Mybatis的一对一和一对多

一对一

介绍

一对一使用的是标签，这个标签有column、javaType和property三个属性，其中column对应的是外键id（使用查询结果的字段），javaType是外键对象的类型，property是外键对象在主对象中的属性名称。这个标签包含两个子标签，分别是其中有

实例

一个老师对象对应一门课程，老师对象有老师工号（teacherId）、老师姓名（teacherName）、和一个课程对象（cursor），课程对象有课程编号（cursorId）、课程名称(cursorName)。

java类

public class Teacher{
    private String teacherId;
    private String teacherName;
    private Cursor cursor;
    public void setTeacherId(String teacherId){
        this.teacherId=teacherId;
    }
    public String getTeacherId(){
        return this.teacherId;
    }
    public void setTeacherName(String teacherName){
        this.teacherName=teacherName;
    }
    public String getTeacherName(){
        return this.teacherName;
    }
     public void setCursor(Cursor cursor){
        this.cursor=cursor;
    }
    public String getCursor(){
        return this.cursor;
    }
}

public class Cursor{
    private String cursorId;
    private String cursorName;
    public void setCursorId(String cursorId){
        this.cursorId=cursorId;
    }
    public String getCursorId(){
        return this.cursorId;
    }
    public void setCursorName(String cursorName){
        this.cursorName=cursorName;
    }
    public String getCursorName(){
        return this.cursorName;
    }
}

xml的配置

id="teacherMap" type="Teacher">
    <id column="teacher_id" jdbcType="VARCHAR" property="teacherId"/>
    <result column="teacher_name" jdbcType="VARCHAR" property="teacherName"/>
    "cursor_id" javaType="Cursor" property="cursor">
        <id column="cursor_id" jdbcType="VARCHAR" property="cursorId"/>
        <result column="cursor_name" jdbcType="VARCHAR" property="cursorName"/>
    

sql语句

select a.teacher_id,a.teacher_name,b.cursor_id,b.cursor_name from teacher a left join cursor b on a.cursor_id=b.id

一对多

介绍

一对多使用的是标签，此标签有column、ofType、property三个属性，column对应的是外键（查询结果的字段）,ofType是外键对象的类型，property是指外键对象在主对象中的名称，这个标签包含两个子标签，分别是其中有

实例

一个老师对应多名学生，老师对象包含有老师工号（teacherId），老师姓名（teacherName)，学生对象集合（Liststudents），学生对象包含有学生学号（student_id），学生姓名（student_name）

java 类

public class Teacher{
    private String teacherId;
    private String teacherName;
    private List students;
    public void setTeacherId(String teacherId){
        this.teacherId=teacherId;
    }
    public String getTeacherId(){
        return this.teacherId;
    }
    public void setTeacherName(String teacherName){
        this.teacherName=teacherName;
    }
    public String getTeacherName(){
        return this.teacherName;
    }
     public void setStudents(List students){
        this.students=students;
    }
    public String getStudents(){
        return this.students;
    }
}

public class Student{
    private String cursorId;
    private String cursorName;
    public void setStudentId(String studentId){
        this.studentId=studentId;
    }
    public String getStudentId(){
        return this.studentId;
    }
    public void setStudentName(String studentName){
        this.studentName=studentName;
    }
    public String getStudentName(){
        return this.studentName;
    }
}

xml配置

id="teacherMap" type="Teacher">
    <id column="teacher_id" jdbcType="VARCHAR" property="teacherId"/>
    <result column="teacher_name" jdbcType="VARCHAR" property="teacherName"/>
    "student_id" ofType="student" property="students">
        <id column="student_id" jdbcType="VARCHAR" property="studentId"/>
        <result column="student_name" jdbcType="VARCHAR" property="studentName">
    

sql

select a.teacher_id,a.teacher_name,b.student_id,b.student_name from teacher a left join student b on a.teacher_id=b.teacher_id

以上内容没有提供具体的数据库数据和创建数据的sql请自行创建。