PersistenceContext EntityManager (JPA)

【问题标题】：PersistenceContext EntityManager (JPA)PersistenceContext EntityManager (JPA)
【发布时间】：2018-01-20 12:26:09
【问题描述】：

我正在使用 jpa 创建一个 Java EE 应用程序。 @PersistenceContext(unitName = "airline") 中的问题，当我评论这一行时，它给了我错误 null_pointer_exception 并且当代码在服务器上运行时，它得到以下错误。

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Severe:   Exception while invoking class org.glassfish.persistence.jpa.JPADeployer prepare method
Severe:   java.lang.RuntimeException: Could not resolve a persistence unit corresponding to the persistence-context-ref-name [com.airline.service.PassengerService/entityManager] in the scope of the module called [FlightPassengersJPA]. Please verify your application.
    at com.sun.enterprise.deployment.BundleDescriptor.findReferencedPUViaEMRef(BundleDescriptor.java:731)
    at com.sun.enterprise.deployment.BundleDescriptor.findReferencedPUsViaPCRefs(BundleDescriptor.java:719)
    at org.glassfish.web.deployment.descriptor.WebBundleDescriptorImpl.findReferencedPUs(WebBundleDescriptorImpl.java:1037)
    at org.glassfish.persistence.jpa.JPADeployer.createEMFs(JPADeployer.java:186)
    at org.glassfish.persistence.jpa.JPADeployer.prepare(JPADeployer.java:168)
    at com.sun.enterprise.v3.server.ApplicationLifecycle.prepareModule(ApplicationLifecycle.java:925)
    at com.sun.enterprise.v3.server.ApplicationLifecycle.deploy(ApplicationLifecycle.java:434)
    at com.sun.enterprise.v3.server.ApplicationLifecycle.deploy(ApplicationLifecycle.java:219)
    at org.glassfish.deployment.admin.DeployCommand.execute(DeployCommand.java:491)
    at com.sun.enterprise.v3.admin.CommandRunnerImpl$2$1.run(CommandRunnerImpl.java:539)
    at com.sun.enterprise.v3.admin.CommandRunnerImpl$2$1.run(CommandRunnerImpl.java:535)
    at java.security.AccessController.doPrivileged(Native Method)
    at javax.security.auth.Subject.doAs(Subject.java:360)
    at com.sun.enterprise.v3.admin.CommandRunnerImpl$2.execute(CommandRunnerImpl.java:534)
    at com.sun.enterprise.v3.admin.CommandRunnerImpl$3.run(CommandRunnerImpl.java:565)
    at com.sun.enterprise.v3.admin.CommandRunnerImpl$3.run(CommandRunnerImpl.java:557)
    at java.security.AccessController.doPrivileged(Native Method)
    at javax.security.auth.Subject.doAs(Subject.java:360)
    at com.sun.enterprise.v3.admin.CommandRunnerImpl.doCommand(CommandRunnerImpl.java:556)
    at com.sun.enterprise.v3.admin.CommandRunnerImpl.doCommand(CommandRunnerImpl.java:1464)
    at com.sun.enterprise.v3.admin.CommandRunnerImpl.access$1300(CommandRunnerImpl.java:109)
    at com.sun.enterprise.v3.admin.CommandRunnerImpl$ExecutionContext.execute(CommandRunnerImpl.java:1846)
    at com.sun.enterprise.v3.admin.CommandRunnerImpl$ExecutionContext.execute(CommandRunnerImpl.java:1722)
    at com.sun.enterprise.v3.admin.AdminAdapter.doCommand(AdminAdapter.java:534)
    at com.sun.enterprise.v3.admin.AdminAdapter.onMissingResource(AdminAdapter.java:224)
    at org.glassfish.grizzly.http.server.StaticHttpHandlerBase.service(StaticHttpHandlerBase.java:189)
    at com.sun.enterprise.v3.services.impl.ContainerMapper$HttpHandlerCallable.call(ContainerMapper.java:459)
    at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:167)
    at org.glassfish.grizzly.http.server.HttpHandler.runService(HttpHandler.java:206)
    at org.glassfish.grizzly.http.server.HttpHandler.doHandle(HttpHandler.java:180)
    at org.glassfish.grizzly.http.server.HttpServerFilter.handleRead(HttpServerFilter.java:235)
    at org.glassfish.grizzly.filterchain.ExecutorResolver$9.execute(ExecutorResolver.java:119)
    at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeFilter(DefaultFilterChain.java:283)
    at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeChainPart(DefaultFilterChain.java:200)
    at org.glassfish.grizzly.filterchain.DefaultFilterChain.execute(DefaultFilterChain.java:132)
    at org.glassfish.grizzly.filterchain.DefaultFilterChain.process(DefaultFilterChain.java:111)
    at org.glassfish.grizzly.ProcessorExecutor.execute(ProcessorExecutor.java:77)
    at org.glassfish.grizzly.nio.transport.TCPNIOTransport.fireIOEvent(TCPNIOTransport.java:536)
    at org.glassfish.grizzly.strategies.AbstractIOStrategy.fireIOEvent(AbstractIOStrategy.java:112)
    at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.run0(WorkerThreadIOStrategy.java:117)
    at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.access$100(WorkerThreadIOStrategy.java:56)
    at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy$WorkerThreadRunnable.run(WorkerThreadIOStrategy.java:137)
