Java entitymanager错误JPA/hibernate没有持久性提供程序

我想使用JPA/hibernate添加数据库和持久化数据。我将persistence.xml放在了正确的位置，但没有针对entitymanager错误的持久性提供程序。数据库在mysql中。任何建议都将不胜感激。这是我的密码：

文件夹结构：

servlet：

JPA持久性的服务类：

persistence.xml：

错误：

更新

我添加lib文件夹是为了显示我为项目添加的jar文件，因为我没有使用maven

更新2

---

我最终使用了maven，它现在可以工作了。有关pom.xml，请参见下面@Surace的答案。

将persistence.xml更改为

<persistence version="2.1"
xmlns="http://xmlns.jcp.org/xml/ns/persistence" 
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd">
<persistence-unit name="ReservationsPU">
    <provider>org.hibernate.ejb.HibernatePersistence</provider>
    <properties>
        <property name="hibernate.connection.url" value="jdbc:mysql://localhost:3306/world" />
        <property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver" />
        <property name="hibernate.connection.username" value="root" />
        <property name="hibernate.connection.password" value="password" />
        <property name="hibernate.dialect" value="org.hibernate.dialect.MySQL5Dialect" />
        <property name="hibernate.hbm2ddl.auto" value="create" />
        <property name="hibernate.show_sql" value="true" />
        <property name="use_sql_comments" value="true" />
        <property name="hibernate.format_sql" value="true" />
    </properties>
</persistence-unit>

如果使用Maven，请在pom.xml中添加以下依赖项

<dependencies>

    <dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-entitymanager</artifactId>
        <version>5.1.0.Final</version>
    </dependency>
    <dependency>
        <groupId>org.hibernate.javax.persistence</groupId>
        <artifactId>hibernate-jpa-2.1-api</artifactId>
        <version>1.0.0.Final</version>
    </dependency>
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>5.1.37</version>
    </dependency>

</dependencies>

---

我认为问题在于日食。Eclipse可能只允许运行显式设置为JPA项目的JPA

---

通过在资源管理器中打开上下文菜单，您可以将项目转换为JPA项目。

顺便说一句，您的实体应该有一个id。@MouseEvent，我有一个id。我更新了question@ScaryWombat，根据JPA文档，我只需要在配置持久性单元的地方添加persistence.xml。我没有；我看不到关于web.xml的任何信息。你是说我也必须在web.xml中添加配置吗？@JoeZ我自己也不确定，因此根据你更新的问题，Eclipse中的构建错误是什么？我想使用JPA 2.1版本，这就是我使用此提供程序的原因。但我也试过你的，同样的错误。出于某种原因，它没有得到persistence.xml配置。根据Jpa文档，我遵循了所有的步骤。您还应该在pom.xml中添加依赖项。可能我错过了，但我看不到OP提到他正在使用Maven。我认为最好提到hibernate-entitymanager.jar应该在classpath中，如果他使用Maven，则使用pom.xml作为示例。我认为很可能OP没有使用Maven，基于他显示的目录结构yes@AdrianShum你是对的，他没有使用Maven。乔兹，你试过上面的答案吗？您的库文件夹中有jar吗？

public class ReservationSevice 
{
    static EntityManagerFactory emf = Persistence.createEntityManagerFactory("ReservationsPU");
    private static EntityManager em = emf.createEntityManager(); 

    public void createReservation (ReservationEntity reservation)
    {
        em.getTransaction().begin();
        em.persist(reservation);
        em.getTransaction().commit();
    }
}

<persistence version="2.1"
    xmlns="http://xmlns.jcp.org/xml/ns/persistence" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd">
    <persistence-unit name="ReservationsPU">
        <provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
        <properties>
            <property name="hibernate.connection.url" value="jdbc:mysql://localhost:3306/world" />
            <property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver" />
            <property name="hibernate.connection.username" value="root" />
            <property name="hibernate.connection.password" value="password" />
            <property name="hibernate.archive.autodetection" value="class" />
            <property name="hibernate.show_sql" value="true" />
            <property name="hibernate.format_sql" value="true" />
            <property name="hibernate.dialect" value="org.hibernate.dialect.MySQL5InnoDBDialect" />
            <property name="hbm2ddl.auto" value="update" />
        </properties>
    </persistence-unit>
</persistence>

javax.persistence.PersistenceException: No Persistence provider for EntityManager named ReservationsPU
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:61)
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:39)
    at com.welcomelimo.service.ReservationSevice.<init>(ReservationSevice.java:11)
    at com.welcomelimo.controller.Reservations.doPost(Reservations.java:56)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:648)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:292)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:212)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:141)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:528)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1099)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:670)
    at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.doRun(AprEndpoint.java:2508)
    at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2497)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:745)
Exception occured

<persistence version="2.1"
xmlns="http://xmlns.jcp.org/xml/ns/persistence" 
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd">
<persistence-unit name="ReservationsPU">
    <provider>org.hibernate.ejb.HibernatePersistence</provider>
    <properties>
        <property name="hibernate.connection.url" value="jdbc:mysql://localhost:3306/world" />
        <property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver" />
        <property name="hibernate.connection.username" value="root" />
        <property name="hibernate.connection.password" value="password" />
        <property name="hibernate.dialect" value="org.hibernate.dialect.MySQL5Dialect" />
        <property name="hibernate.hbm2ddl.auto" value="create" />
        <property name="hibernate.show_sql" value="true" />
        <property name="use_sql_comments" value="true" />
        <property name="hibernate.format_sql" value="true" />
    </properties>
</persistence-unit>

<dependencies>

    <dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-entitymanager</artifactId>
        <version>5.1.0.Final</version>
    </dependency>
    <dependency>
        <groupId>org.hibernate.javax.persistence</groupId>
        <artifactId>hibernate-jpa-2.1-api</artifactId>
        <version>1.0.0.Final</version>
    </dependency>
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>5.1.37</version>
    </dependency>

</dependencies>