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  • oracle使用resultMap实现高级结果映射

    resultMap的属性:

    1.属性

    id：resultMap的唯一标识。
    type：resulMap的映射结果类型（一般为Java实体类）。
    2.子节点

    id：一般对应数据库的主键 id，设置此项可以提升数据库性能。
    result：映射到JavaBean的某个 “ 简单类型 ” 属性，如基础数据类型，包装类等。子节点 id 和 result 均可以实现最基本的结果集映射，将列映射到简单数据类型的属性。。这两者唯一不同的是：在比较对象实例时 id 将作为结果集的标识属性。这有助于提高总体性能，特别是应用缓存的嵌套结果映射的时候，若需要实现高级结果映射，就需要下面两个配置项：association 和 collection
    association（仅处理一对一的关联关系）

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    <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类名或者别名。若映射到一个JavaBean，则MyBatis通常会自行检测到其类型；若映射到一个HashMap，则应该明确指定javaType，类确保所需行为。此处为Role。
    property：映射到数据库列的实体对象的属性，此处为在User实体类里定义的JavaBean对象属性（role）。association的子元素如下：
    id。
    result。
    property：映射到数据库列的实体类对象的属性。此处为Role的属性。
    column：数据库列名或者别名。
    在做结果映射的过程中，要确保所有的列名都是唯一无歧义的。

    collection（属性是一个集合列表）

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    <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类名或者别名，即集合所包含的类型，此处为Address。
    property：映射数据库列的实体类对象的属性。此处为在User里定义的属性：List（可以理解为一个名为List，元素类型为Address的ArrayList集合）
    collection的子元素与association基本一致。

    一对多

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    <span style="color: #ff0000;"><strong><span style="font-size: 18pt;">实体</span></strong></span>
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    package com.smbms.entity; import java.math.BigInteger; import java.util.Date; import java.util.List; /** * 角色 */<br><br>
    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层

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    <br>package com.smbms.dao;
     
    import com.smbms.entity.SmbmsUser;
     
    import java.util.List;
     
    public interface ISmbmsUserDao {
        //查询所有用户信息  包含角色信息
        public List<SmbmsUser> getUserList();
    }

    　DAO层XML

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    <?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需要指向接口全路径-->
    <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代表实体当中多的一方的属性名      ofType代表集合当中泛型类型-->
            <!-- select 代表执行查询的ID   column所引用的条件列   -->
            <collection property="userList" ofType="SmbmsUser" select="getRoleAndUserMutilSQL" column="rid">
     
            </collection>
        </resultMap>
         
        <!--写成一条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>
        <!--写成两条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>

    测试

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    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(" 用户："+user.getUserName());
            }
        }
    }

    多对一　

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    <span style="color: #ff0000;"><strong><span style="font-size: 18pt;">实体</span></strong></span>
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    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;
     
        //关联一的一方
        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;
        }
    }<br><br><br><br><br><br><br>

    　　

    DAO层

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    package com.smbms.dao;
     
    import com.smbms.entity.SmbmsUser;
     
    import java.util.List;
     
    public interface ISmbmsUserDao {
        //查询所有用户信息  包含角色信息
        public List<SmbmsUser> getUserList();
    }

    　　

    DAO层XML

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    <?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需要指向接口全路径-->
    <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>

    　　

    测试

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    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("用户："+user.getUserName()+" 角色："+user.getRole().getRoleName());
            }
        }
    }

    　　

    多对多

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    <span style="color: #ff0000;"><strong><span style="font-size: 18pt;">实体</span></strong></span>
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    package com.smbms.entity;
     
    import java.util.List;
     
    public class Teacher {
        private Integer tid;
        private String tname;
     
        //植入学员集合，代表一名教员可以教授多名学员
        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，代表一名学员可以被多名教员教授
        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层

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    package com.smbms.dao;
     
    import com.smbms.entity.Student;
     
    import java.util.List;
     
    public interface IStudentDao {
        //查询所有学生信息  以及授课教员
        public List<Student> getStudentInfo();
    }

    　　

    DAO层XML

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    <?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需要指向接口全路径-->
    <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>

    　　

    测试

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    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("学生："+stu.getStuname());
                for (Teacher teacher:stu.getTeachers()){
                    System.out.print(" 教员："+teacher.getTname());
                }
                System.out.println();
            }
     
        }
    }

    　　

    自联接

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    <span style="color: #ff0000;"><strong><span style="font-size: 18pt;">实体</span></strong></span>
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    package com.smbms.entity;
     
    import java.util.List;
     
    public class City {
        private Integer cid;
        private String cname;
        private Integer pid;
        //自关联集合     代表的是当前City对象的子集集合
        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层

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    package com.smbms.dao;
     
    import com.smbms.entity.City;
     
    import java.util.List;
     
    public interface ICityDao {
        //查询河南省  下的所有子集
        public City getCityAndChildCitys(Integer cid);
    }

    　　

    DAO层XML

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    <?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需要指向接口全路径-->
    <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>

    　　

    测试

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    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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  • 原文地址：https://www.cnblogs.com/niudaxianren/p/11737093.html
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