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

缺乏、安全感 2023-10-10 19:06 114阅读 0赞

# 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][657f041af8f04a6d9dcbbe141209ee5d.png]

# 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：  
![在这里插入图片描述][424583b23cf04a91ae0d318bad3b3813.png]

# 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/][https_downloads.mysql.com_archives_c-j]

![在这里插入图片描述][59d4133d0d1a4c549ef5cf8bdaeae5b7.png]

下载后的文件：mysql-connector-java-5.1.47.zip  
![在这里插入图片描述][6980fed3f9414e70a1c9f7a2b45b9669.png]

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

![在这里插入图片描述][95eaf33fd54b4669957229a7df731d98.png]

#### 步骤2：将 jar 包导入项目 ####

![在这里插入图片描述][d9160a2b4be84c6c91b726a7e3d2022c.png]

![在这里插入图片描述][2da89340a5574df898dc4a02fe7e33ab.png]

选择 mysql-connector-java-5.1.47.jar，如下图所示。  
![在这里插入图片描述][f7da103f1ad44da5895041fd75e33fab.png]

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。  
![在这里插入图片描述][3d9347b7a8374a6bb743ec531482b87f.png]

[657f041af8f04a6d9dcbbe141209ee5d.png]: https://img-blog.csdnimg.cn/657f041af8f04a6d9dcbbe141209ee5d.png
[424583b23cf04a91ae0d318bad3b3813.png]: https://img-blog.csdnimg.cn/424583b23cf04a91ae0d318bad3b3813.png
[https_downloads.mysql.com_archives_c-j]: https://downloads.mysql.com/archives/c-j/
[59d4133d0d1a4c549ef5cf8bdaeae5b7.png]: https://img-blog.csdnimg.cn/59d4133d0d1a4c549ef5cf8bdaeae5b7.png
[6980fed3f9414e70a1c9f7a2b45b9669.png]: https://img-blog.csdnimg.cn/6980fed3f9414e70a1c9f7a2b45b9669.png
[95eaf33fd54b4669957229a7df731d98.png]: https://img-blog.csdnimg.cn/95eaf33fd54b4669957229a7df731d98.png
[d9160a2b4be84c6c91b726a7e3d2022c.png]: https://img-blog.csdnimg.cn/d9160a2b4be84c6c91b726a7e3d2022c.png
[2da89340a5574df898dc4a02fe7e33ab.png]: https://img-blog.csdnimg.cn/2da89340a5574df898dc4a02fe7e33ab.png
[f7da103f1ad44da5895041fd75e33fab.png]: https://img-blog.csdnimg.cn/f7da103f1ad44da5895041fd75e33fab.png
[3d9347b7a8374a6bb743ec531482b87f.png]: https://img-blog.csdnimg.cn/3d9347b7a8374a6bb743ec531482b87f.png