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From "Phani Madgula" <phanibalaji.madg...@gmail.com>
Subject Re: JPA, entities and EJB3
Date Tue, 10 Jun 2008 09:40:35 GMT
Here is what I observed.

1. If @PersistenceContext(unitName="Tutorial") is used, irrespective of
"transaction-type" (JTA or RESOURCE_LOCAL) the ContainerManaged EM is
returned. UserTransaction object should be used to perform transactions.
Because, if EntityTransaction object is used, the server throws exception.
The persistence context is carried over by JTA transaction during the life
of the transaction. In this case, if the value "RESOURCE_LOCAL" is used for
"transaction-type" the commits will not happen. I think the value "JTA" for
transaction-type attribute only makes sense??

2. if @PeristenceUnit(unitName="Tutorial") is used and the value of
transaction-type is RESOURCE_LOCAL, whenever EM is obtained from EMF, a new
persistence context is returned. EntityTransaction object should be used to
perform transactions. Using UserTransaction Object does not commit the
values.

3. if @PeristenceUnit(unitName="Tutorial") is used and the value of
transaction-type is JTA, whenever EM is obtained from EMF, a new persistence
context is returned. EntityTransaction object can not be used. The server
throws exception. Only UserTransaction object can be used. Even though, a
new PeristenceContext is obtained every time EM is got from the EMF, the
last update made to an entity (irrespective of which PersistenceContext made
the update) is committed to the database.

I am confused as to where the above scenarios come into play in real world
applications. But I do understand ContainerManaged EM + JTA and
ApplicationManaged EM + RESOURCE_LOCAL combinations. Request clarification
on other combinations??

Thanks
Phani



On Tue, Jun 10, 2008 at 9:23 AM, Phani Madgula <
phanibalaji.madgula@gmail.com> wrote:

