使用resultMap實現高級結果映射

本文轉載自查看原文 2019-10-12 15:25 430

使用resultMap實現高級結果映射

resultMap的屬性:

1.屬性

id：resultMap的唯一標識。
type：resulMap的映射結果類型（一般為Java實體類）。
2.子節點

id：一般對應數據庫的主鍵 id，設置此項可以提升數據庫性能。
result：映射到JavaBean的某個 “ 簡單類型 ” 屬性，如基礎數據類型，包裝類等。子節點 id 和 result 均可以實現最基本的結果集映射，將列映射到簡單數據類型的屬性。。這兩者唯一不同的是：在比較對象實例時 id 將作為結果集的標識屬性。這有助於提高總體性能，特別是應用緩存的嵌套結果映射的時候，若需要實現高級結果映射，就需要下面兩個配置項：association 和 collection
association（僅處理一對一的關聯關系）

<resultMap type="User" id="userRoleResult">
　　<id property="id" column="id"/>
　　<result property="userName" column="userName"/>
　　<association property="role" javaType="Role">
　　　　<id property="roleName" column="roleName"/>
　　</association>
</resultMap>

javaType：完整Java類名或者別名。若映射到一個JavaBean，則MyBatis通常會自行檢測到其類型；若映射到一個HashMap，則應該明確指定javaType，類確保所需行為。此處為Role。
property：映射到數據庫列的實體對象的屬性，此處為在User實體類里定義的JavaBean對象屬性（role）。association的子元素如下：
id。
result。
property：映射到數據庫列的實體類對象的屬性。此處為Role的屬性。
column：數據庫列名或者別名。
在做結果映射的過程中，要確保所有的列名都是唯一無歧義的。

collection（屬性是一個集合列表）

<resultMap type="User" id="userRoleResult">
　　<id property="id" column="id"/>
　　<result property="userName" column="userName"/>
　　<collection property="List" ofType="Address">
　　　　<id property="id" column="id"/>
　　　　<result property="postCode" column="postCode"/>
　　</collection>
</resultMap>

ofType：完整Java類名或者別名，即集合所包含的類型，此處為Address。
property：映射數據庫列的實體類對象的屬性。此處為在User里定義的屬性：List（可以理解為一個名為List，元素類型為Address的ArrayList集合）
collection的子元素與association基本一致。

一對多

實體

package com.smbms.entity; import java.math.BigInteger; import java.util.Date; import java.util.List; /** * 角色 */


public class SmbmsRole {　　　　　　　　　　　　　　
    private Integer rid;
    private String roleCode;
    private String roleName;
    private BigInteger createdBy;
    private Date creationDate;
    private BigInteger modifyBy;
    private Date modifyDate;

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

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

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

    public Integer getRid() {
        return rid;
    }

    public void setRid(Integer 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 BigInteger getCreatedBy() {
        return createdBy;
    }

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

    public Date getCreationDate() {
        return creationDate;
    }

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

    public BigInteger getModifyBy() {
        return modifyBy;
    }

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

    public Date getModifyDate() {
        return modifyDate;
    }

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

　DAO層


package com.smbms.dao;

import com.smbms.entity.SmbmsUser;

import java.util.List;

public interface ISmbmsUserDao {
    //查詢所有用戶信息  包含角色信息
    public List<SmbmsUser> getUserList();
}

　DAO層XML

<?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需要指向接口全路徑-->
<mapper namespace="com.smbms.dao.ISmbmsRoleDao">
    <resultMap id="roleAndUserMapper" type="SmbmsRole">
        <id column="rid" property="rid"></id>
        <result column="roleName" property="roleName"/>
        <!--映射多的一方 property代表實體當中多的一方的屬性名      ofType代表集合當中泛型類型-->
        <!-- select 代表執行查詢的ID   column所引用的條件列   -->
        <collection property="userList" ofType="SmbmsUser" select="getRoleAndUserMutilSQL" column="rid">

