Hibernate 5:-org.hibernate.MappingException:未知实体

2022-01-30 00:00:00 mysql java Hibernate hibernate-5.x

当我尝试将 hibernate 5.0 与 mysql 集成时，我收到错误消息 org.hibernate.MappingException: Unknown entity

I am getting the error message org.hibernate.MappingException: Unknown entity when i am trying to integrate hibernate 5.0 with mysql

这似乎是 hibernate5.0.0 和 5.0.1 的问题.这适用于休眠 4.3.9

This seems to be an issue with hibernate5.0.0 and 5.0.1 . This works fine with hibernate 4.3.9

<dependency>
    <groupId>org.hibernate</groupId>
        <artifactId>hibernate-core</artifactId>
        <version>5.0.0.Final</version>
    </dependency>
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>5.1.36</version>
</dependency>

hibernate.cfg.xml

<session-factory>

    <!-- Database connection settings -->
    <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
    <property name="connection.url">jdbc:mysql://localhost:3307/SampleDB
    </property>
    <property name="connection.username">root</property>
    <property name="connection.password"></property>

    <!-- JDBC connection pool (use the built-in) -->
    <property name="connection.pool_size">1</property>
    <property name="dialect">org.hibernate.dialect.MySQLDialect</property>

    <!-- Echo all executed SQL to stdout -->
    <property name="show_sql">true</property>

    <!-- Drop and re-create the database schema on startup -->
    <property name="hbm2ddl.auto">create</property>

    <mapping class="UserA.User"></mapping>

</session-factory>


package UserA;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.Configuration;
import org.hibernate.mapping.Map;
import org.hibernate.metadata.ClassMetadata;
import org.hibernate.persister.entity.EntityPersister;
import org.hibernate.service.ServiceRegistry;

public class HibernateMain {

    public static void main(String[] args) {

        Configuration configuration = new Configuration();
        configuration.configure();
        ServiceRegistry sr = new StandardServiceRegistryBuilder().applySettings(configuration.getProperties()).build();

        SessionFactory sf = configuration.buildSessionFactory(sr);




        User user1 = new User();
        user1.setUserName("Arpit");
        user1.setUserMessage("Hello world from arpit");
        user1.setUserId(22);

        Session ss = sf.openSession();
        ss.beginTransaction();
        // saving objects to session
        ss.save(user1);
        ss.getTransaction().commit();
        ss.close();

    }

}

用户.java

package UserA;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;

@Entity(name="User_table")
public class User {
    @Id
    int userId;
    @Column(name = "User_Name")
    String userName;

    @Column(name = "User_Message")
    String userMessage;

    public int getUserId() {
        return userId;
    }

    public void setUserId(int userId) {
        this.userId = userId;
    }

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public String getUserMessage() {
        return userMessage;
    }

    public void setUserMessage(String userMessage) {
        this.userMessage = userMessage;
    }

}

推荐答案

我已经修复了与 Hibernate 5 相同的问题.这段代码有问题

I have fixed the same issue with Hibernate 5. There is a problem in this code

Configuration configuration = new Configuration();
configuration.configure();

ServiceRegistry sr = new StandardServiceRegistryBuilder().applySettings(
    configuration.getProperties()).build();

SessionFactory sf = configuration.buildSessionFactory(sr);

此代码适用于 Hibernate 4.3.5，但相同的代码在 Hibernate 5 中存在相同的问题.

This code works fine for Hibernate 4.3.5, but the same code has the same issue for Hibernate 5.

当您使用 Hibernate 5 执行 configuration.buildSessionFactory(sr) 时，Configuration 会丢失通过调用 configuration.configure().

When you do configuration.buildSessionFactory(sr), using Hibernate 5, Configuration losts all information about mapping that gets by call configuration.configure().

解决方案

为了解决这个问题，如果你使用标准配置文件hibernate.cfg.xml和hibernate.properties，你可以通过这种方式创建会话工厂(没有<代码>ServiceRegistry)

To fix the issue, if you use standard configuration files hibernate.cfg.xml and hibernate.properties, you can create the session factory by this way (without ServiceRegistry) 

SessionFactory sessionFactory = new Configuration().configure().buildSessionFactory();

加载属性

如果您在 hibernate.properties 以外的文件中有属性，则可以使用 StandardServiceRegistryBuilder 构建会话工厂(无论如何，如果您有 hibernate.properties 和其他文件，它将同时加载)

If you have properties in a file other then hibernate.properties, you can build session factory using StandardServiceRegistryBuilder (anyway, if you have hibernate.properties and other file, it will be loaded both)

将属性作为资源加载

ServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder().
    configure().loadProperties("hibernate-h2.properties").build();
SessionFactory sf = new Configuration().buildSessionFactory(serviceRegistry);

您需要在类路径(源文件夹的根目录，资源文件夹)中有 hibernate-h2.properties.您也可以从根源文件夹指定路径/com/github/xxx/model/hibernate-h2.properties.

You need to have hibernate-h2.properties in the class path (root of the sources folder, resources folder). You can specify a path from the root source folder too /com/github/xxx/model/hibernate-h2.properties.

从文件系统中的路径加载属性

To load properties from a path in the file system

File propertiesPath = new File("some_path");
ServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder().
    configure().loadProperties(propertiesPath).build();
SessionFactory sf = new Configuration().buildSessionFactory(serviceRegistry);

您可以在此处找到使用此方法的示例控制台应用程序 fluent-hibernate-mysql.它使用实用程序类从 fluent-hibernate 库构建会话工厂.

You can find an example console application using this approach here fluent-hibernate-mysql. It uses a utility class to build the session factory from the fluent-hibernate library.

Hibernate 5 教程不正确

Hibernate 5 教程中有一个不正确的例子 1.1.6.启动和助手.它使用此代码

There is an incorrect example in Hibernate 5 tutorial 1.1.6. Startup and helpers. It uses this code

 return new Configuration().configure().buildSessionFactory(
                new StandardServiceRegistryBuilder().build() );

它没有进行正确的配置.

It doesn't do a proper configuration.

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