仍然得到 PersistenceException: No Persistence provider for EntityManager答案

【问题标题】：Still getting PersistenceException: No Persistence provider for EntityManager仍然得到 PersistenceException: No Persistence provider for EntityManager
【发布时间】：2014-04-26 22:57:20
【问题描述】：

部署我的应用程序后出现这样的异常：

Caused by: javax.persistence.PersistenceException: No Persistence provider for EntityManager named JavaAcademyUnit
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:85)
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:54)
    at com.bogdankobylinsky.javaacademy.dao.impl.jpa.UserJPADAO.<init>(UserJPADAO.java:13)

，在这一行失败：

 private EntityManager em = Persistence.createEntityManagerFactory("JavaAcademyUnit").createEntityManager();

JPA 配置描述符persistance.xml 文件位于正确的位置：./WEB-INF/classes/META-INF/persistence.xml 并包含：

<persistence xmlns="http://java.sun.com/xml/ns/persistence" version="2.0">
    <persistence-unit name="JavaAcademyUnit" transaction-type="JTA">
        <provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
        <jta-data-source>jdbc/__JavaAcademy</jta-data-source>
        <exclude-unlisted-classes>false</exclude-unlisted-classes>
        <properties>
            <property name="hibernate.dialect" value="org.hibernate.dialect.MySQLDialect"/>
            <property name="hibernate.hbm2ddl.auto" value="update"/>
        </properties>
    </persistence-unit>
</persistence>

pom.xml 包含：

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.6</version>
        </dependency>
        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-core</artifactId>
            <version>4.3.1.Final</version>
        </dependency>
        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-entitymanager</artifactId>
            <version>4.3.1.Final</version>
        </dependency>
        <dependency>
            <groupId>org.hibernate.javax.persistence</groupId>
            <artifactId>hibernate-jpa-2.0-api</artifactId>
            <version>1.0.1.Final</version>
        </dependency>

感谢您的帮助！

【问题讨论】：

标签： java hibernate jpa entitymanager persistence.xml

【解决方案1】：

终于，经过4个小时的谷歌搜索，我找到了原因：

Artifacts 文件夹的根目录中必须有 lib 文件夹以及所需的库：

希望对某人有所帮助。

【讨论】：