Mybatis查询mysql延时加载操作（18）

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Mybatis查询mysql延时加载操作。采用教师和课程一对一关系演示延时加载操作应用。

1、采用延时加载，需要在工程配置文件

工程主 mapper.xml 文件，mybatis-03.xml 中开启延迟加载配置，关闭立即加载设置

2、主mapper.xml 文件，既：teacherMapper.xml

2.1 teacherMapper.xml 文件

 <!-- 延时加载 -->
    <select id="queryTeacherInfoWithResultMapByCourseNo2" parameterType="int" resultMap="teacher_course_lazy_load_map">
        SELECT * FROM teacher
</select>
    <resultMap id="teacher_course_lazy_load_map" type="com.mybatis03.bean.Teacher">
        <!-- 老师信息 -->
        <id property="teaNo" column="teano"/>
        <result property="courseNo" column="courseno"/>
        <result property="teaName" column="teaname"/>
        <association property="teacherCourse" javaType="com.mybatis03.bean.TeacherCourse"
                     select="com.mybatis03.mapper.TeacherCourseMapper.queryTeacherCourseByID" column="courseno">
        </association>
    </resultMap>

teacherMapper.xml配置文件说明

教师与课程一对一关系需要借助<association>标签

1）、采用延迟加载时 ,延迟子查询语句需要写在标签中（既：需要写在 <association>标签中而不是标签体内），参照上图；

2）、通过 <select>中属性esultMap的value值 teacher_course_lazy_load_map 与 <resultmap>标签的id一一对应且在此配置中存在唯一性即可；

3）、<resultmap>标签中的type为最终返回的结果集；

4）、<resultmap>标签中包含teacher属性。property对应teacher实体类的属性，culumn对应数据库中的字段值；

5）、<association>标签中select为引用了外标签查询，column为teacher实体类查询（主查询）与子查询（查询教师课程的 select标签）关联编号；

2.2 子查询xml文件，既：teacherMapper.xml 文件中子查询文件

<?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="com.mybatis03.mapper.TeacherCourseMapper">
    <!-- 查询教师课程，延迟加载应用此配置文件 -->
    <!-- 查询教师对应的课程 -->
    <select id="queryTeacherCourseByID" parameterType="int" resultType="com.mybatis03.bean.TeacherCourse">
        SELECT * FROM teachercourse WHERE courseno = #{courseno}
    </select>
</mapper>

3、实体类

3.1 教师实体类

package com.mybatis03.bean;
public class Teacher {
    @Override
    public String toString() {
        return "Teacher{" +
                "teaNo=" + teaNo +
                ", courseNo=" + courseNo +
                ", teaName='" + teaName + '\'' +
                ", teacherCourse{" +

                "courseNo=" + teacherCourse.getCourseNo() +
                ", courseName=" + teacherCourse.getCourseName() +"}"+

                '}';
    }


    /* 教师编号 */
    private int teaNo;
    /* 课程编号 */
    private int courseNo;
    /* 教师名称 */
    private String teaName;

    /* 教师课程类,课程作为老师属性 */
    private TeacherCourse teacherCourse;

    /* 新增一个教研组编号，用于关联教研组编号，实现多对一关联*/
    private int  groupNo;

    /**
     *  <!--利用resultMap实现一对一 -->
     * @return
     */
    public TeacherCourse getTeacherCourse() {
        return teacherCourse;
    }

    public void setTeacherCourse(TeacherCourse teacherCourse) {
        this.teacherCourse = teacherCourse;
    }

    public int getGroupNo() {
        return groupNo;
    }

    public void setGroupNo(int groupNo) {
        this.groupNo = groupNo;
    }

    public int getCourseNo() {
        return courseNo;
    }

    public void setCourseNo(int courseNo) {
        this.courseNo = courseNo;
    }

    public int getTeaNo() {
        return teaNo;
    }

    public void setTeaNo(int teaNo) {
        this.teaNo = teaNo;
    }

    public String getTeaName() {
        return teaName;
    }

    public void setTeaName(String teaName) {
        this.teaName = teaName;
    }
}

3.2 教师对应课程实体类

public class TeacherCourse {

    /* 课程编号 */
    private int courseNo;
    /* 课程名称 */
    private String courseName;

    public int getCourseNo() {
        return courseNo;
    }

    public void setCourseNo(int courseNo) {
        this.courseNo = courseNo;
    }

    public String getCourseName() {
        return courseName;
    }

    public void setCourseName(String courseName) {
        this.courseName = courseName;
    }


