javax.persistence.PersistenceException：没有名为customerManager的EntityManager的持久性提供者 [英] javax.persistence.PersistenceException: No Persistence provider for EntityManager named customerManager

问题描述

我是JPA&休眠。在阅读了一些在线资料后，我现在了解了Hibernate是什么以及它如何与JPA一起使用。

现在，我试图运行这个 JPA& Hibernate教程。我已经完成了本教程中提到的所有内容。

我没有Oracle DB，只有MySQL。所以我使用我对JPA&我的理解对 persistence.xml 做了一些修改。 Hibernate（我不知道它是否正确......对我来说就是这样。）

这是我的 persistence.xml

 < persistence xmlns =http://java.sun.com/xml/ns/持久性xmlns：xsi =http://www.w3.org/2001/XMLSchema-instancexsi：schemalocation =http://java.sun.com/xml/ns/persistence http：//java.sun .com / xml / ns / persistence / persistence_1_0.xsdversion =1.0> 
< persistence-unit name =customerManagertransaction-type =RESOURCE_LOCAL> 
< provider> org.hibernate.ejb.HibernatePersistence< / provider> 
< class>客户< / class> 
<属性> 
< property name =hibernate.dialectvalue =org.hibernate.dialect.MySQLInnoDBDialect/> 
< property name =hibernate.connection.driver_classvalue =com.mysql.jdbc.Driver/> 
< property name =hibernate.show_sqlvalue =true/> 
< property name =hibernate.connection.usernamevalue =root/> 
< property name =hibernate.connection.passwordvalue =1234/> 
 < property name =hibernate.max_fetch_depthvalue =3/> 
< / properties> 
< / persistence-unit> 
< /余辉> 
  

但我似乎没有得到他们描述的输出。它给了我：

 创建之前的客户id：null 
 log4j：WARN无法为记录器找到appender（组织.hibernate.cfg.annotations.Version）。 
 log4j：WARN请正确初始化log4j系统。 
线程main中的异常javax.persistence.PersistenceException：否EntityManager的持久性提供程序，名称为customerManager $ b $，位于javax.persistence.Persistence.createEntityManagerFactory（Persistence.java:55）
，位于javax.persistence CustomerDAO.create（CustomerDAO.java:8）
在CustomerDAO.main（CustomerDAO.java:22）
  at CustomerDAO.create c> 

欢迎您提出任何建议。



更新：



我已完成要求完成的更改。但是，仍然得到asme错误行!!!



在本教程中，他们没有提及任何关于 orm.xml 的内容。可能它是一个问题！

解决方案

您的 persistence.xml 无效，并且 EntityManagerFactory 无法创建。它应该是：

 < persistence xmlns =http://java.sun.com/xml/ns/persistence xmlns：xsi =http://www.w3.org/2001/XMLSchema-instancexsi：schemalocation =http://java.sun.com/xml/ns/persistence http://java.sun.com /xml/ns/persistence/persistence_1_0.xsdversion =1.0> 
< persistence-unit name =customerManagertransaction-type =RESOURCE_LOCAL> 
< provider> org.hibernate.ejb.HibernatePersistence< / provider> 
< class>客户< / class> 
<属性> 
< property name =hibernate.dialectvalue =org.hibernate.dialect.MySQLInnoDBDialect/> 
< property name =hibernate.connection.driver_classvalue =com.mysql.jdbc.Driver/> 
< property name =hibernate.show_sqlvalue =true/> 
< property name =hibernate.connection.usernamevalue =root/> 
< property name =hibernate.connection.passwordvalue =1234/> 
 < property name =hibernate.max_fetch_depthvalue =3/> 
< / properties> 
< / persistence-unit> 
< /余辉> 
  

（注意< property> 元素是关闭的，它们不应该嵌套）

更新：我阅读了教程，您还必须更改 Id 使用MySQL时的生成策略（因为MySQL不支持序列）。我建议使用 AUTO 策略（默认为使用MySQL的IDENTITY）。为此，删除 SequenceGenerator 注释并更改代码，如下所示：

  @Entity 
 @Table（name =TAB_CUSTOMER）
 public class Customer实现Serializable {
 private static final long serialVersionUID = 1L; 
 
 @Id 
 @GeneratedValue（strategy = GenerationType.AUTO）
 @Column（name =CUSTOMER_ID，precision = 0）
 private long customerId = null; 
 
 ... 
} 
  

这应该有所帮助。 / p>

PS：您还应该按照建议提供 log4j.properties 。

I am new to JPA & Hibernate. After reading some online materials I now understand what Hibernate is and how it can be used with JPA.

Now, I am trying to run this JPA & Hibernate tutorial. I've done everything they mention in this tutorial.

I don't have Oracle DB, only MySQL. So I made some changes to persistence.xml using my understanding of JPA & Hibernate (I don't know if it's correct or not... Seems to me it is.)

Here is my persistence.xml

<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">
  <persistence-unit name="customerManager" transaction-type="RESOURCE_LOCAL">
    <provider>org.hibernate.ejb.HibernatePersistence</provider>
    <class>Customer</class>
    <properties>
      <property name="hibernate.dialect" value="org.hibernate.dialect.MySQLInnoDBDialect"/>
      <property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver"/>
      <property name="hibernate.show_sql" value="true"/>
      <property name="hibernate.connection.username" value="root"/>
      <property name="hibernate.connection.password" value="1234"/>
      <property name="hibernate.connection.url" value="jdbc:mysql://localhost:3306/general"/>
      <property name="hibernate.max_fetch_depth" value="3"/>
    </properties>
  </persistence-unit>
</persistence>

But I don't seem to get the output they describe. It's giving me:

Customer id before creation:null
log4j:WARN No appenders could be found for logger (org.hibernate.cfg.annotations.Version).
log4j:WARN Please initialize the log4j system properly.
Exception in thread "main" javax.persistence.PersistenceException: No Persistence     provider for EntityManager named customerManager
 at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:55)
 at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:33)
 at CustomerDAO.create(CustomerDAO.java:8)
 at CustomerDAO.main(CustomerDAO.java:22)

Any suggestions will be appreciated.

Update:

I have made the changes that are asked to done. But, still getting the asme error lines!!!

They didnt mentioned anything about orm.xml in that tutorial. may it be a problem causer!!!

解决方案

Your persistence.xml is not valid and the EntityManagerFactory can't get created. It should be:

<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">
  <persistence-unit name="customerManager" transaction-type="RESOURCE_LOCAL">
    <provider>org.hibernate.ejb.HibernatePersistence</provider>
    <class>Customer</class>
    <properties>
      <property name="hibernate.dialect" value="org.hibernate.dialect.MySQLInnoDBDialect"/>
      <property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver"/>
      <property name="hibernate.show_sql" value="true"/>
      <property name="hibernate.connection.username" value="root"/>
      <property name="hibernate.connection.password" value="1234"/>
      <property name="hibernate.connection.url" value="jdbc:mysql://localhost:3306/general"/>
      <property name="hibernate.max_fetch_depth" value="3"/>
    </properties>
  </persistence-unit>
</persistence>

(Note how the <property> elements are closed, they shouldn't be nested)

Update: I went through the tutorial and you will also have to change the Id generation strategy when using MySQL (as MySQL doesn't support sequences). I suggest using the AUTO strategy (defaults to IDENTITY with MySQL). To do so, remove the SequenceGenerator annotation and change the code like this:

@Entity
@Table(name="TAB_CUSTOMER")
public class Customer implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    @Column(name="CUSTOMER_ID", precision=0)
    private Long customerId = null;

   ...
}

This should help.

PS: you should also provide a log4j.properties as suggested.

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