沒有持久性提供 「EntityManager的」 命名 「firstOne的」 Java

Question

我使用persistense API連接到數據庫

這是pom.xml的dependendcies

<groupId>org.hibernate</groupId> 
    <artifactId>hibernate-core</artifactId> 
    <version>4.2.8.Final</version> 
    </dependency> 
    <dependency> 
    <groupId>postgresql</groupId> 
    <artifactId>postgresql</artifactId> 
    <version>9.1-901.jdbc4</version> 
    </dependency> 
    <dependency> 
    <groupId>javax.persistence</groupId> 
    <artifactId>persistence-api</artifactId> 
    <version>1.0.2</version> 

persistense.xml：

<?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" 
    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="firstOne"> 
     <provider>org.hibernate.ejb.HibernatePersistence</provider> 
     <properties> 
      <property name="hibernate.ejb.cfgfile" value="/META-INF/hibernate.cfg.xml" /> 
     </properties> 
    </persistence-unit> 
</persistence> 

的hibernate.cfg.xml：

<?xml version="1.0" encoding="UTF-8"?> 
<!DOCTYPE hibernate-configuration PUBLIC 
     "-//Hibernate/Hibernate Configuration DTD 3.0//EN" 
     "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"> 
    <hibernate-configuration> 
<session-factory> 
    <property name="connection.driver_class">org.postgresql.Driver</property> 
    <property name="dialect">org.hibernate.dialect.PostgreSQLDialect</property> 
    <property name="hibernate.connection.username">postgres</property> 
    <property name="hibernate.connection.password">tauren993</property> 
    <property name="hibernate.connection.url">jdbc:postgresql://localhost:5432/hibernate</property> 
    <property name="hibernate.hbm2ddl.auto">create</property> 
    <property name="hibernate.generate_statistics">false</property> 
    <property name="show_sql">true</property> 
    <property name="format_sql">true</property> 
    <property name="hibernate.cache.use_structured_entries">false</property> 
    <property name="hibernate.cache.use_second_level_cache">false</property> 

    <mapping class="Employee" /> 
</session-factory> 
</hibernate-configuration> 

的hibernate.cfg.xml和persistense.xml存儲項目/ META-INF文件夾，然後我得到的

EntityManagerFactory emf = Persistence.createEntityManagerFactory("firstOne"); 

堆棧跟蹤錯誤：

javax.persistence.PersistenceException: No Persistence provider for EntityManager named firstOne 
at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:69) 
at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:47) 
at Main.main(Main.java:14) 

Answer 1

在您的持久性單元「firstOne 「你應該包括提供者。如下所示：

<persistence-unit name="firstOne"> 
    <provider>org.hibernate.ejb.HibernatePersistence</provider> 

Answer 2

您可能會錯過實體聲明。如果您處於JAVA EE環境中，請確保您的項目中有一些註釋爲實體的類。如果你能

<persistence-unit name="OrderManagement"> 
    [...] 
    <jar-file>MyOrderApp.jar</jar-file> 
    or/and 
    <class>com.widgets.Order</class> 
    <class>com.widgets.Customer</class> 
</persistence-unit> 

此外，

你應該使用JPA 2：否則，在Java SE環境下，你必須定義提供商爲thiyaga說（見doc）和下面指定的實體

您不需要hibernate.cfg.xml文件，只需將您的屬性直接放入persitence.xml文件的<properties>元素中，確保休眠屬性的前綴爲hibernate。