Mybatis关联查询

实体

package com.smbms.entity;

 

import javax.persistence.*;

import java.util.ArrayList;

import java.util.List;

 

 

public class StudentinfoEntity {

    private int stuid;

    private String studentname;

    private String sex;

    private String address;

    private String birthday;

    //多的一方的教师

    private List<TeacherEntity> teachers=new ArrayList<>();

 

    public int getStuid() {

        return stuid;

    }

 

    public void setStuid(int stuid) {

        this.stuid = stuid;

    }

 

    public String getStudentname() {

        return studentname;

    }

 

    public void setStudentname(String studentname) {

        this.studentname = studentname;

    }

 

    public String getSex() {

        return sex;

    }

 

    public void setSex(String sex) {

        this.sex = sex;

    }

 

    public String getAddress() {

        return address;

    }

 

    public void setAddress(String address) {

        this.address = address;

    }

 

    public String getBirthday() {

        return birthday;

    }

 

    public void setBirthday(String birthday) {

        this.birthday = birthday;

    }

 

    public List<TeacherEntity> getTeachers() {

        return teachers;

    }

 

    public void setTeachers(List<TeacherEntity> teachers) {

        this.teachers = teachers;

    }

}

package com.smbms.entity;

 

import javax.persistence.*;

import java.util.ArrayList;

import java.util.List;

 

 

public class TeacherEntity {

    private int tid;

    private String tname;

    //多的一方的学生实体

    private List<StudentinfoEntity> students=new ArrayList<>();

 

    public int getTid() {

        return tid;

    }

 

    public void setTid(int tid) {

        this.tid = tid;

    }

 

    public String getTname() {

        return tname;

    }

 

    public void setTname(String tname) {

        this.tname = tname;

    }

 

    public List<StudentinfoEntity> getStudents() {

        return students;

    }

 

    public void setStudents(List<StudentinfoEntity> students) {

        this.students = students;

    }

}

接口：

package com.smbms.dao;

 

import com.smbms.entity.TeacherEntity;

 

import java.util.List;

 

//关联查询多对多

public interface TeacherMapper {

 

    //查询所以教师(包括所教学员)

    List<TeacherEntity> getAllTeacher();

}

 

配置：

<?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">

<!-- namespace属性代表该Mapper文件的唯一标识，通常习惯设置mapper接口名-->

<mapper namespace="com.smbms.dao.TeacherMapper">

    <resultMap id="teacherMap" type="TeacherEntity">

        <id column="tid" property="tid"></id>

        <result column="tname" property="tname"></result>

        <!--为students集合设置关联属性-->

        <collection property="students" ofType="StudentinfoEntity">

            <id column="stuid" property="stuid"></id>

            <result column="studentname" property="studentname"></result>

            <result column="sex" property="sex"></result>

            <result column="address" property="address"></result>

            <result column="birthday" property="birthday"></result>

        </collection>

    </resultMap>

 

    <select id="getAllTeacher" resultMap="teacherMap">

        SELECT s.*,t.* FROM teacher t,studentinfo s,teastu ts

        WHERE t.`tid`=ts.`tid` AND s.`stuid`=ts.`stuid`

    </select>

</mapper>

测试：

package com.smbms.test;

 

import com.smbms.dao.TeacherMapper;

import com.smbms.entity.TeacherEntity;

import com.smbms.util.MybatisUtil;

import org.apache.ibatis.session.SqlSession;

import org.junit.After;

import org.junit.Before;

import org.junit.Test;

 

import java.util.List;

 

public class Demo05 {

    SqlSession session=null;

    TeacherMapper mapper=null;

    @Before

    public void before(){

        session= MybatisUtil.getSqlSession();

        mapper=session.getMapper(TeacherMapper.class);

    }

 

    @Test

    public void test01(){

        List<TeacherEntity> teachers = mapper.getAllTeacher();

        //重写Teacher类和Student类中的toString方法 直接打印

        for (TeacherEntity item:teachers){

            System.out.println(item);

        }

    }

 

    @After

    public void after() {

        session.commit();//事务提交

        session.close();//释放se

    }

}

自关联

package com.smbms.entity;   import javax.persistence.*; import java.util.ArrayList; import java.util.List;     public class ProductCategoryEntity {     private int id;     private String name;     private int type;     private List<ProductCategoryEntity> lists=new ArrayList<>();           public int getId() {         return id;     }       public void setId(int id) {         this.id = id;     }       public String getName() {         return name;     }       public void setName(String name) {         this.name = name;     }       public int getType() {         return type;     }       public void setType(int type) {         this.type = type;     }       public List<ProductCategoryEntity> getLists() {         return lists;     }       public void setLists(List<ProductCategoryEntity> lists) {         this.lists = lists;     } }

接口：

package com.smbms.dao;   import com.smbms.entity.ProductCategoryEntity; //自关联 public interface CategoryMapper {     //查询一级分类(包括其下的子分类)     ProductCategoryEntity getOneById(int categoryid); }

测试：

package com.smbms.test;

 

import com.smbms.dao.CategoryMapper;

import com.smbms.entity.ProductCategoryEntity;

import com.smbms.util.MybatisUtil;

import org.apache.ibatis.session.SqlSession;

import org.junit.After;

import org.junit.Before;

import org.junit.Test;

 

public class Demo06 {

    SqlSession session=null;

    CategoryMapper mapper=null;

    @Before

    public void before(){

        session= MybatisUtil.getSqlSession();

        mapper=session.getMapper(CategoryMapper.class);

    }

    @Test

    public void test01(){

       ProductCategoryEntity cate = mapper.getOneById(548);

        //重写Category类中的toString方法 直接打印

        System.out.println(cate);

 

    }

 

    @After

    public void after(){

        session.commit();//事务提交

        session.close();//释放session

    }

}