Hibernate中乐观锁的实现示例

<!DOCTYPE hibernate-configuration PUBLIC
        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
        "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
    <session-factory>
        <!-- 数据库连接配置 -->
        <property name="hibernate.connection.driver_class">com.mysql.cj.jdbc.Driver</property>
        <property name="hibernate.connection.url">jdbc:mysql://localhost:3306/your_database</property>
        <property name="hibernate.connection.username">your_username</property>
        <property name="hibernate.connection.password">your_password</property>

        <!-- Hibernate 属性配置 -->
        <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
        <property name="hibernate.show_sql">true</property>
        <property name="hibernate.format_sql">true</property>
        <property name="hibernate.hbm2ddl.auto">update</property>

        <!-- 映射类配置 -->
        <mapping class="com.example.domain.Student"/>
    </session-factory>
</hibernate-configuration>

import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

public class HibernateUtil {
    private static final SessionFactory sessionFactory;

    static {
        try {
            // 从配置文件创建SessionFactory
            sessionFactory = new Configuration().configure("hibernate.cfg.xml").buildSessionFactory();
        } catch (Throwable ex) {
            // 记录启动失败的错误
            System.err.println("Initial SessionFactory creation failed." + ex);
            throw new ExceptionInInitializerError(ex);
        }
    }

    public static SessionFactory getSessionFactory() {
        return sessionFactory;
    }
}

package com.example.domain;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Version;

@Entity
public class Student {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    
    private String name;
    private int age;

    @Version
    private int version;

    public Student() {}

    public Student(String name, int age) {
        this.name = name;
        this.age = age;
    }

    // getters 和 setters
    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public int getVersion() {
        return version;
    }

    public void setVersion(int version) {
        this.version = version;
    }
}

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;

public class HibernateOptimisticLockingExample {
    public static void main(String[] args) {
        // 获取SessionFactory
        SessionFactory sessionFactory = HibernateUtil.getSessionFactory();
        
        // 第一个会话
        Session session1 = sessionFactory.openSession();
        Transaction transaction1 = session1.beginTransaction();
        
        // 第二个会话
        Session session2 = sessionFactory.openSession();
        Transaction transaction2 = session2.beginTransaction();

        try {
            // 在第一个会话中获取对象
            Student student1 = session1.get(Student.class, 1L);
            System.out.println("Session1 - Student: " + student1.getName() + ", Age: " + student1.getAge() + ", Version: " + student1.getVersion());

            // 在第二个会话中获取相同的对象
            Student student2 = session2.get(Student.class, 1L);
            System.out.println("Session2 - Student: " + student2.getName() + ", Age: " + student2.getAge() + ", Version: " + student2.getVersion());

            // 修改并更新对象
            student1.setAge(21);
            session1.update(student1);
            transaction1.commit();
            System.out.println("Session1 - Updated Student: " + student1.getName() + ", Age: " + student1.getAge() + ", Version: " + student1.getVersion());

            // 尝试在第二个会话中提交修改
            student2.setAge(22);
            session2.update(student2);
            transaction2.commit(); // 这里会抛出异常，因为版本号不一致

        } catch (Exception e) {
            if (transaction2 != null) {
                transaction2.rollback();
            }
            e.printStackTrace();
        } finally {
            if (session1 != null) {
                session1.close();
            }
            if (session2 != null) {
                session2.close();
            }
        }

        // 关闭SessionFactory
        sessionFactory.close();
    }
}