为什么我用junit写单元测试，Rollback没有用，数据库不会回滚

package cn.edu.zjweu.StudentAdmin.Dao;

import cn.edu.zjweu.StudentAdmin.User.User;
import cn.edu.zjweu.StudentAdmin.Util.DbUtil;
import org.junit.Assert;
import org.junit.Test;
import java.sql.Connection;

import org.springframework.transaction.annotation.Transactional;
import org.springframework.test.annotation.Rollback;
import static org.hamcrest.Matchers.is;

public class UserDaoTest {
UserDao userDao = new UserDao();

      @Test
@Transactional
@Rollback(true)
public void testDelete() throws Exception {
    Connection con=null;
    DbUtil dbUtil= new DbUtil();
    con=dbUtil.getCon();
    boolean result = userDao.delete(con, "32");
    Assert.assertEquals(false, result);
}
}

这里有很详细的描述

https://docs.spring.io/spring-framework/docs/4.2.x/spring-framework-reference/html/transaction.html

简单地说, 如果你用JDBC数据连接, 又想让spring来管理事务, 那个你的连接需要用

org.springframework.jdbc.datasource.DataSourceUtils 来获得

如这个样子

 Connection conn = DataSourceUtils.getConnection(dataSource);

并且要声明事务管理类

 <bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close">
    <property name="driverClassName" value="${jdbc.driverClassName}" />
    <property name="url" value="${jdbc.url}" />
    <property name="username" value="${jdbc.username}" />
    <property name="password" value="${jdbc.password}" />
</bean>


<bean id="txManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
    <property name="dataSource" ref="dataSource"/>
</bean>

当你用自定义的DBUtil获取数据库连接时, spring不能干预事务, 自然也就无法回滚了.