Mybatis关联查询

一对多：一个用户对应多个角色

实体：

package com.smbms.entity;

import javax.persistence.*;
import java.sql.Timestamp;
import java.util.Date;
import java.util.List;


public class SmbmsRoleEntity {
    private long rid;
    private String roleCode;
    private String roleName;
    private Long createdBy;
    private Timestamp creationDate;
    private Long modifyBy;
    private Timestamp modifyDate;

    //植入多的一方 集合
    private List<SmbmsUserEntity>  userList;

    public long getRid() {
        return rid;
    }

    public void setRid(long rid) {
        this.rid = rid;
    }

    public String getRoleCode() {
        return roleCode;
    }

    public void setRoleCode(String roleCode) {
        this.roleCode = roleCode;
    }

    public String getRoleName() {
        return roleName;
    }

    public void setRoleName(String roleName) {
        this.roleName = roleName;
    }

    public Long getCreatedBy() {
        return createdBy;
    }

    public void setCreatedBy(Long createdBy) {
        this.createdBy = createdBy;
    }

    public Timestamp getCreationDate() {
        return creationDate;
    }

    public void setCreationDate(Timestamp creationDate) {
        this.creationDate = creationDate;
    }

    public Long getModifyBy() {
        return modifyBy;
    }

    public void setModifyBy(Long modifyBy) {
        this.modifyBy = modifyBy;
    }

    public Timestamp getModifyDate() {
        return modifyDate;
    }

    public void setModifyDate(Timestamp modifyDate) {
        this.modifyDate = modifyDate;
    }

    public List<SmbmsUserEntity> getUserList() {
        return userList;
    }

    public void setUserList(List<SmbmsUserEntity> userList) {
        this.userList = userList;
    }
}

　　

接口：

package com.smbms.dao;

import com.smbms.entity.SmbmsRoleEntity;

public interface ISmbmsRoleDao {

    //查询经理角色 以及 该角色下对应的员工集合
    public SmbmsRoleEntity getRoleAndUser(Integer id);

}

　

小配置：

<?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.ISmbmsRoleDao">
    <!--由于是关联查询 返回的是多张表中的结果集，必须定义resultMap映射-->
    <resultMap id="countryMap" type="SmbmsRoleEntity">
        <id property="rid" column="rid"></id>
        <result property="roleName" column="roleName"></result>
        <!--此处使用的是collection节点，由于在Country类中插入的是List集合
            ofType:为集合中的泛型
        -->
        <collection property="userList" ofType="SmbmsUserEntity"  select="gerRoleAndUserMutilSQL" column="rid">
            <!--在collection中声明Provincial中的属性与表中列的映射-->
            <id column="id" property="id"></id>
            <result column="userName" property="userName"></result>
        </collection>
    </resultMap>

   <!-- <select id="getRoleAndUser" parameterType="int" resultMap="countryMap">

        select u.id,u.userName,u.userRole,r.rid,r.roleName from smbms_user as u ,smbms_role as r where u.userRole=r.rid and r.rid=#{id}
    </select>-->

    <select id="getRoleAndUser" resultMap="countryMap">
        select * from smbms_role where rid=#{id}
    </select>

    <select id="gerRoleAndUserMutilSQL"  resultType="SmbmsUserEntity">
        select * from smbms_user where userRole=#{rid}
    </select>
</mapper>

　　

测试：

package com.smbms.test;

import com.smbms.dao.ISmbmsRoleDao;
import com.smbms.entity.SmbmsRoleEntity;
import com.smbms.entity.SmbmsUserEntity;
import com.smbms.util.MybatisUtil;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

public class Demo01 {
    @Test
    public void  getRoleAndUserTest(){
        SqlSession sqlSession=MybatisUtil.getSqlSession();
        ISmbmsRoleDao mapper=sqlSession.getMapper(ISmbmsRoleDao.class);

        SmbmsRoleEntity role=mapper.getRoleAndUser(3);
        System.out.println("角色"+role.getRoleName());
        for (SmbmsUserEntity user:role.getUserList()){
            System.out.println("用户"+user.getUserName());
        }
    }
}

　　

多对一：多个角色对应一个用户

实体：

package com.smbms.entity;

import javax.persistence.*;
import java.sql.Date;
import java.sql.Timestamp;


public class SmbmsUserEntity {
    private long id;
    private String userCode;
    private String userName;
    private String userPassword;
    private Integer gender;
    private Date birthday;
    private String phone;
    private String address;
    private Integer userRole;
    private Long createdBy;
    private Timestamp creationDate;
    private Long modifyBy;
    private Timestamp modifyDate;
    private  SmbmsRoleEntity role;

    public SmbmsRoleEntity getRole() {
        return role;
    }

    public void setRole(SmbmsRoleEntity role) {
        this.role = role;
    }

    public long getId() {
        return id;
    }

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

    public String getUserCode() {
        return userCode;
    }

    public void setUserCode(String userCode) {
        this.userCode = userCode;
    }

