Hibernate - ClassNotFoundException：com.mysql.jdbc.Driver [英] Hibernate - ClassNotFoundException: com.mysql.jdbc.Driver

问题描述

 我试图通过Hibernate从MySQL数据库检索数据，但是我遇到了这个错误：无法创建sessionFactory object.org.hibernate.service.classloading.spi.ClassLoadingException：指定的JDBC驱动程序无法加载com.mysql.jdbc.Driver 
 
 java.lang.ClassNotFoundException：无法加载请求class：com.mysql.jdbc.Driver 
 [...] 
  

我使用这个类名为DAOFactory来获得hibernate会话：

pre $ public $ DA $ a
$ b $ private static boolean isInstance =假;
private static SessionFactory sessionFactory;
private static ServiceRegistry serviceRegistry;
私有静态会话会话;

private DAOFactory（）抛出ExceptionInInitializerError {
if（！isInstance）{
try {
Configuration cfg = new Configuration（）。configure（）;
serviceRegistry = new ServiceRegistryBuilder（）。applySettings（cfg.getProperties（））
.buildServiceRegistry（）;
sessionFactory = cfg.buildSessionFactory（serviceRegistry）;
} catch（Throwable ex）{
System.err.println（Failed to create sessionFactory object。+ ex）;
抛出新的ExceptionInInitializerError（ex）;
}
session = sessionFactory.openSession（）;
isInstance = true;



public static DAOFactory getInstance（）{
return new DAOFactory（）;
}

public Session getSession（）{
return session;

hibernate.cfg.xml：

 <？xml version =1.0encoding =UTF-8？> 
<！DOCTYPE hibernate-configuration PUBLIC -  // Hibernate / Hibernate配置DTD 3.0 // EN
http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd > 
< hibernate-configuration> 
< session-factory name => 
< property name =connection.driver_class> com.mysql.jdbc.Driver< / property> 
< property name =connection.url> jdbc：mysql：// localhost：3306 / enigma< / property> 
< property name =connection.username> root< / property> 
< property name =connection.password>< / property> 
< property name =dialect> org.hibernate.dialect.MySQLDialect< / property> 
< property name =connection.pool_size> 1< / property> 
< property name =current_session_context_class>线程< / property> 
< property name =cache.provider_class> org.hibernate.cache.NoCacheProvider< / property> 
< property name =show_sql> true< / property> 
< property name =hbm2ddl.auto>更新< / property> 
< / session-factory> 
< / hibernate-configuration> 
  

和 mysql-connector-java-5.1.26-bin.jar 已经在类路径中：

有人看到我缺少的东西吗？

解决方案

感谢Reimeus的回答。 mysql-connector-java-5.1.26-bin.jar 需要在运行时类路径中。

运行 - >运行配置... - >类路径 - >添加外部JAR。

清理所有内容，再试一次，异常消失。

I'm trying to retrieve data from a MySQL database through Hibernate, but I'm stuck with this error:

Failed to create sessionFactory object.org.hibernate.service.classloading.spi.ClassLoadingException: Specified JDBC Driver com.mysql.jdbc.Driver could not be loaded

java.lang.ClassNotFoundException: Could not load requested class : com.mysql.jdbc.Driver
[...]

I use a class called DAOFactory to get the hibernate session:

public class DAOFactory {

    private static boolean isInstance = false;  
    private static SessionFactory sessionFactory;
    private static ServiceRegistry serviceRegistry; 
    private static Session session;

    private DAOFactory() throws ExceptionInInitializerError{        
        if( !isInstance ) {
            try {               
                Configuration cfg   = new Configuration().configure();              
                serviceRegistry     = new ServiceRegistryBuilder().applySettings(cfg.getProperties())
                                                .buildServiceRegistry();
                sessionFactory      = cfg.buildSessionFactory(serviceRegistry);
            } catch (Throwable ex) {
                System.err.println("Failed to create sessionFactory object."+ ex);
                throw new ExceptionInInitializerError(ex);
            }
            session = sessionFactory.openSession();         
            isInstance = true ;
        }               
    }

    public static DAOFactory getInstance() {        
        return new DAOFactory() ;
    }

    public Session getSession() {
        return session ;
    }
}

hibernate.cfg.xml:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
                                         "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
    <session-factory name="">
        <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="connection.url">jdbc:mysql://localhost:3306/enigma</property>
        <property name="connection.username">root</property>
        <property name="connection.password"></property>
        <property name="dialect">org.hibernate.dialect.MySQLDialect</property>
        <property name="connection.pool_size">1</property>
        <property name="current_session_context_class">thread</property>
        <property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>
        <property name="show_sql">true</property>
        <property name="hbm2ddl.auto">update</property>
    </session-factory>
</hibernate-configuration>

And mysql-connector-java-5.1.26-bin.jar is already in the classpath:

Does anyone see what I'm missing ?

解决方案

Thanks to Reimeus for the answer. mysql-connector-java-5.1.26-bin.jar needs to be in the runtime classpath.

Run -> Run Configurations... -> Classpath -> Add external JAR.

Clean everything, try again, and the Exception is gone.

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