Mybatis一对多及多对多映射查询

1、数据库准备工作

--删除表
drop table SelectiveInfo;
drop table StudentInfo;
drop table ClassInfo;
drop table TeacherInfo;
drop table CourseInfo;
drop table DepartmentInfo;--创建部门表
create table DepartmentInfo(departmentCode varchar2(5),departmentName varchar2(64) unique,constraint PK_DepartmentInfo primary key(departmentCode));
--创建课程信息表
create table CourseInfo(courseID varchar2(8),courseName varchar2(32) not null,departmentCode varchar2(5) not null,credit number(3,1) not null,resume varchar2(255),constraint PK_CourseInfo primary key(courseID),constraint FK_Cdepartment foreign key(departmentCode)references DepartmentInfo(departmentCode));
--创建教师信息表
create table TeacherInfo(teacherID varchar2(18),teacherName varchar2(32) not null,departmentCode varchar2(5) not null,sex char(1) not null,tel varchar2(20),fax varchar2(20),teacherBiref varchar2(512),constraint PK_TeacherInfo primary key(teacherID),constraint FK_departmentCode foreign key(departmentCode)references DepartmentInfo(departmentCode));
--创建排课信息表
create table ClassInfo(classID number(10),className varchar2(32) not null,teacherID varchar2(18) not null,courseID varchar2(8) not null,classYear varchar2(6) not null,classTimePlace varchar2(128),constraint PK_ClassInfo primary key(classID),constraint FK_courseID foreign key(courseID)references CourseInfo(courseID),constraint FK_teacherID foreign key(teacherID)references TeacherInfo(teacherID));
--创建学生信息表
create table StudentInfo(studentID varchar2(18),studentName varchar2(32) not null,sex char(1) not null,departmentCode varchar2(5) not null,address varchar2(512),tel varchar2(20),fax varchar2(20),constraint PK_StudentInfo primary key(studentID),constraint FK_department foreign key(departmentCode)references DepartmentInfo(departmentCode));
--创建选课信息表
create table SelectiveInfo(studentID varchar2(18) not null,classID number(10) not null,grade number(4,1),selectiveDate date,status char(1) default 'n',constraint PK_SelectiveInfo primary key(studentID,classID),constraint FK_classID foreign key(classID)references ClassInfo(classID));--添加部门代码信息记录
insert into DepartmentInfo values('101','计算机学院');
insert into DepartmentInfo values('201','软件学院');
insert into DepartmentInfo values('301','工商管理学院');
insert into DepartmentInfo values('401','人文学院');--添加课程信息记录
insert into CourseInfo values('1010001','database manage','201',3.5,'以oralce数据库为例，着重数据库管理基础');
insert into CourseInfo values('1010002','database development','201',2.5,'以oralce数据库为例，着重数据库开发基础');
insert into CourseInfo values('2010001','C++ development','101',3.5,'讲授面向对象编程');
insert into CourseInfo values('2010002','JSP Application','101',1.5,'是Dcampus-0220的后续课程');
insert into CourseInfo values('2010003','Dcampus Enterprise JavaBean','101',2.5,'讲授EJB原理');--添加教师信息
insert into TeacherInfo values('199910110002','angelo smith','101','m','020-87119321','020-87113912','he is a good man');
insert into TeacherInfo values('200210110002','angel rose','101','f','020-87113433','020-87134952','she is a good woman');
insert into TeacherInfo values('200110330002','mark stone','201','m','020-87119321','020-87113912','he is a angel husband');
