老师看一下

package com.imooc.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;

public class MybatisUtils {
    private static SqlSessionFactory sqlSessionFactory = null;

    static{
        Reader reader = null;
        try {
            reader = Resources.getResourceAsReader("mybatis-config.xml");
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
        }catch(Exception e){
            e.printStackTrace();
            throw new ExceptionInInitializerError();
        }
    }

    public static SqlSession openSession(){
        return sqlSessionFactory.openSession(false);
    }
    public static void closeSession(SqlSession sqlSession){
        if (sqlSession != null) {
            sqlSession.close();
        }
    }
}

<?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>
        <setting name="mapUnderscoreToCamelCase" value="true"/>
    </settings>
    <environments default="stu">
        <environment id="stu">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/imooc?useUnicode=true&amp;characterEncoding=UTF-8"/>
                <property name="username" value="root"/>
                <property name="password" value="ccc980916"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="mappers/student.xml"/>
    </mappers>
</configuration>

package com.imooc.entity;

public class Student {
    private Integer id;
    private Integer regNo;
    private String name;
    private String sex;
    private Integer age;
    private String grade;
    private String major;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public Integer getregNo() {
        return regNo;
    }

    public void setRegNo(Integer regNo) {
        this.regNo = regNo;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public String getGrade() {
        return grade;
    }

    public void setGrade(String grade) {
        this.grade = grade;
    }

    public String getMajor() {
        return major;
    }

    public void setMajor(String major) {
        this.major = major;
    }
}

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="student">
    <select id="selectAll" resultType="com.imooc.entity.Student">
        select * from student order by reg_no;
    </select>

    <insert id="insert" parameterType="com.imooc.mybatis.entity">
        INSERT INTO student(reg_no,name,sex,age,grade,major)
        VALUES (#{regNo},#{name},#{sex},#{age},#{grade},#{major});
        <selectKey resultType="Integer" keyProperty="id" order="AFTER">
            select last_insert_id()
        </selectKey>
    </insert>
</mapper>

package com.imooc;


import com.imooc.entity.Student;
import com.imooc.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class WorkTest {
    @Test
    public void selectAll() throws Exception {
        SqlSession sqlSession = null;
        try {
            sqlSession = MybatisUtils.openSession();
            List<Student> list = sqlSession.selectList("student.selectAll");
            System.out.println("用户编号"+"  "+"学号"+"         "+"姓名"+"  "+"年龄"+"  "+"性别"+"  "+"年级"+"  "+"专业");
            for (Student s : list ){
                System.out.println(s.getId()+"        "+s.getregNo()+"   "+s.getName()+"   "+s.getAge()+"  "+s.getSex()+"  "+s.getGrade()+"  "+s.getMajor());
            }
        } catch (Exception e) {
            throw e;
        }finally{
            MybatisUtils.closeSession(sqlSession);
        }

    }

    @Test
    public void testInsert() throws Exception{
        SqlSession sqlSession = null;
        try {
            sqlSession = MybatisUtils.openSession();
            Student student = new Student();
            student.setRegNo(20171208);
            student.setName("言语");
            student.setSex("男");
            student.setAge(26);
            student.setGrade("2013");
            student.setMajor("哲学系");
            int num =sqlSession.insert("student.insert",student);
            sqlSession.commit();
        } catch (Exception e) {
            if(sqlSession != null){
                sqlSession.rollback();
            }
            throw e;
        }finally {
            MybatisUtils.closeSession(sqlSession);
        }

    }

}