    @Override
    public String toString() {
        return "TeacherCourse{" +
                "courseNo=" + courseNo +
                ", courseName='" + courseName + '\'' +
                '}';
    }
}

4、查询接口类

public interface TeacherMapper {
    /* 查询全部学生然后做延迟加载  */
    List<Teacher>  queryTeacherInfoWithResultMapByCourseNo2();
}

5、测试类

 /*  查询全部学生然后做延迟加载 */
    @Test
    public void queryTeacherInfoWithResultMapByCourseNo2() throws Exception {
        Reader reader = Resources.getResourceAsReader("mybatis-03.xml");
        SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(reader);

        SqlSession session = sessionFactory.openSession();
        TeacherMapper personMapper = session.getMapper(TeacherMapper.class);
        List<Teacher> teacherList = personMapper.queryTeacherInfoWithResultMapByCourseNo2();

        for (Teacher teacher : teacherList){
            System.out.println("教师编号："+teacher.getTeaNo()+",教师名称："+teacher.getTeaName()+","+
                            "教师课程编号:"+teacher.getCourseNo());
            // 获得教师课程信息
            TeacherCourse teacherCourse = teacher.getTeacherCourse();
            System.out.println("教师对应课程信息：["+"课程编号="+teacherCourse.getCourseNo()+",课程名称"+teacherCourse.getCourseName()+"]");
        }
        //System.out.println("查询全部学生然后做延迟加载,查询结果为：" + teacherList);
    }

