Could not open JPA EntityManager for transaction

 A JDBC Driver or DataSource class name must be specified in the ConnectionDriverName property.
ConnectionDriverName属性没有配置，发下配置看看

检查一下 数据源 配置， 看你的异常应该是 使用 JTA 事物 ，容器没有实例化 EntityManager  

<persistence-unit name=”main-persistence” transaction-type=”RESOURCE_LOCAL”>
<class>org.hibernate.ejb.HibernatePersistence</class>
<properties>
<!– 数据库方言 –>
<property name=”hibernate.dialect” value=”org.hibernate.dialect.MySQL5Dialect”/>
<property name=”hibernate.connection.driver_class” value=”com.mysql.jdbc.Driver”/>
<property name=”hibernate.connection.url” value=”jdbc:mysql://localhost:3306/sm?useUnicode=true&amp;characterEncoding=utf-8″ />
<property name=”hibernate.connection.username” value=”root” />
<property name=”hibernate.connection.password” value=”root” />
        <property name=”hibernate.cache.provider_class” value=”org.hibernate.cache.HashtableCacheProvider”/>   
        <property name=”hibernate.show_sql” value=”true” />  
        <property name=”hibernate.jdbc.batch_size” value=”10″/>
<property name=”connection.autoReconnect” value=”true”/> 
        <property name=”connection.autoReconnectForPools” value=”true”/> 
        <property name=”connection.is-connection-validation-required” value=”true”/> 
</properties>
</persistence-unit>

引用 2 楼 lvzg_005 的回复:

A JDBC Driver or DataSource class name must be specified in the ConnectionDriverName property.
ConnectionDriverName属性没有配置，发下配置看看

<persistence-unit name=”main-persistence” transaction-type=”RESOURCE_LOCAL”>
<class>org.hibernate.ejb.HibernatePersistence</class>
<properties>
<!– 数据库方言 –>
<property name=”hibernate.dialect” value=”org.hibernate.dialect.MySQL5Dialect”/>
<property name=”hibernate.connection.driver_class” value=”com.mysql.jdbc.Driver”/>
<property name=”hibernate.connection.url” value=”jdbc:mysql://localhost:3306/sm?useUnicode=true&amp;characterEncoding=utf-8″ />
<property name=”hibernate.connection.username” value=”root” />
<property name=”hibernate.connection.password” value=”root” />
        <property name=”hibernate.cache.provider_class” value=”org.hibernate.cache.HashtableCacheProvider”/>   
        <property name=”hibernate.show_sql” value=”true” />  
        <property name=”hibernate.jdbc.batch_size” value=”10″/>
<property name=”connection.autoReconnect” value=”true”/> 
        <property name=”connection.autoReconnectForPools” value=”true”/> 
        <property name=”connection.is-connection-validation-required” value=”true”/> 
</properties>
</persistence-unit>

<?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”
version=”1.0″>
<persistence-unit name=”coffee” transaction-type=”JTA”>
<provider>org.apache.openjpa.persistence.PersistenceProviderImpl</provider>
<jta-data-source>osgi:service/javax.sql.DataSource/(osgi.jndi.service.name=jdbc/oracleds)</jta-data-source>

<class>com.inetpsa.coffee.example.representations.DepartmentRepresentation</class>
<class>com.inetpsa.coffee.example.representations.EmployeeRepresentation</class>

<exclude-unlisted-classes>true</exclude-unlisted-classes>
<properties>
<property name=”openjpa.LockManager” value=”pessimistic”/>
</properties>
</persistence-unit>
</persistence>

参考下，

 A JDBC Driver or DataSource class name must be specified in the ConnectionDriverName property.
说的清楚啊！你的driver的name找不到匹配的驱动！好像是driverClass不是driver_class!

http://blog.csdn.net/dongja3/article/details/44617137