    at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:591)
    at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.run(AbstractThreadPool.java:571)
    at java.lang.Thread.run(Thread.java:748)
Severe:   Exception while preparing the app
Severe:   Exception during lifecycle processing
java.lang.RuntimeException: Could not resolve a persistence unit corresponding to the persistence-context-ref-name [com.airline.service.PassengerService/entityManager] in the scope of the module called [FlightPassengersJPA]. Please verify your application.
    at com.sun.enterprise.deployment.BundleDescriptor.findReferencedPUViaEMRef(BundleDescriptor.java:731)
    at com.sun.enterprise.deployment.BundleDescriptor.findReferencedPUsViaPCRefs(BundleDescriptor.java:719)
    at org.glassfish.web.deployment.descriptor.WebBundleDescriptorImpl.findReferencedPUs(WebBundleDescriptorImpl.java:1037)
    at org.glassfish.persistence.jpa.JPADeployer.createEMFs(JPADeployer.java:186)
    at org.glassfish.persistence.jpa.JPADeployer.prepare(JPADeployer.java:168)
    at com.sun.enterprise.v3.server.ApplicationLifecycle.prepareModule(ApplicationLifecycle.java:925)
    at com.sun.enterprise.v3.server.ApplicationLifecycle.deploy(ApplicationLifecycle.java:434)
    at com.sun.enterprise.v3.server.ApplicationLifecycle.deploy(ApplicationLifecycle.java:219)
    at org.glassfish.deployment.admin.DeployCommand.execute(DeployCommand.java:491)
    at com.sun.enterprise.v3.admin.CommandRunnerImpl$2$1.run(CommandRunnerImpl.java:539)
    at com.sun.enterprise.v3.admin.CommandRunnerImpl$2$1.run(CommandRunnerImpl.java:535)
    at java.security.AccessController.doPrivileged(Native Method)
    at javax.security.auth.Subject.doAs(Subject.java:360)
    at com.sun.enterprise.v3.admin.CommandRunnerImpl$2.execute(CommandRunnerImpl.java:534)
    at com.sun.enterprise.v3.admin.CommandRunnerImpl$3.run(CommandRunnerImpl.java:565)
    at com.sun.enterprise.v3.admin.CommandRunnerImpl$3.run(CommandRunnerImpl.java:557)
    at java.security.AccessController.doPrivileged(Native Method)
    at javax.security.auth.Subject.doAs(Subject.java:360)
    at com.sun.enterprise.v3.admin.CommandRunnerImpl.doCommand(CommandRunnerImpl.java:556)
    at com.sun.enterprise.v3.admin.CommandRunnerImpl.doCommand(CommandRunnerImpl.java:1464)
    at com.sun.enterprise.v3.admin.CommandRunnerImpl.access$1300(CommandRunnerImpl.java:109)
    at com.sun.enterprise.v3.admin.CommandRunnerImpl$ExecutionContext.execute(CommandRunnerImpl.java:1846)
    at com.sun.enterprise.v3.admin.CommandRunnerImpl$ExecutionContext.execute(CommandRunnerImpl.java:1722)
    at com.sun.enterprise.v3.admin.AdminAdapter.doCommand(AdminAdapter.java:534)
    at com.sun.enterprise.v3.admin.AdminAdapter.onMissingResource(AdminAdapter.java:224)
    at org.glassfish.grizzly.http.server.StaticHttpHandlerBase.service(StaticHttpHandlerBase.java:189)
    at com.sun.enterprise.v3.services.impl.ContainerMapper$HttpHandlerCallable.call(ContainerMapper.java:459)
    at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:167)
    at org.glassfish.grizzly.http.server.HttpHandler.runService(HttpHandler.java:206)
    at org.glassfish.grizzly.http.server.HttpHandler.doHandle(HttpHandler.java:180)
    at org.glassfish.grizzly.http.server.HttpServerFilter.handleRead(HttpServerFilter.java:235)
    at org.glassfish.grizzly.filterchain.ExecutorResolver$9.execute(ExecutorResolver.java:119)
    at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeFilter(DefaultFilterChain.java:283)
    at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeChainPart(DefaultFilterChain.java:200)
    at org.glassfish.grizzly.filterchain.DefaultFilterChain.execute(DefaultFilterChain.java:132)
    at org.glassfish.grizzly.filterchain.DefaultFilterChain.process(DefaultFilterChain.java:111)
    at org.glassfish.grizzly.ProcessorExecutor.execute(ProcessorExecutor.java:77)
    at org.glassfish.grizzly.nio.transport.TCPNIOTransport.fireIOEvent(TCPNIOTransport.java:536)
    at org.glassfish.grizzly.strategies.AbstractIOStrategy.fireIOEvent(AbstractIOStrategy.java:112)
    at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.run0(WorkerThreadIOStrategy.java:117)
    at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.access$100(WorkerThreadIOStrategy.java:56)
    at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy$WorkerThreadRunnable.run(WorkerThreadIOStrategy.java:137)
    at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:591)
    at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.run(AbstractThreadPool.java:571)
    at java.lang.Thread.run(Thread.java:748)