insert into TeacherInfo values('199910123002','angelo stone','101','s','020-87145521','020-87134912','he is a bad man');
insert into TeacherInfo values('200310123044','wu da wei','301','f','020-87134421','020-87154412','he is a bad man');
insert into TeacherInfo values('200234234099','wang fei','401','f','020-87123231','020-87134412','he is a bad man');--添加排课信息表
insert into ClassInfo values(1,'oracle DBA','199910110002','1010001','2002下','monday 27101,tuesday 12204');
insert into ClassInfo values(2,'oracle Advance DBA','199910110002','1010001','2002下','friday 27101,sunday 12204');
insert into ClassInfo values(3,'C++ fundament Application','200110330002','2010001','2002上','friday 27121,tuesday 13404');
insert into ClassInfo values(4,'C++ Advance Application','199910123002','2010001','2003下','monday 27101,satuday 2704');--添加学生信息
insert into StudentInfo values('2002100230221','liu doudou','m','101','he is a good student','020-45449321','020-45113912');
insert into StudentInfo values('2002100230765','wu wei dong','f','101','she is a good student','020-45443441','020-45176562');
insert into StudentInfo values('2002100345876','he meihua','f','101','she is a good girl','021-45434321','022-45113912');
insert into StudentInfo values('2002100785446','he zhuanzhuan','m','201','this is a joke','023-45433333','025-45143342');
insert into StudentInfo values('2002100343336','tian dehua','m','201','this is a big joke','023-4543334','024-43553342');
insert into StudentInfo values('2002343333336','zhang lili','s','201','this is a smill joke','053-4673334','052-43666342');
insert into StudentInfo values('2002342343445','zhang guorong','m','301','this is a smill joke','053-46343334','052-42326342');
insert into StudentInfo values('2002323423434','mei yanfang','f','401','this is a smill joke','053-46324334','052-42877742');--添加选课信息
insert into SelectiveInfo values('2002343333336',1,67,to_date('2010-12-2','yyyy-mm-dd'),'n');
insert into SelectiveInfo values('2002343333336',2,87,to_date('2010-12-2','yyyy-mm-dd'),'n');
insert into SelectiveInfo values('2002100230765',1,98,to_date('2010-12-3','yyyy-mm-dd'),'n');
insert into SelectiveInfo values('2002100230765',3,88,to_date('2010-12-4','yyyy-mm-dd'),'n');
insert into SelectiveInfo values('2002100345876',1,83,to_date('2010-12-1','yyyy-mm-dd'),'n');
insert into SelectiveInfo values('2002100345876',4,71,to_date('2010-12-3','yyyy-mm-dd'),'n');
insert into SelectiveInfo values('2002100785446',3,85,to_date('2010-11-30','yyyy-mm-dd'),'n');
insert into SelectiveInfo values('2002100785446',2,74,to_date('2010-11-28','yyyy-mm-dd'),'n');
insert into SelectiveInfo values('2002100230221',1,61,to_date('2010-12-3','yyyy-mm-dd'),'n');
insert into SelectiveInfo values('2002100230221',2,58,to_date('2010-12-4','yyyy-mm-dd'),'n');
insert into SelectiveInfo values('2002100230221',3,69,to_date('2010-12-5','yyyy-mm-dd'),'n');
insert into SelectiveInfo values('2002100343336',2,55,to_date('2010-12-2,15:30:44','yyyy-mm-dd,hh24:mi:ss'),'n');
insert into SelectiveInfo values('2002100343336',4,66,sysdate,'n');

