoke explicitly session.flush(). Due to this, the database never blocked my two concurrents tx.

Anyway, thanks a lot for your help.

Best regards,

Roque

HIbernate3 supports pessimistic locking in SQL server, using "with (updlock, rowlock)"