Mybatis注解批量插入数据报空指针异常

TeacherDAO

package com.imooc.mybatis.dao;

import com.imooc.mybatis.entity.Teacher;

import org.apache.ibatis.annotations.Insert;

import org.apache.ibatis.annotations.Param;

import org.apache.ibatis.annotations.SelectKey;

import java.util.List;

public interface TeacherDAO {

    @Insert({

            "<script>",

            "insert into teacher (name,sex,j_no,subject,grade,description) values",

            "<foreach collection='list' item='item' index='index' separator=','>",

            "(#{item.name},#{item.sex},#{item.jNo},#{item.subject},#{item.grade},#{item.description})",

            "</foreach>",

            "</script>"

    })

    @SelectKey(statement = "select last_insert_id()", before = false ,keyProperty = "id" ,resultType = Integer.class)

    public int batchInsert(@Param("list") List<Teacher> list);

}

mybatis-config.xml

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE configuration

        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"

        "http://mybatis.org/dtd/mybatis-3-config.dtd">

<configuration>

    <settings>

        <!-- goods_id ==> goodsId 驼峰命名转换 -->

        <setting name="mapUnderscoreToCamelCase" value="true"/>

    </settings>

    <!--设置默认指向的数据库-->

    <environments default="c3p0_dev ">

        <!--配置环境，不同的环境不同的id名字-->

        <environment id="dev">

            <!-- 采用JDBC方式对数据库事务进行commit/rollback -->

            <transactionManager type="JDBC"></transactionManager>

            <!--采用连接池方式管理数据库连接-->

            <dataSource type="POOLED">

                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>

                <property name="url" value="jdbc:mysql://localhost:3306/babytun?useUnicode=true&amp;characterEncoding=UTF-8"/>

                <property name="username" value="root"/>

                <property name="password" value="wrx199704"/>

            </dataSource>

        </environment>

        <environment id="c3p0_dev">

            <transactionManager type="JDBC"></transactionManager>

            <dataSource type="com.imooc.mybatis.datasource.C3P0DataSourceFactory">

                <property name="driverClass" value="com.mysql.jdbc.Driver"/>

                <property name="jdbcUrl" value="jdbc:mysql://localhost:3306/babytun?useUnicode=true&amp;characterEncoding=UTF-8"/>

                <property name="user" value="root"/>

                <property name="password" value="wrx199704"/>

                <property name="initialPoolSize" value="5"/>

                <property name="maxPoolSize" value="20"/>

                <property name="minPoolSize" value="5"/>

            </dataSource>

        </environment>

    </environments>

    <mappers>

<!--        <mapper class="com.imooc.mybatis.dao.GoodsDAO"></mapper>-->

        <package name="com.imooc.mybatis.dao"/>

    </mappers>

</configuration>

MybatisUtils

package com.imooc.mybatis.utils;

import org.apache.ibatis.io.Resources;

import org.apache.ibatis.session.SqlSession;

import org.apache.ibatis.session.SqlSessionFactory;

import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import java.io.IOException;

import java.io.Reader;

/**

 * MyBatisUtils工具类,创建全局唯一的SqlSessionFactory对象

 */

public class MyBatisUtils {

    //利用static(静态)属于类不属于对象,且全局唯一

    private static SqlSessionFactory sqlSessionFactory = null;

    //利用静态块在初始化类时实例化sqlSessionFactory

    static {

        Reader reader = null;

        try {

            reader = Resources.getResourceAsReader("mybatis-config.xml");

            sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);

        } catch (IOException e) {

            e.printStackTrace();

            //初始化错误时,通过抛出异常ExceptionInInitializerError通知调用者

            throw new ExceptionInInitializerError(e);

        }

    }

    /**

     * openSession 创建一个新的SqlSession对象

     * @return SqlSession对象

     */

    public static SqlSession openSession(){

        //默认SqlSession对自动提交事务数据(commit)

        //设置false代表关闭自动提交,改为手动提交事务数据

        return sqlSessionFactory.openSession(false);

    }

    /**

     * 释放一个有效的SqlSession对象

     * @param session 准备释放SqlSession对象

     */

    public static void closeSession(SqlSession session){

        if(session != null){

            session.close();

        }

    }

}

JUNITTest

@Test

public void testTeacherBatchInsert(){

    SqlSession session = null;

    try {

        session = MyBatisUtils.openSession();

        TeacherDAO teacherDAO = session.getMapper(TeacherDAO.class);

        List list = new ArrayList();

        for(int i=0;i<500;i++){

            Teacher t = new Teacher();

            t.setName("测试名字" + i);

            t.setSex(i%2 == 0 ? "男" : "女");

            t.setjNo(i+100);

            t.setSubject(i%2 == 0 ? "语文" : "数学");

            t.setGrade(i % 6 + "年级");

            t.setDescription("测试备注" + i);

            list.add(t);

        }

        int num = teacherDAO.batchInsert(list);

        session.commit();

        System.out.println("更新了" + num + "条数据");

    } catch (Exception e){

        e.printStackTrace();

    } finally {

        MyBatisUtils.closeSession(session);

    }

}

报错信息：