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public String getUserPassword() {
        return userPassword;
    }

    public void setUserPassword(String userPassword) {
        this.userPassword = userPassword;
    }

    public Integer getGender() {
        return gender;
    }

    public void setGender(Integer gender) {
        this.gender = gender;
    }

    public Date getBirthday() {
        return birthday;
    }

    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }

    public String getPhone() {
        return phone;
    }

    public void setPhone(String phone) {
        this.phone = phone;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    public Integer getUserRole() {
        return userRole;
    }

    public void setUserRole(Integer userRole) {
        this.userRole = userRole;
    }

    public Long getCreatedBy() {
        return createdBy;
    }

    public void setCreatedBy(Long createdBy) {
        this.createdBy = createdBy;
    }

    public Timestamp getCreationDate() {
        return creationDate;
    }

    public void setCreationDate(Timestamp creationDate) {
        this.creationDate = creationDate;
    }

    public Long getModifyBy() {
        return modifyBy;
    }

    public void setModifyBy(Long modifyBy) {
        this.modifyBy = modifyBy;
    }

    public Timestamp getModifyDate() {
        return modifyDate;
    }

    public void setModifyDate(Timestamp modifyDate) {
        this.modifyDate = modifyDate;
    }
}

　　

接口：

package com.smbms.dao;

import com.smbms.entity.SmbmsUserEntity;

import java.util.List;

public interface ISmbmsUserDao {

    //查询所有用户信息 包含角色信息
    public List<SmbmsUserEntity> getUserList();
}

　　

小配置：

<?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.ISmbmsUserDao">
    <resultMap id="ProvincialMap" type="SmbmsUserEntity">
        <id column="id" property="id"></id>
        <result column="userName" property="userName"></result>
        <!--当关联对象为普通对象时，使用association标签
            javaType:为关联对象的类型
        -->
        <association property="role" javaType="SmbmsRoleEntity">
            <id column="rid" property="rid"></id>
            <result column="roleName" property="roleName"></result>
        </association>
    </resultMap>
    <select id="getUserList" resultMap="ProvincialMap">
         select u.id,u.userName,u.userRole,r.rid,r.roleName from smbms_user as  u,smbms_role as r  where u.userRole=r.rid
    </select>
</mapper>

　　

测试：

package com.smbms.test;

import com.smbms.dao.ISmbmsRoleDao;
import com.smbms.dao.ISmbmsUserDao;
import com.smbms.entity.SmbmsRoleEntity;
import com.smbms.entity.SmbmsUserEntity;
import com.smbms.util.MybatisUtil;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class Demo {
    @Test
    public void  getRoleAndUserTest(){
        SqlSession sqlSession= MybatisUtil.getSqlSession();
        ISmbmsUserDao mapper=sqlSession.getMapper(ISmbmsUserDao.class);

        List<SmbmsUserEntity>  userList=mapper.getUserList();

        for (SmbmsUserEntity user:userList){
            System.out.println("用户"+user.getUserName()+"	角色"+user.getRole().getRoleName() );
        }
    }
}

　　

多对多：多个教师对应多个学生

实体：教师

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;
    }
}

　　

学生：

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();
}

　　

小配置：

<?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：一个分类下存在多个子分类

实体：

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);
}

　　

小配置：

<?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.CategoryMapper">
    <resultMap id="cateMap" type="ProductCategoryEntity">
        <id column="id" property="id"></id>
        <result column="name" property="name"></result>
        <result column="type" property="type"></result>
        <!--
          参照实体类，lists变量的类型是集合(典型的1:N的关系)
          select:指定查询关联对象的select语句(getOneByParent)
          column:查询关联对象select语句的条件值
          本例:根据id获取对应的分类后，以此id为条件获取子级分类(parentId=父级分类ID)
        -->
        <collection property="lists" ofType="ProductCategoryEntity" select="getOneByParent" column="id"/>
    </resultMap>

    <select id="getOneById" parameterType="int" resultMap="cateMap">
        select * from product_category where id=#{cateid}
    </select>

    <select id="getOneByParent" parameterType="int" resultMap="cateMap">
        select * from product_category where parentId=#{id}
    </select>
</mapper>

　　

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
    }
}