6、数据库数据

6.1 教师数据库表信息

6.2 教师对应课程数据库结构和对应数据

7、测试结果

[lsjSso]2021-10-19 22:57:30,277-org.apache.ibatis.transaction.jdbc.JdbcTransaction-9653[main]DEBUGorg.apache.ibatis.transaction.jdbc.JdbcTransaction-Opening JDBC Connection
[lsjSso]2021-10-19 22:57:30,804-org.apache.ibatis.datasource.pooled.PooledDataSource-10180[main]DEBUGorg.apache.ibatis.datasource.pooled.PooledDataSource-Created connection 1443967876.
[lsjSso]2021-10-19 22:57:30,804-org.apache.ibatis.transaction.jdbc.JdbcTransaction-10180[main]DEBUGorg.apache.ibatis.transaction.jdbc.JdbcTransaction-Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@56113384]
[lsjSso]2021-10-19 22:57:30,811-com.mybatis03.mapper.TeacherMapper.queryTeacherInfoWithResultMapByCourseNo2-10187[main]DEBUGcom.mybatis03.mapper.TeacherMapper.queryTeacherInfoWithResultMapByCourseNo2-==>  Preparing: SELECT * FROM teacher 
[lsjSso]2021-10-19 22:57:31,026-com.mybatis03.mapper.TeacherMapper.queryTeacherInfoWithResultMapByCourseNo2-10402[main]DEBUGcom.mybatis03.mapper.TeacherMapper.queryTeacherInfoWithResultMapByCourseNo2-==> Parameters: 
[lsjSso]2021-10-19 22:57:31,302-com.mybatis03.mapper.TeacherMapper.queryTeacherInfoWithResultMapByCourseNo2-10678[main]DEBUGcom.mybatis03.mapper.TeacherMapper.queryTeacherInfoWithResultMapByCourseNo2-<==      Total: 4
[lsjSso]2021-10-19 22:57:50,467-com.mybatis03.mapper.TeacherCourseMapper.queryTeacherCourseByID-29843[main]DEBUGcom.mybatis03.mapper.TeacherCourseMapper.queryTeacherCourseByID-==>  Preparing: SELECT * FROM teachercourse WHERE courseno = ? 
[lsjSso]2021-10-19 22:57:50,468-com.mybatis03.mapper.TeacherCourseMapper.queryTeacherCourseByID-29844[main]DEBUGcom.mybatis03.mapper.TeacherCourseMapper.queryTeacherCourseByID-==> Parameters: 7001(Integer)
[lsjSso]2021-10-19 22:57:50,468-com.mybatis03.mapper.TeacherCourseMapper.queryTeacherCourseByID-29844[main]DEBUGcom.mybatis03.mapper.TeacherCourseMapper.queryTeacherCourseByID-<==      Total: 1
教师编号：1001,教师名称：sara,教师课程编号:7001
教师对应课程信息：[课程编号=7001,课程名称chinese]
[lsjSso]2021-10-19 22:58:42,576-com.mybatis03.mapper.TeacherCourseMapper.queryTeacherCourseByID-81952[main]DEBUGcom.mybatis03.mapper.TeacherCourseMapper.queryTeacherCourseByID-==>  Preparing: SELECT * FROM teachercourse WHERE courseno = ? 
[lsjSso]2021-10-19 22:58:42,576-com.mybatis03.mapper.TeacherCourseMapper.queryTeacherCourseByID-81952[main]DEBUGcom.mybatis03.mapper.TeacherCourseMapper.queryTeacherCourseByID-==> Parameters: 7002(Integer)
[lsjSso]2021-10-19 22:58:42,577-com.mybatis03.mapper.TeacherCourseMapper.queryTeacherCourseByID-81953[main]DEBUGcom.mybatis03.mapper.TeacherCourseMapper.queryTeacherCourseByID-<==      Total: 1
教师编号：1002,教师名称：sakula,教师课程编号:7002
教师对应课程信息：[课程编号=7002,课程名称english]
[lsjSso]2021-10-19 22:58:56,555-com.mybatis03.mapper.TeacherCourseMapper.queryTeacherCourseByID-95931[main]DEBUGcom.mybatis03.mapper.TeacherCourseMapper.queryTeacherCourseByID-==>  Preparing: SELECT * FROM teachercourse WHERE courseno = ? 
[lsjSso]2021-10-19 22:58:56,555-com.mybatis03.mapper.TeacherCourseMapper.queryTeacherCourseByID-95931[main]DEBUGcom.mybatis03.mapper.TeacherCourseMapper.queryTeacherCourseByID-==> Parameters: 7003(Integer)
[lsjSso]2021-10-19 22:58:56,556-com.mybatis03.mapper.TeacherCourseMapper.queryTeacherCourseByID-95932[main]DEBUGcom.mybatis03.mapper.TeacherCourseMapper.queryTeacherCourseByID-<==      Total: 1
教师编号：1003,教师名称：peter,教师课程编号:7003
教师对应课程信息：[课程编号=7003,课程名称japanese]
[lsjSso]2021-10-19 22:59:05,300-com.mybatis03.mapper.TeacherCourseMapper.queryTeacherCourseByID-104676[main]DEBUGcom.mybatis03.mapper.TeacherCourseMapper.queryTeacherCourseByID-==>  Preparing: SELECT * FROM teachercourse WHERE courseno = ? 
[lsjSso]2021-10-19 22:59:05,300-com.mybatis03.mapper.TeacherCourseMapper.queryTeacherCourseByID-104676[main]DEBUGcom.mybatis03.mapper.TeacherCourseMapper.queryTeacherCourseByID-==> Parameters: 7004(Integer)
[lsjSso]2021-10-19 22:59:05,301-com.mybatis03.mapper.TeacherCourseMapper.queryTeacherCourseByID-104677[main]DEBUGcom.mybatis03.mapper.TeacherCourseMapper.queryTeacherCourseByID-<==      Total: 1
教师编号：1004,教师名称：jack,教师课程编号:7004
教师对应课程信息：[课程编号=7004,课程名称German]
Disconnected from the target VM, address: '127.0.0.1:31862', transport: 'socket'

Process finished with exit code 0

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Mybatis查询mysql延时加载操作（18）

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Mybatis查询mysql延时加载操作 （18）

前端开发

后端开发

移动端开发

数据库

服务器运维

人工智能

区块链

游戏开发

网站运营

大数据/云计算

软件工程

软件/开发工具使用

资讯

Mybatis查询mysql延时加载操作（18）