> Thanks for the info. I looked into Spec and got a very vague idea of what's
> happening here. Let me test these scenarios with some samples and understand
> what's happening.
>
> Thanks
> Phani
>
>
> On Mon, Jun 9, 2008 at 11:35 PM, David Jencks <david_jencks@yahoo.com>
> wrote:
>
>> I looked in the spec a bit and am not sure I understand how all the parts
>> are meshing, maybe david blevins can chime in...   I think that you've
>> specified contradictory information and maybe we should be complaining
>> rather than supplying a container managed jta EntityManager.
>> I _think_ that your annotation-injected EntityManager has to be container
>> managed and hence jta.
>> I _think_ that if you want a resource-local EntityManager you have to
>> inject the EMF with a PersistenceUnit annotation and get the EntityManager
>> yourself.
>>
>> In the spec, section 5.6 starts:
>> Whenacontainer-managedentitymanager isused, thelifecycleof
>> thepersistencecontext isalways
>> managedautomatically, transparentlytotheapplication,
>> andthepersistencecontextispropagatedwith
>> the JTA transaction.
>>
>>
>> I think this means that with your @PersistenceContext annotation, you are
>> definitely going to get a tx-type=JTA EM.  Since you specified
>> RESOURCE_LOCAL in the persistence.xml I think we should perhaps be
>> objecting.
>>
>> I also think this means that you need an application managed persistence
>> context to get RESOURCE_LOCAL.  There are a bunch of examples in section 5.7
>> that all use @PersistenceUnit.
>>
>> Also hoping for clarification....
>> david jencks
>>
>> On Jun 9, 2008, at 1:43 AM, Phani Madgula wrote:
>>
>> Hi,
>> I have tried to play with <jta-datasource> and <non-jta-datasource> as
>> follows.
>>
>> I have the following peristence.xml in a web application.
>> ***********
>> <?xml version="1.0" encoding="UTF-8" ?>
>> <persistence xmlns="http://java.sun.com/xml/ns/persistence"
>>    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
>>    xsi:schemaLocation="http://java.sun.com/xml/ns/persistence
>> http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd"
>> version="1.0">
>>
>>    <!-- Tutorial "unit" -->
>>    <persistence-unit name="Tutorial" transaction-type="RESOURCE_LOCAL">
>>
>>    <provider>org.apache.openjpa.persistence.PersistenceProviderImpl</provider>
>>    <non-jta-data-source>ProductDS-nonJTA</non-jta-data-source>
>>    <mapping-file>orm.xml</mapping-file>
>>    <class>samples.jpa.Product</class>
>>    <class>samples.jpa.Book</class>
>>
>>    </persistence-unit>
>>
>> </persistence>
>>
>> ***********
>>
>> In the servlet, I have the following code
>>
>> ***********
>> @PersistenceContext(unitName="Tutorial")
>>   private EntityManager em;
>> .....
>> ....
>>  UserTransaction ut;
>>  try{
>>  Context ctx = new InitialContext();
>>
>>  //ut = (UserTransaction)ctx.lookup("java:comp/UserTransaction");
>>   //ut.begin();
>>
>>   //EntityTransaction et = em.getTransaction();
>>  //et.begin();
>>
>>  Book book = new Book("DDDDD","John",1.0,"Joe","1934834-23823","Phani");
>>   em.persist(book);
>>
>>  //et.commit();
>>   //ut.commit();
>>
>>  }catch(Exception e){
>>  e.printStackTrace();
>>   throw new ServletException (e);
>>  }
>> ***********************
>>
>> 1. When I hit the servlet, I get the following error.
>>
>>   ***********************
>>   javax.persistence.TransactionRequiredException : No Active transaction
>>   ***********************
>>
>> 2. Suppose I have the following code in the servlet
>>    **********************
>> ***********
>> @PersistenceContext(unitName="Tutorial")
>>   private EntityManager em;
>> .....
>> ....
>>  UserTransaction ut;
>>  try{
>>  Context ctx = new InitialContext();
>>
>>  //ut = (UserTransaction)ctx.lookup("java:comp/UserTransaction");
>>   //ut.begin();
>>
>> //Uncomment EntityTransaction
>>  EntityTransaction et = em.getTransaction();
>>  et.begin();
>>
>>  Book book = new Book("DDDDD","John",1.0,"Joe","1934834-23823","Phani");
>>   em.persist(book);
>>
>>         et.commit();
>>   //ut.commit();
>>
>>  }catch(Exception e){
>>  e.printStackTrace();
>>   throw new ServletException (e);
>>  }
>>  ***********************
>>  I get the following error
>>  ***********************
>>
>>  java.lang.IllegalStateException : You can not call getTransaction on
>> a container managed EntityManager
>>
>>  *************************
>>
>> 3. Only if I use JTA API, I am able to get the entity persisted
>> properly as below.
>> ***************************
>> @PersistenceContext(unitName="Tutorial")
>>   private EntityManager em;
>> .....
>> ....
>>  UserTransaction ut;
>>  try{
>>  Context ctx = new InitialContext();
>>
>>  ut = (UserTransaction)ctx.lookup("java:comp/UserTransaction");
>>   ut.begin();
>>
>>
>>  Book book = new Book("DDDDD","John",1.0,"Joe","1934834-23823","Phani");
