仍然得到的PersistenceException：沒有持久性提供的EntityManager

我得到這樣一個異常部署我的應用程序後：仍然得到的PersistenceException：沒有持久性提供的EntityManager

Caused by: javax.persistence.PersistenceException: No Persistence provider for EntityManager named JavaAcademyUnit 
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:85) 
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:54) 
    at com.bogdankobylinsky.javaacademy.dao.impl.jpa.UserJPADAO.<init>(UserJPADAO.java:13)

，從而未能在這條線：

private EntityManager em = Persistence.createEntityManagerFactory("JavaAcademyUnit").createEntityManager();

JPA配置描述符persistance.xml文件位於正確的地方：./WEB-INF/classes/META-INF/persistence.xml幷包含：

<persistence xmlns="http://java.sun.com/xml/ns/persistence" version="2.0"> 
    <persistence-unit name="JavaAcademyUnit" transaction-type="JTA"> 
     <provider>org.hibernate.jpa.HibernatePersistenceProvider</provider> 
     <jta-data-source>jdbc/__JavaAcademy</jta-data-source> 
     <exclude-unlisted-classes>false</exclude-unlisted-classes> 
     <properties> 
      <property name="hibernate.dialect" value="org.hibernate.dialect.MySQLDialect"/> 
      <property name="hibernate.hbm2ddl.auto" value="update"/> 
     </properties> 
    </persistence-unit> 
</persistence>

的pom.xml包含：

 <dependency> 
      <groupId>mysql</groupId> 
      <artifactId>mysql-connector-java</artifactId> 
      <version>5.1.6</version> 
     </dependency> 
     <dependency> 
      <groupId>org.hibernate</groupId> 
      <artifactId>hibernate-core</artifactId> 
      <version>4.3.1.Final</version> 
     </dependency> 
     <dependency> 
      <groupId>org.hibernate</groupId> 
      <artifactId>hibernate-entitymanager</artifactId> 
      <version>4.3.1.Final</version> 
     </dependency> 
     <dependency> 
      <groupId>org.hibernate.javax.persistence</groupId> 
      <artifactId>hibernate-jpa-2.0-api</artifactId> 
      <version>1.0.1.Final</version> 
     </dependency>

感謝您的幫助！

來源

2014-04-26 Bogdan Kobylinsky