不知道是哪里出了错误，自己排查了好久还是找不出来

package com.imooc.student;

import com.imooc.student.entity.Classes1;
import com.imooc.student.utils.StudentUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class Students1Testor {
@Test
    public void testOneToMany() throws Exception{
        SqlSession session=null;
try{
            session= StudentUtils.openSession();
            List<Classes1> list=session.selectList("classes1.selectOneToMany","一班");
for(Classes1 c:list){
                System.out.println(c.getName()+"  "+c.getStudents1s().toString());
            }
        }catch (Exception e){
throw e;
        }finally {
            StudentUtils.closeSession(session);
        }
    }
}

package com.imooc.student.entity;

import java.util.List;

public class Classes1 {
private Integer id;
private String classNo;
private String name;
private String major;
private List<Students1> students1s;

public List<Students1> getStudents1s() {
return students1s;
    }

public void setStudents1s(List<Students1> students1s) {
this.students1s = students1s;
    }

public Integer getId() {
return id;
    }

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

public String getClassNo() {
return classNo;
    }

public void setClassNo(String classNo) {
this.classNo = classNo;
    }

public String getName() {
return name;
    }

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

public String getMajor() {
return major;
    }

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

package com.imooc.student.entity;

public class Students1 {
private Integer id;
private String stuNo;
private String stuName;
private String sex;
private String classNo;
private Classes1 classes1;

public Integer getId() {
return id;
    }

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

public String getStuNo() {
return stuNo;
    }

public void setStuNo(String stuNo) {
this.stuNo = stuNo;
    }

public String getStuName() {
return stuName;
    }

public void setStuName(String stuName) {
this.stuName = stuName;
    }

public String getSex() {
return sex;
    }

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

public String getClassNo() {
return classNo;
    }

public void setClassNo(String classNo) {
this.classNo = classNo;
    }

public Classes1 getClasses1() {
return classes1;
    }

public void setClasses1(Classes1 classes1) {
this.classes1 = classes1;
    }
}

<?xml version="1.0" encoding="Utf-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="students1">
<select id="selectByClassNo" parameterType="String" resultType="com.imooc.student.entity.Students1">
        select * from students1 where class_no=#{value}
    </select>
</mapper>

<?xml version="1.0" encoding="Utf-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="classes1">
<resultMap id="rmClasses1" type="com.imooc.student.entity.Classes1">
<id column="id" property="id"/>
<result column="class_no" property="classNo"/>
<collection property="students1" select="selectByClassNo" column="class_no"></collection>
</resultMap>
<select id="selectOneToMany" resultMap="rmClasses1">
        select * from classes1 where name=#{value}
    </select>
</mapper>

<?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="dev">
<!--配置环境,不同的环境不同的id名字,名字最好是有意义的-->
        <environment id="dev">
<!--采用JDBC方式对数据库事物进行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.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="154672"/>
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="mappers/goods.xml"/>
<mapper resource="mappers/student.xml"/>
<mapper resource="mappers/goods_detail.xml"/>
<mapper resource="mappers/classes1.xml"/>
<mapper resource="mappers/students1.xml"/>
</mappers>
</configuration>

package com.imooc.student.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 StudentUtils {
private static SqlSessionFactory sqlSessionFactory = null;

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

public static SqlSession openSession(){
return sqlSessionFactory.openSession();
    }

public static void closeSession(SqlSession session){
if(session!=null){
            session.close();
        }
    }
}

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