        </collection>
    </resultMap>
    
    <!--寫成一條sql-->
    <select id="getRoleAndUser" resultMap="roleAndUserMapper">
        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>
    <!--寫成兩條sql-->
    <select id="getRoleAndUser" resultMap="roleAndUserMapper">
        select * from  smbms_role where rid=#{id}
    </select>
    <select id="getRoleAndUserMutilSQL" resultType="SmbmsUser">
        select * from  smbms_user where userRole=#{rid}
    </select>
</mapper>

測試

package com.smbms.test;

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

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


        SmbmsRole role = mapper.getRoleAndUser(3);
        System.out.println("角色："+role.getRoleName());
        for(SmbmsUser user : role.getUserList()){
            System.out.print("\t用戶："+user.getUserName());
        }
    }
}

多對一　

實體

package com.smbms.entity;


import java.math.BigInteger;
import java.util.Date;

/**
 *
 */
public class SmbmsUser {
    private Integer 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 BigInteger createdBy;
    private Date creationDate;
    private BigInteger modifyBy;
    private Date modifyDate;

    //關聯一的一方
    private SmbmsRole role;

    public SmbmsRole getRole() {
        return role;
    }

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

    public Integer getId() {
        return id;
    }

    public void setId(Integer 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 BigInteger getCreatedBy() {
        return createdBy;
    }

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

    public Date getCreationDate() {
        return creationDate;
    }

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

    public BigInteger getModifyBy() {
        return modifyBy;
    }

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

    public Date getModifyDate() {
        return modifyDate;
    }

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

DAO層

package com.smbms.dao;

import com.smbms.entity.SmbmsUser;

import java.util.List;

public interface ISmbmsUserDao {
    //查詢所有用戶信息  包含角色信息
    public List<SmbmsUser> getUserList();
}

DAO層XML

<?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需要指向接口全路徑-->
<mapper namespace="com.smbms.dao.ISmbmsUserDao">
    <resultMap id="userListAndRole" type="SmbmsUser">
        <id column="id" property="id"></id>
        <result column="userName" property="userName"/>
        <association property="role" javaType="SmbmsRole" select="getRole" column="userRole">
            <id column="rid" property="rid"></id>
            <result column="roleName" property="roleName"/>
        </association>
    </resultMap>

    <!--<select id="getUserList" resultMap="userListAndRole">
        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>-->


    <select id="getUserList" resultMap="userListAndRole">
        select * from smbms_user
    </select>
    <select id="getRole" resultType="SmbmsRole">
        select * from smbms_role where rid=#{userRole}
    </select>
</mapper>

測試

package com.smbms.test;

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

import java.util.List;

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


        List<SmbmsUser> userList = mapper.getUserList();
        for(SmbmsUser user:userList){
            System.out.println("用戶："+user.getUserName()+"\t角色："+user.getRole().getRoleName());
        }
    }
}

多對多

實體

package com.smbms.entity;

import java.util.List;

public class Teacher {
    private Integer tid;
    private String tname;

    //植入學員集合，代表一名教員可以教授多名學員
    private List<Student> students;

    public Integer getTid() {
        return tid;
    }

    public void setTid(Integer tid) {
        this.tid = tid;
    }

    public String getTname() {
        return tname;
    }

    public void setTname(String tname) {
        this.tname = tname;
    }

    public List<Student> getStudents() {
        return students;
    }

    public void setStudents(List<Student> students) {
        this.students = students;
    }
}




package com.smbms.entity;

import java.util.List;

public class Student {
    private Integer stuid;
    private String stuname;
    private String stuaddress;

    //植入Teacher集合，代表一名學員可以被多名教員教授
    private List<Teacher> teachers;

    public List<Teacher> getTeachers() {
        return teachers;
    }

    public void setTeachers(List<Teacher> teachers) {
        this.teachers = teachers;
    }

    public Integer getStuid() {
        return stuid;
    }

    public void setStuid(Integer stuid) {
        this.stuid = stuid;
    }

    public String getStuname() {
        return stuname;
    }

    public void setStuname(String stuname) {
        this.stuname = stuname;
    }

    public String getStuaddress() {
        return stuaddress;
    }

    public void setStuaddress(String stuaddress) {
        this.stuaddress = stuaddress;
    }
}

