为什么EntityManager为空? [英] why EntityManager is null?
问题描述
在我的网络应用程序中,我在Apache Tomcat(TomEE)/7.0.37服务器上使用OpenJPA。我使用Netbeans自动生成类(来自数据库的实体类......和来自实体类的会话Bean ......)。在SessionBean(例如UserFacade)我想获得EntityManager:
In my web applicaton I use OpenJPA on Apache Tomcat (TomEE)/7.0.37 server. I use Netbeans to auto generate class ("Entity Class from database..." and "Session Beans From Entity Class..."). At SessionBean (for example UserFacade) i want to get EntityManager:
@Stateless
public class UserFacade extends AbstractFacade<User> {
@PersistenceContext(unitName = "CollDocPU")
private EntityManager em;
@Override
protected EntityManager getEntityManager() {
return em;
}
}
但是当我通过上面的方式得到它时我得到null 。
当我通过:
but when i get it by above way I get null. When I make it by:
@Override
protected EntityManager getEntityManager() {
EntityManagerFactory emf = Persistence.createEntityManagerFactory("CollDocPU");
EntityManager ecm = emf.createEntityManager();
return ecm;
}
ecm不为空且没问题
ecm is not null and it ok
我的persistence.xml:
my 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="CollDocPU" transaction-type="RESOURCE_LOCAL">
<provider>org.apache.openjpa.persistence.PersistenceProviderImpl</provider>
<class>model.entity.StudentAddSolution</class>
<class>model.entity.Lecturer</class>
<class>model.entity.Solution</class>
<class>model.entity.Student</class>
<class>model.entity.Course</class>
<class>model.entity.File</class>
<class>model.entity.CourseHasLecturer</class>
<class>model.entity.Mail</class>
<class>model.entity.StudentAtCourse</class>
<class>model.entity.Roles</class>
<class>model.entity.Task</class>
<class>model.entity.User</class>
<exclude-unlisted-classes>false</exclude-unlisted-classes>
<properties>
<property name="javax.persistence.jdbc.url" value="jdbc:mysql://localhost:11080/myBase?zeroDateTimeBehavior=convertToNull"/>
<property name="javax.persistence.jdbc.password" value="pass,"/>
<property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver"/>
<property name="javax.persistence.jdbc.user" value="myBase"/>
<property name="openjpa.jdbc.SynchronizeMappings" value="buildSchema(ForeignKeys=true)"/>
</properties>
</persistence-unit>
</persistence>
推荐答案
从
@PersistenceContext(unitName = "CollDocPU")
private EntityManager em;
我必须更改我的persistance.xml,将事务类型更改为JTA并添加:
i have to change my persistance.xml, change transaction-type to "JTA" and add:
<jta-data-source>java:openejb/Resource/myDatabase</jta-data-source>
<non-jta-data-source>java:openejb/Resource/myDatabaseUnmanaged</non-jta-data-source>
之后,我必须在我的服务器配置中声明资源:at [tomee installation folder] / conf /tomee.xml文件:
after that, i have to declare resources in my server configuration: at [tomee installation folder]/conf/tomee.xml file:
<?xml version="1.0" encoding="UTF-8"?>
<tomee>
<Resource id="myDatabase" type="DataSource">
JdbcDriver com.mysql.jdbc.Driver
JdbcUrl jdbc:mysql://localhost:11080/jkitaj?zeroDateTimeBehavior=convertToNull
UserName jkitaj
Password pass,
</Resource>
<Resource id="myDatabaseUnmanaged" type="DataSource">
JdbcDriver com.mysql.jdbc.Driver
JdbcUrl jdbc:mysql://localhost:11080/jkitaj?zeroDateTimeBehavior=convertToNull
UserName jkitaj
Password pass,
JtaManaged false
</Resource>
</tomee>
看那里:
http://mobiarch.wordpress.com/2012/12/07/configuring-a-mysql-data-source-in-tomee/
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