2、编写JavaBean(可跳过此步查阅第三步)

DepartmentInfoVo.java

import java.util.ArrayList;import com.luo.ssm.po.StudentInfo;public class DepartmentInfoVo {private String DEPARTMENTCODE;private String DEPARTMENTNAME;private ArrayList<StudentInfo> stuList;public ArrayList<StudentInfo> getStuList() {return stuList;}public void setStuList(ArrayList<StudentInfo> stuList) {this.stuList = stuList;}public String getDEPARTMENTCODE() {return DEPARTMENTCODE;}public void setDEPARTMENTCODE(String dEPARTMENTCODE) {DEPARTMENTCODE = dEPARTMENTCODE;}public String getDEPARTMENTNAME() {return DEPARTMENTNAME;}public void setDEPARTMENTNAME(String dEPARTMENTNAME) {DEPARTMENTNAME = dEPARTMENTNAME;}@Overridepublic String toString() {return "DepartmentInfoVo [DEPARTMENTCODE=" + DEPARTMENTCODE + ", DEPARTMENTNAME=" + DEPARTMENTNAME+ ", stuList=" + stuList + "]";}}

StudentInfo.java

public class StudentInfo {private String STUDENTID;private String STUDENTNAME;private char SEX;private String DEPARTMENTCODE;private String ADDRESS;private String TEL;private String FAX;private SelectiveInfo selectiveInfo;public String getSTUDENTID() {return STUDENTID;}public void setSTUDENTID(String sTUDENTID) {STUDENTID = sTUDENTID;}public String getSTUDENTNAME() {return STUDENTNAME;}public void setSTUDENTNAME(String sTUDENTNAME) {STUDENTNAME = sTUDENTNAME;}public char getSEX() {return SEX;}public void setSEX(char sEX) {SEX = sEX;}public String getDEPARTMENTCODE() {return DEPARTMENTCODE;}public void setDEPARTMENTCODE(String dEPARTMENTCODE) {DEPARTMENTCODE = dEPARTMENTCODE;}public String getADDRESS() {return ADDRESS;}public void setADDRESS(String aDDRESS) {ADDRESS = aDDRESS;}public String getTEL() {return TEL;}public void setTEL(String tEL) {TEL = tEL;}public String getFAX() {return FAX;}public void setFAX(String fAX) {FAX = fAX;}@Overridepublic String toString() {return "StudentInfo [STUDENTID=" + STUDENTID + ", STUDENTNAME=" + STUDENTNAME + ", SEX=" + SEX+ ", DEPARTMENTCODE=" + DEPARTMENTCODE + ", ADDRESS=" + ADDRESS + ", TEL=" + TEL + ", FAX=" + FAX+ ", selectiveInfo=" + selectiveInfo + "]";}}

SelectiveInfo.java

public class SelectiveInfo {private String STUDENTID;private String CLASSID;private String GRADE;private String SELECTIVEDATE;private String STATUS;private Classinfo classinfo;public String getSTUDENTID() {return STUDENTID;}public void setSTUDENTID(String sTUDENTID) {STUDENTID = sTUDENTID;}public String getCLASSID() {return CLASSID;}public void setCLASSID(String cLASSID) {CLASSID = cLASSID;}public String getGRADE() {return GRADE;}public void setGRADE(String gRADE) {GRADE = gRADE;}public String getSELECTIVEDATE() {return SELECTIVEDATE;}public void setSELECTIVEDATE(String sELECTIVEDATE) {SELECTIVEDATE = sELECTIVEDATE;}public String getSTATUS() {return STATUS;}public void setSTATUS(String sTATUS) {STATUS = sTATUS;}public Classinfo getClassinfo() {return classinfo;}public void setClassinfo(Classinfo classinfo) {this.classinfo = classinfo;}@Overridepublic String toString() {return "SelectiveInfo [STUDENTID=" + STUDENTID + ", CLASSID=" + CLASSID + ", GRADE=" + GRADE+ ", SELECTIVEDATE=" + SELECTIVEDATE + ", STATUS=" + STATUS + ", classinfo=" + classinfo + "]";}}

ClassInfo.java

public class ClassInfo {private String CLASSID;private String CLASSNAME;private String TEACHERID;private String COURSEID;private String CLASSYEAR;private String CLASSTIMEPLACE;public String getCLASSID() {return CLASSID;}public void setCLASSID(String cLASSID) {CLASSID = cLASSID;}public String getCLASSNAME() {return CLASSNAME;}public void setCLASSNAME(String cLASSNAME) {CLASSNAME = cLASSNAME;}public String getTEACHERID() {return TEACHERID;}public void setTEACHERID(String tEACHERID) {TEACHERID = tEACHERID;}public String getCOURSEID() {return COURSEID;}public void setCOURSEID(String cOURSEID) {COURSEID = cOURSEID;}public String getCLASSYEAR() {return CLASSYEAR;}public void setCLASSYEAR(String cLASSYEAR) {CLASSYEAR = cLASSYEAR;}public String getCLASSTIMEPLACE() {return CLASSTIMEPLACE;}public void setCLASSTIMEPLACE(String cLASSTIMEPLACE) {CLASSTIMEPLACE = cLASSTIMEPLACE;}@Overridepublic String toString() {return "Classinfo [CLASSID=" + CLASSID + ", CLASSNAME=" + CLASSNAME + ", TEACHERID=" + TEACHERID + ", COURSEID="+ COURSEID + ", CLASSYEAR=" + CLASSYEAR + ", CLASSTIMEPLACE=" + CLASSTIMEPLACE + "]";}}

