1

我有一个带有 Tomcat 7 和 Hibernate 4.3 的简单 servlet 项目,但是当我尝试使用 Hibernate 但不知道发生了什么时出现错误。

基本上,我的 servlet 调用Persistence.createEntityManagerFactory(PERSISTENCE_UNIT)工厂,它调用factory.createEntityManager()实体管理器,它将尝试持久化使用来自 Http 请求的参数创建的对象。当我调用java.lang.ClassNotFoundException: javax.persistence.Persistence第一个方法从Persistence. 这是堆栈:

unit1是我的包裹)

java.lang.ClassNotFoundException: javax.persistence.Persistence
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1714)
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1559)
    at unit1.dao_hibernate.HibernateDaoAluno.inserir(HibernateDaoAluno.java:16)
    at unit1.servlet.CadastroAluno.doPost(CadastroAluno.java:29)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:647)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:953)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1023)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:312)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)

这是 HibernateDaoAluno.java:16 行:

EntityManagerFactory factory = Persistence.createEntityManagerFactory(PERSISTENCE_UNIT);

考虑

private static final String PERSISTENCE_UNIT = "lpoo2_unit1";

这是我的persistence.xml文件,在 META-INF 文件夹中:

<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="lpoo2_unit1">
        <!-- provedor/implementacao do JPA -->
        <provider>org.hibernate.ejb.HibernatePersistence</provider>

        <!-- entidade mapaeada -->
        <class>unit1.model.Aluno</class>
        <class>unit1.model.Disciplina</class>
        <class>unit1.model.Professor</class>
        <class>unit1.model.Turma</class>

        <properties>
            <!-- dados da conexao -->
            <property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver" />
            <property name="javax.persistence.jdbc.url" value="jdbc:mysql://localhost/lpoo2" />
            <property name="javax.persistence.jdbc.user" value="root" />
            <property name="javax.persistence.jdbc.password" value="root" />

            <!-- propriedades do hibernate -->
            <property name="hibernate.dialect" value="org.hibernate.dialect.MySQL5InnoDBDialect" />
            <property name="hibernate.show_sql" value="false" />
            <property name="hibernate.format_sql" value="true" />

            <!-- atualiza o banco, gera as tableas se for preciso -->
            <property name="hibernate.hbm2ddl.auto" value="update" />

        </properties>
    </persistence-unit>

</persistence>

我究竟做错了什么?我需要帮助。谢谢!

4

1 回答 1

3

您的类路径缺少 javax.persistence 库。这是 Java EE SDK 的一部分(您可能会在开发应用程序时使用它,但它不是Java SE SDK 的一部分,您肯定会使用它来运行 Tomcat 应用程序服务器。

解决方案:

  • 将 javax.persistence 库添加到类路径
  • (或者)使用 Java EE 环境来运行你的 tomcat。

请记住,您可以在调用 java 时将库添加到类路径中,将其设置为 tomcat 的参数,将其添加到共享库或将其添加到 Web 应用程序的“lib”目录。

于 2013-09-29T20:23:02.950 回答