>>   em.persist(book);
>>
>>
>>  ut.commit();
>>
>>  }catch(Exception e){
>>   e.printStackTrace();
>>  throw new ServletException (e);
>>  }
>> ****************************
>>
>> Please note that I am using "RESOURCE_LOCAL" persistence unit. I also
>> used <non-jta-datasource>. I deployed the database pool with
>> </no-transaction> tag in the connector deployment plan.
>>
>> My questions are
>>
>> 1. Should we always use UserTransaction object irrespective of
>> <jta-datasource> or <non-jta-datasource> in JEE environment??
>>
>> 2. How is the use of <non-jta-datsource> different from the use
>> <jta-datasource> in JEE environment??
>>
>> 3. In EJBs, when ContainerManaged Transactions are used, there is no
>> need to use JTA. Is that correct??
>>
>> 4. Only in J2SE environments, we can use EntityTransaction object. is
>> that correct??
>>
>> Thanks in advance.
>> Phani
>>
>> On 5/28/08, David Jencks <david_jencks@yahoo.com> wrote:
>>
>> 1. I hope you named the file openejb-jar.xml
>>
>> 2. jta-datasource and non-jta-datasource have to contain the names of
>>
>> the datasources in the geronimo plan used for the pool, NOT some jndi
>>
>> name you might also map them to.  The datasources don't need to be
>>
>> bound in jndi in order to be used for jpa
>>
>> 3. The non-jta-datasource must be a datasource that really has no
>>
>> transaction support, using the <no-transaction/> element instead of
>>
>> <local-transaction/> or <xa-transaction>... in the connector plan.
>>
>> With derby I find it necessary to have a non-jta-datasource if any ddl
>>
>> is needed or if openjpa is generating the primary keys.  I don't know
>>
>> if you can get away without one for other databases.  If you want to
>>
>> experiment, leave out the non-jta-datasource rather than duplicating
>>
>> the jta-datasource contents.
>>
>>
>> hope this helps
>>
>> david jencks
>>
>>
>> On May 27, 2008, at 4:09 PM, zeros wrote:
>>
>>
>>
>> Good evening:
>>
>>
>>   I'm newbie with EJB3.0. I want to configure the persistence.xml
>>
>> to have
>>
>> entities managed with JPA. I have the next configuration files:
>>
>> OPENJPA-JAR.XML
>>
>>
>> <openejb-jar xmlns="http://www.openejb.org/xml/ns/openejb-jar-2.1"
>>
>> xmlns:nam="http://geronimo.apache.org/xml/ns/naming-1.1"
>>
>> xmlns:pkgen="http://www.openejb.org/xml/ns/pkgen-2.0"
>>
>> xmlns:sec="http://geronimo.apache.org/xml/ns/security-1.1"
>>
>> xmlns:sys="http://geronimo.apache.org/xml/ns/deployment-1.2">
>>
>> <sys:environment>
>>
>>   <sys:moduleId>
>>
>>      <sys:groupId>o2o.marketing</sys:groupId>
>>
>>     <sys:artifactId>EJB</sys:artifactId>
>>
>>     <sys:version>1.0.8</sys:version>
>>
>>     <sys:type>jar</sys:type>
>>
>>   </sys:moduleId>
>>
>>   <sys:dependencies>
>>
>>        <sys:dependency>
>>
>>           <sys:groupId>console.dbpool</sys:groupId>
>>
>>        <sys:artifactId>marketing</sys:artifactId>
>>
>>         <sys:version>1.0</sys:version>
>>
>>          <sys:type>rar</sys:type>
>>
>>  </sys:dependency>
>>
>>  </sys:dependencies>
>>
>> </sys:environment>
>>
>> </openejb-jar>
>>
>>
>> And I have also persistence.xml
>>
>>
>> <?xml version="1.0" encoding="UTF-8"?>
>>
>> <persistence version="1.0" xmlns="http://java.sun.com/xml/ns/persistence
>>
>> "
>>
>> xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
>>
>> xsi:schemaLocation="http://java.sun.com/xml/ns/persistence
>>
>> http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd">
>>
>> <persistence-unit name="marketing">
>>
>>    <description>Entity Beans for User</description>
>>
>>
>> <provider>org.apache.openjpa.persistence.PersistenceProviderImpl</
>>
>> provider>
>>
>>    <jta-data-source>java:comp/env/marketing</jta-data-source>
>>
>>    <non-jta-data-source>java:comp/env/marketing</non-jta-data-source>
>>
>>        <mapping-file>META-INF/orm.xml</mapping-file>
>>
>>       <properties />
>>
>> </persistence-unit>
>>
>> </persistence>
>>
>>
>> The error which I'm having is the next one: Unable to resolve
>>
>> reference
>>
>> "JtaDataSourceWrapper" and Unable to resolve reference
>>
>> "NonJtaDataSourceWrapper", which are basically the same error.
>>
>>
>> I think this is produced because I'm not mapping the Datasocurce to
>>
>> the
>>
>> DBPool. Geronimo returns to me examples to do it for web, but no
>>
>> example to
>>
>> do it for an EJB.
>>
>>
>> Please could you help me?
>>
>>
>> WATCH OUT! I'm talking about entities and EJB3.0, not entiti beans and
>>
>> EJB2.0
>>
>>
>> Thanks in advance
>>
>>
>> SERGIO
>>
>> --
>>
>> View this message in context:
>>
>>
>> http://www.nabble.com/JPA%2C-entities-and-EJB3-tp17502079s134p17502079.html
>>
>> Sent from the Apache Geronimo - Users mailing list archive at
>>
>> Nabble.com.
>>
>>
>>
>>
>>
>>
>

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