Can't create EntityManager using JTA Datasource - jpa

Question

I'm trying to instantiate an EntityManager using a JTA Datasource, but I always get NullPointerException.
Here's my environment:
Server : JBossAS 7.0
JPA : 2.0
DB : MySQL
persistence.xml
<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.0" 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_2_0.xsd">
<persistence-unit name="WebStock" transaction-type="JTA">
<provider>org.hibernate.ejb.HibernatePersistence</provider>
<jta-data-source>stockmanagementDS</jta-data-source>
<class>prv.stockmanagement.business.Product</class>
</persistence-unit>
</persistence>
On a dao class I'm trying this :
#PersistenceContext(type=PersistenceContextType.EXTENDED, unitName="WebStock")
private EntityManager em;
but when I use its getter, I get NullPointerException here :
public EntityManager getEntityManager() {
return em;
}
the debug shows it's null.
Here's the datasource definition in the standalone.xml :
<datasource jndi-name="stockmanagementDS" pool-name="stockmanagement" enabled="true" jta="true" use-java-context="true" use-ccm="true">
<connection-url>
jdbc:mysql://localhost:3306/kitchen_stock
</connection-url>
<driver>
mysql
</driver>
<security>
<user-name>
root
</user-name>
<password>
rootroot
</password>
</security>
<statement>
<prepared-statement-cache-size>
100
</prepared-statement-cache-size>
<share-prepared-statements/>
</statement>
</datasource>
"mysql" is the name of the driver I defined after the datasource :
<drivers>
<driver name="mysql" module="com.sql.mysql">
<driver-class>
com.mysql.jdbc.Driver
</driver-class>
</driver>
<driver name="h2" module="com.h2database.h2">
<xa-datasource-class>
org.h2.jdbcx.JdbcDataSource
</xa-datasource-class>
</driver>
</drivers>
Persistence is under META-INF, it's dynamic web project, and it's working well. The classing using the entity manager is not an EJB.
Any hint?

Answer 1

Let me draw your attention to the following moments:
1. I don't see in your code driver for MySql to which you refer from datasource:
<driver>
mysql
</driver>
You mast do follow:
Enter in the file path ${jboss_home}/modules and create the directories com/mysql/jdbc/main. Into the folder main copy the driver library jar (for example mysql-connector-java-5.1.38-bin.jar) and create a file module.xml:
<?xml version="1.0" encoding="UTF-8"?>
<module xmlns="urn:jboss:module:1.0" name="com.mysql.jdbc">
<resources>
<resource-root path="mysql-connector-java-5.1.38-bin.jar"/>
</resources>
<dependencies>
<module name="javax.api"/>
</dependencies>
</module>
And to the <drivers> tag in the standalone.xml add:
<driver name="mysql" module="com.mysql.jdbc">
<xa-datasource-class>com.mysql.jdbc.jdbc2.optional.MysqlXADataSource</xa-datasource-class>
</driver>
2. May be you should put your persistence.xml in your web module:
web
src
main
java
..
resources
META-INF
persistence.xml
webapp
..
3. You can do inject EntiryManeger only into EJB or class with #Transactional annotation. Check to be sure your DAO class it is EJB bean.