Caused by: java.lang.ClassNotFoundException: Could not load requested class : com.mysql.jdbc.Driver-Toy模板网

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一、报错问题

Caused by: java.lang.ClassNotFoundException: Could not load requested class : com.mysql.jdbc.Driver

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();
        }
    }
}

项目结构如下图所示：
caused by: java.lang.classnotfoundexception: could not load requested class,常见报错问题,java,mysql,hibernate

三、原因分析

缺少mysql对应版本的驱动包。

四、解决方案

步骤1：去官网下载对应版本的驱动，然后解压得到jar包（本文以下载5.1.47版本为例）

官网下载对应版本的驱动（jar包）地址：https://downloads.mysql.com/archives/c-j/

caused by: java.lang.classnotfoundexception: could not load requested class,常见报错问题,java,mysql,hibernate

下载后的文件：mysql-connector-java-5.1.47.zip
caused by: java.lang.classnotfoundexception: could not load requested class,常见报错问题,java,mysql,hibernate

解压文件，得到jar包：mysql-connector-java-5.1.47.jar

caused by: java.lang.classnotfoundexception: could not load requested class,常见报错问题,java,mysql,hibernate

步骤2：将 jar 包导入项目

caused by: java.lang.classnotfoundexception: could not load requested class,常见报错问题,java,mysql,hibernate

选择 mysql-connector-java-5.1.47.jar，如下图所示。
caused by: java.lang.classnotfoundexception: could not load requested class,常见报错问题,java,mysql,hibernate

添加 mysql-connector-java-5.1.47.jar 之后，如下图所示。然后点击“OK”按钮即可。
caused by: java.lang.classnotfoundexception: could not load requested class,常见报错问题,java,mysql,hibernate 文章来源地址https://www.toymoban.com/news/detail-784092.html

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