java - org.hibernate.MappingException : Unknown entity when trying to create a new record

Question

我想使用 Hibernate 和 Spring MVC 在 MySQL 中实现简单的 CRUD 操作。我在 Spring MVC 中制作了一些 Web 应用程序，但 Hibernate 对我来说还很陌生。我尝试在数据库的一个表中创建一条记录，并按照本教程进行操作:https://examples.javacodegeeks.com/enterprise-java/hibernate/hibernate-crud-operations-tutorial/但是当我运行该应用程序时，它给出了 org.hibernate.MappingException

我尝试过从文件 hibernate-cfg.xml 中保留和删除映射类行。我还检查了是否缺少 @Entity 注释。

异常堆栈:

org.hibernate.MappingException: Unknown entity: com.eversoft.traverse.model.User
    at org.hibernate.metamodel.internal.MetamodelImpl.entityPersister(MetamodelImpl.java:704)
    at org.hibernate.internal.SessionImpl.getEntityPersister(SessionImpl.java:1731)
    at org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:118)
    at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:191)
    at org.hibernate.event.internal.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:38)
    at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:176)
    at org.hibernate.event.internal.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:32)
    at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:73)
    at org.hibernate.internal.SessionImpl.fireSave(SessionImpl.java:712)
    at org.hibernate.internal.SessionImpl.save(SessionImpl.java:704)
    at org.hibernate.internal.SessionImpl.save(SessionImpl.java:699)
    at com.eversoft.traverse.daoimpl.UserDaoImpl.createUser(UserDaoImpl.java:43)
    at com.eversoft.traverse.serviceimpl.UserServiceImpl.createUser(UserServiceImpl.java:22)
    at com.eversoft.traverse.controller.UserController.addUserDummy(UserController.java:31)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:567)
    at org.springframework.web.method.support.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:213)
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:126)
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:96)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:617)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:578)
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:80)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:923)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:852)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:882)
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:778)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:634)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:490)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:668)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:408)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:791)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1417)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
    at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.base/java.lang.Thread.run(Thread.java:835)

用户.java

package com.eversoft.traverse.model;

import java.io.Serializable;
import java.util.Date;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name="users")
public class User implements Serializable{
    private static final long serialVersionUID = 1L;

    @Id
    @Column(name="id")
    @GeneratedValue(strategy=GenerationType.AUTO)
    private int id;

    @Column(name="firstName")
    private String firstName;

    @Column(name="middleName")
    private String middleName;

    @Column(name="lastName")
    private String lastName;

    @Column(name="nationality")
    private String nationality;

    @Column(name="dateOfBirth")
    public Date dateOfBirth;

    @Column(name="visaId")
    private int visaId;

    public User() {

    }

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getMiddleName() {
        return middleName;
    }

    public void setMiddleName(String middleName) {
        this.middleName = middleName;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public String getNationality() {
        return nationality;
    }

    public void setNationality(String nationality) {
        this.nationality = nationality;
    }

    public Date getDateOfBirth() {
        return dateOfBirth;
    }

    public void setDateOfBirth(Date dateOfBirth) {
        this.dateOfBirth = dateOfBirth;
    }

    public int getVisaId() {
        return visaId;
    }

    public void setVisaId(int visaId) {
        this.visaId = visaId;
    }


}

UserController.java

package com.eversoft.traverse.controller;

import java.util.Date;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

import com.eversoft.traverse.model.User;
import com.eversoft.traverse.service.UserService;

@Controller
public class UserController {

    @Autowired
    UserService userService;

    @RequestMapping(value="/adddummyvalue", method = RequestMethod.GET)
    public String addUserDummy(Model model) {

        User dummyUser = new User();
        dummyUser.setDateOfBirth(new Date());
        dummyUser.setFirstName("Bikalpa");
        dummyUser.setLastName("Dhakal");
        dummyUser.setMiddleName("Raj");
        dummyUser.setNationality("Nepalese");
        dummyUser.setVisaId(22);

        userService.createUser(dummyUser);

        return "home";
    }
}

UserDaoImpl.java

package com.eversoft.traverse.daoimpl;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;
import org.springframework.stereotype.Repository;

import com.eversoft.traverse.dao.UserDao;
import com.eversoft.traverse.model.User;

@Repository
public class UserDaoImpl implements UserDao {

    static Session sessionObj;
    static SessionFactory sessionFactoryObj;

    //public final static Logger logger = Logger.getLogger(DbOperations.class);

    // This Method Is Used To Create The Hibernate's SessionFactory Object
    private static SessionFactory buildSessionFactory() {
        // Creating Configuration Instance & Passing Hibernate Configuration File
        Configuration configObj = new Configuration();
        configObj.configure("hibernate.cfg.xml");

        // Since Hibernate Version 4.x, ServiceRegistry Is Being Used
        ServiceRegistry serviceRegistryObj = new StandardServiceRegistryBuilder().applySettings(configObj.getProperties()).build(); 

        // Creating Hibernate SessionFactory Instance
        sessionFactoryObj = configObj.buildSessionFactory(serviceRegistryObj);
        return sessionFactoryObj;
    }

    @Override
    public void createUser(User user) {
        try {
            // Getting Session Object From SessionFactory
            sessionObj = buildSessionFactory().openSession();
            // Getting Transaction Object From Session Object
            sessionObj.beginTransaction();

            sessionObj.save(user);

            // Committing The Transactions To The Database
            sessionObj.getTransaction().commit();
        } catch(Exception sqlException) {
            if(null != sessionObj.getTransaction()) {
                sessionObj.getTransaction().rollback();
            }
            sqlException.printStackTrace();
        } finally {
            if(sessionObj != null) {
                sessionObj.close();
            }
        }
    }

}

UserServiceImpl.java

package com.eversoft.traverse.serviceimpl;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import com.eversoft.traverse.dao.UserDao;
import com.eversoft.traverse.model.User;
import com.eversoft.traverse.service.UserService;

@Service
public class UserServiceImpl implements UserService{

    @Autowired
    UserDao userDao;

    public UserServiceImpl() {

    }

    @Override
    public void createUser(User user) {
        userDao.createUser(user);
    }

}

hibernate-cfg.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC
        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
        "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">

<hibernate-configuration>
    <session-factory>
        <!-- SQL Dialect -->
        <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>

        <!-- Database Connection Settings -->
        <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="hibernate.connection.url">jdbc:mysql://localhost:3306/sys</property>
        <property name="hibernate.connection.username">root</property>
        <property name="hibernate.connection.password">helloworld</property>
        <property name="show_sql">true</property>

        <!-- Specifying Session Context -->
        <property name="hibernate.current_session_context_class">org.hibernate.context.internal.ThreadLocalSessionContext</property>

        <!-- <mapping class="com.eversoft.traverse.model.User" /> -->
        <!-- Mapping With Model Class Containing Annotations -->
        <!-- <mapping class="com.jcg.hibernate.crud.operations.Student" /> -->
    </session-factory>
</hibernate-configuration>

当我点击 http://localhost:8080/traverse/adddummyvalue 时，我希望将一条新记录插入到表中但我得到了 MappingException。

Answer 1

您需要更改代码，因为您提到的示例适用于 Hibernate 4.3，而您正在使用 Hibernate 5.x。请参阅here进行解释。

按照 hibernate 5.x docs 更改代码

StandardServiceRegistry standardRegistry = new StandardServiceRegistryBuilder() .configure("hibernate.cfg.xml").build();
            Metadata metadata = new MetadataSources(standardRegistry).getMetadataBuilder().build();
            return metadata.getSessionFactoryBuilder().build();