报错：

BeanFactory not initialized or already closed - call 'refresh' before accessing beans via the ApplicationContext

原因：

使用ApplicationContext ac=new ClassPathXmlApplicationContext();的时候没有传递参数

改为

ApplicationContext ac=new ClassPathXmlApplicationContext("applicationContext.xml");

注意获取容器的时候一定要传递容器对应的配置文件

在applicationContext.xml中配置：

<!-- 配置dataSource -->
<bean name="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource">
    <property name="driverClass" value="com.mysql.cj.jdbc.Driver"/>
    <property name="jdbcUrl" value="jdbc:mysql://localhost:3306/ssm_spring?useUnicode=true&amp;characterEncoding=utf-8&amp;serverTimezone=GMT"/>
    <property name="user" value="root"/>
    <property name="password" value="root"/>
</bean>

<!-- 配置dao -->
<bean name="userDao" class="com.lingzhihao.dao.UserDaoImpl">
    <property name="dataSource" ref="dataSource"/>

</bean>
<!-- 配置service -->
<bean name="userService" class="com.lingzhihao.service.UserServiceImpl">
    <property name="ud" ref="userDao"/>
</bean>