一、报错问题

Caused by: java.lang.ClassNotFoundException: Could not load requested class : com.mysql.jdbc.Driver
在这里插入图片描述

二、问题背景

新建Java项目，并添加 Hibernate 框架支持，启动测试（运行默认的Main类中的main()方法），出现报错。

Main.java

import org.hibernate.HibernateException;
import org.hibernate.Metamodel;
import org.hibernate.query.Query;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

import javax.persistence.metamodel.EntityType;

import java.util.Map;

public class Main {
    
    
    private static final SessionFactory ourSessionFactory;

    static {
    
    
        try {
    
    
            Configuration configuration = new Configuration();
            configuration.configure();

            ourSessionFactory = configuration.buildSessionFactory();
        } catch (Throwable ex) {
    
    
            throw new ExceptionInInitializerError(ex);
        }
    }

    public static Session getSession() throws HibernateException {
    
    
        return ourSessionFactory.openSession();
    }

    public static void main(final String[] args) throws Exception {
    
    
        final Session session = getSession();
        try {
    
    
            System.out.println("querying all the managed entities...");
            final Metamodel metamodel = session.getSessionFactory().getMetamodel();
            for (EntityType<?> entityType : metamodel.getEntities()) {
    
    
                final String entityName = entityType.getName();
                final Query query = session.createQuery("from " + entityName);
                System.out.println("executing: " + query.getQueryString());
                for (Object o : query.list()) {
    
    
                    System.out.println("  " + o);
                }
            }
        } finally {
    
    
            session.close();
        }
    }
}