JPA错误-名为的EntityManager没有持久性提供程序

Question

我根本无法解决这个问题，而且有大量的堆栈溢出帖子都带有相同的错误消息。我都试过了，但还是没能成功。也许我在寻找一些小东西。我真的需要帮助，提前谢谢你。

错误消息

Initial EntityManagerFactory creation failed.javax.persistence.PersistenceException: No Persistence provider for EntityManager named org.hibernate.ejb.HibernatePersistence
Exception in thread "main" java.lang.ExceptionInInitializerError
    at util.DatabaseUtil.buildSessionFactory(DatabaseUtil.java:18)
    at util.DatabaseUtil.<clinit>(DatabaseUtil.java:8)
    at Test.main(Test.java:68)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144)
Caused by: javax.persistence.PersistenceException: No Persistence provider for EntityManager named org.hibernate.ejb.HibernatePersistence
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:61)
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:39)
    at util.DatabaseUtil.buildSessionFactory(DatabaseUtil.java:13)
    ... 7 more

这是persistence.xml文件

<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_2_0.xsd"
         version="2.0">

  <persistence-unit name="com.learning.jpa">
    <provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>

    <class>com.learning.jpa.entities.User</class>
    <class>com.learning.jpa.entities.Expense</class>
    <class>com.learning.jpa.entities.Category</class>

    <properties>
        <property name="hibernate.connection.pool_size" value="1"/>
        <property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver"/>
        <property name="hibernate.connection.url" value="jdbc:mysql://localhost:3306/budget_calculator"/>
        <property name="hibernate.onnection.username" value="root"/>
        <property name="hibernate.connection.password" value="password"/>
        <property name="hibernate.dialect" value="org.hibernate.dialect.MySQLDialect"/>
        <property name="hibernate.show_sql" value="true"/>
        <property name="hibernate.hbm2ddl.auto" value="update"/>    
    </properties>        
  </persistence-unit>

</persistence>

EntityManagerFactory

public class DatabaseUtil {

    private static EntityManagerFactory sessionFactory = buildSessionFactory();

    private static EntityManagerFactory buildSessionFactory() {
        try {
            if (sessionFactory == null) {
                sessionFactory = Persistence.createEntityManagerFactory("org.hibernate.ejb.HibernatePersistence");
            }
            return sessionFactory;
        } catch (Throwable ex) {
            System.err.println("Initial EntityManagerFactory creation failed." + ex);
            throw new ExceptionInInitializerError(ex);
        }
    }

    public static EntityManagerFactory getSessionFactory() {
        return sessionFactory;
    }

    public static void shutdown() {
        getSessionFactory().close();
    }
}

Answer 1

您对持久性单元使用了错误的标识符。它的名称在这里指定:

...
  <persistence-unit name="com.learning.jpa">
  ...
  </persistence-unit>
</persistence>

StackTrace告诉您：

EntityManager没有名为org.hibernate.ejb.HibernatePersistence的持久性提供程序

因此，您需要在相关代码片段中通过其正确的给定名称 com.learning.jpa 引用 PU，如下所示：

if (sessionFactory == null) {
    sessionFactory = Persistence.createEntityManagerFactory("com.learning.jpa"); 
}

更改为正确的PU名称后，应能正常工作。希望有帮助。