DAO層

package com.smbms.dao;

import com.smbms.entity.Student;

import java.util.List;

public interface IStudentDao {
    //查詢所有學生信息  以及授課教員
    public List<Student> getStudentInfo();
}

DAO層XML

<?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需要指向接口全路徑-->
<mapper namespace="com.smbms.dao.IStudentDao">
    <resultMap id="studentAndTeacherMapper" type="Student">
        <id column="stuid" property="stuid"/>
        <result column="stuname" property="stuname"/>
        <collection property="teachers" ofType="Teacher">
            <id column="tid" property="tid"></id>
            <result property="tname" column="tname"/>
        </collection>
    </resultMap>
    <select id="getStudentInfo" resultMap="studentAndTeacherMapper">
        select * from student,teacher,stu_t where student.stuid=stu_t.stuid and teacher.tid=stu_t.tid
    </select>
</mapper>

測試

package com.smbms.test;

import com.smbms.dao.IStudentDao;
import com.smbms.entity.Student;
import com.smbms.entity.Teacher;
import com.smbms.util.MybatisUtil;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class ManeyTooManey {
    @Test
    public void getStudentInfo(){
        SqlSession sqlSession = MybatisUtil.getSqlSession();
        IStudentDao mapper = sqlSession.getMapper(IStudentDao.class);

        List<Student> studentInfo = mapper.getStudentInfo();
        for(Student stu:studentInfo){
            System.out.println("學生："+stu.getStuname());
            for (Teacher teacher:stu.getTeachers()){
                System.out.print("\t教員："+teacher.getTname());
            }
            System.out.println();
        }

    }
}

自聯接

實體

package com.smbms.entity;

import java.util.List;

public class City {
    private Integer cid;
    private String cname;
    private Integer pid;
    //自關聯集合     代表的是當前City對象的子集集合
    public List<City> childCitys;

    @Override
    public String toString() {
        return "City{" +
                "cid=" + cid +
                ", cname='" + cname + '\'' +
                ", pid=" + pid +
                ", childCitys=" + childCitys +
                '}';
    }

    public List<City> getChildCitys() {
        return childCitys;
    }

    public void setChildCitys(List<City> childCitys) {
        this.childCitys = childCitys;
    }

    public Integer getCid() {
        return cid;
    }

    public void setCid(Integer cid) {
        this.cid = cid;
    }

    public String getCname() {
        return cname;
    }

    public void setCname(String cname) {
        this.cname = cname;
    }

    public Integer getPid() {
        return pid;
    }

    public void setPid(Integer pid) {
        this.pid = pid;
    }


}

DAO層

package com.smbms.dao;

import com.smbms.entity.City;

import java.util.List;

public interface ICityDao {
    //查詢河南省  下的所有子集
    public City getCityAndChildCitys(Integer cid);
}

DAO層XML

<?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需要指向接口全路徑-->
<mapper namespace="com.smbms.dao.ICityDao">
    <resultMap id="CityAndChildCitysMapper" type="City">
        <id column="cid" property="cid"></id>
        <result column="cname" property="cname"/>
        <result column="pid" property="pid"/>
        <collection property="childCitys" ofType="City" select="getCityAndChildCitysMutilSQL" column="cid">
            <id column="cid" property="cid"></id>
            <result column="cname" property="cname"/>
            <result column="pid" property="pid"/>
        </collection>
    </resultMap>

   <select id="getCityAndChildCitys" resultMap="CityAndChildCitysMapper">
       select * from city where cid=#{cid}
   </select>
    <select id="getCityAndChildCitysMutilSQL" resultMap="CityAndChildCitysMapper">
       select * from city where pid=#{cid}
   </select>
</mapper>

測試

package com.smbms.test;

import com.smbms.dao.ICityDao;
import com.smbms.entity.City;
import com.smbms.util.MybatisUtil;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

public class DGTest {
    @Test
    public void getCityAndChildCitysTest(){
        SqlSession sqlSession = MybatisUtil.getSqlSession();
        ICityDao mapper = sqlSession.getMapper(ICityDao.class);

        City city = mapper.getCityAndChildCitys(410000);
        System.out.println(city.toString());
    }
}

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