Severe:   Exception while preparing the app : Could not resolve a persistence unit corresponding to the persistence-context-ref-name [com.airline.service.PassengerService/entityManager] in the scope of the module called [FlightPassengersJPA]. Please verify your application.

和我的代码： AddPassenger.java

package com.airline.controllers;

import com.airline.models.FlightClass;
import com.airline.models.Gender;
import com.airline.models.Passenger;
import com.airline.service.PassengerService;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Calendar;
import java.util.Date;
import javax.ejb.EJB;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;


@WebServlet(name = "AddPassenger", urlPatterns = {"/AddPassenger"})
public class AddPassenger extends HttpServlet {

    @EJB
    private PassengerService passengerService;




    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        processRequest(request, response);

        Passenger passenger = new Passenger();

        passenger.setFirstName("Loai");
        passenger.setLastName("Amr");

        Calendar cal = Calendar.getInstance();
        cal.set(Calendar.YEAR, 1996);
        cal.set(Calendar.MONTH, 9);
        cal.set(Calendar.DAY_OF_MONTH, 30);
        Date dob = cal.getTime();

        passenger.setDob(dob);
        passenger.setGender(Gender.Male);
        passenger.setFlightClass(FlightClass.Couch);     

        passengerService.addPassenger(passenger);

        System.out.println("First name : " + passenger.getFirstName());

    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        processRequest(request, response);
    }

    @Override
    public String getServletInfo() {
        return "Short description";
    }// </editor-fold>

}

和类PassengerService：

package com.airline.service;

import com.airline.models.Passenger;
import javax.ejb.EJB;
import javax.ejb.LocalBean;
import javax.ejb.Stateless;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import javax.persistence.PersistenceContextType;

@Stateless
@LocalBean
public class PassengerService {

    public PassengerService() {
    }

    @PersistenceContext(unitName = "airline")
    private EntityManager entityManager;

    public void addPassenger(Passenger passenger) {
        entityManager.persist(passenger);
        System.out.println("Done");
    }

}

和persistence.xml

<?xml version="1.0" encoding="UTF-8"?>
<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="FlightPassengersJPAPU" transaction-type="JTA">
    <provider>org.hibernate.ejb.HibernatePersistence</provider>
    <jta-data-source>jdbc/airline</jta-data-source>
    <exclude-unlisted-classes>false</exclude-unlisted-classes>
    <properties>
      <property name="javax.persistence.schema-generation.database.action" value="create"/>
    </properties>
  </persistence-unit>
</persistence>

【问题讨论】：

    标签： database jpa jakarta-ee glassfish ejb


    【解决方案1】：

    您需要在名为persistence.xml 的文件中定义您的持久性单元。这应该作为 META-INF 中的资源。

    您可以在以下位置看到一个示例： persistence.xml...你看到的数据源是在wildfly的配置中定义的，你可以在standalone.xml看到它

    以类似的方式，我认为您确实在 glassfish 中定义了数据源。

    【讨论】：

    • 我做了但没用
    • 那么 jdbc/airline 是在 glassfish 中定义的，如何？您可以尝试： Persistence.createEntityManagerFactory("FlightPassengersJPAPU").createEntityManager() 在您的代码中吗？那么返回什么？
    • FlightPassengersJPAPU != 您需要使用持久化单元的名称属性作为@PersistenceUnit 的单元名称的航空公司：@PersistenceUnit(unitName="FlightPassengersJPAPU")
    • @PersistenceUnit(unitName="FlightPassengersJPAPU") public void addPassenger(Passenger Passenger) { EntityManager createEntityManager; createEntityManager = Persistence.createEntityManagerFactory("FlightPassengersJPAP‌U").createEntityMana‌ger(); createEntityManager.persist(乘客); System.out.println("完成"); }
    • 我这样做并给了我错误：javax.persistence.PersistenceException: No Persistence provider for EntityManager named FlightPassengersJPAP‌U
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