3、编写StuMapper.java接口方法

public interface StuMapper {//一对多查询public List<DepartmentInfoVo> departmentInfoVoList(String DEPARTMENTCODE);//多对多查询public List<Object> selectNtoN(String DEPARTMENTCODE);}

4、编写StuMapper.xml映射文件

注意映射文件<mapper>标签的namespace属性须填写同名接口的全类名。
1.collection用于一对多的关系，而association是用于一对一和多对一，对此有疑问者可查阅详解Mybatis中collection和association的使用区别。
2.javaType和ofType都可以用来指定对象类型，但javaType用来指定pojo中属性的类型，而ofType则用来指定映射到list集合中pojo的属性类型。
3.一对多关系：一个部门对应着对多个学生。
4.多对多关系：一个部门对应着多个学生，一个学生对应着多个选课，一个选课对应着一个课程排课。

<?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"><mapper namespace="com.luo.ssm.dao.StuMapper"><!-- 一对多查询(1) --><resultMap type="com.luo.ssm.po.DepartmentInfoVo" id="departmentInfoVoMapper"><id column="DEPARTMENTCODE" property="DEPARTMENTCODE"/><result column="DEPARTMENTNAME" property="DEPARTMENTNAME"/><collection property="stuList" ofType="com.luo.ssm.po.StudentInfo"><id column="STUDENTID" property="STUDENTID"/><result column="STUDENTNAME" property="STUDENTNAME"/><result column="SEX" property="SEX"/><result column="DEPARTMENTCODE" property="DEPARTMENTCODE"/><result column="ADDRESS" property="ADDRESS"/><result column="TEL" property="TEL"/><result column="FAX" property="FAX"/></collection></resultMap><!-- 一对多查询(2) collection:一对多 association：多对一，一对一--><select id="departmentInfoVoList" parameterType="String" resultMap="departmentInfoVoMapper" >SELECT s.STUDENTID,s.STUDENTNAME,d.DEPARTMENTCODE,d.DEPARTMENTNAME FROM STUDENTINFO s,DEPARTMENTINFO d where s.DEPARTMENTCODE=#{DEPARTMENTCODE} and d.DEPARTMENTCODE=#{DEPARTMENTCODE} </select><!-- 多对多查询(1) --><resultMap type="com.luo.ssm.po.DepartmentInfoVo" id="selectNtoNresultMap"><result column="DEPARTMENTCODE" property="DEPARTMENTCODE"/><result column="DEPARTMENTNAME" property="DEPARTMENTNAME"/><collection property="stuList" ofType="com.luo.ssm.po.StudentInfo"><result column="STUDENTID" property="STUDENTID"/><result column="STUDENTNAME" property="STUDENTNAME"/><collection property="selectiveInfo" ofType="com.luo.ssm.po.SelectiveInfo" ><result column="CLASSID" property="CLASSID"/><result column="GRADE" property="GRADE"/><result column="SELECTIVEDATE" property="SELECTIVEDATE"/><association property="classinfo" javaType="com.luo.ssm.po.ClassInfo"><result column="CLASSNAME" property="CLASSNAME"/><result column="CLASSID" property="CLASSID"/><result column="CLASSTIMEPLACE" property="CLASSTIMEPLACE"/></association></collection></collection></resultMap><!-- 多对多查询(2) --><select id="selectNtoN" resultMap="selectNtoNresultMap">SELECT d.DEPARTMENTCODE,d.DEPARTMENTNAME,stu.STUDENTID,stu.STUDENTNAME,sel.CLASSID,sel.GRADE,sel.SELECTIVEDATE,c.CLASSID,c.CLASSNAME,c.CLASSTIMEPLACE FROM DEPARTMENTINFO d,STUDENTINFO stu,SELECTIVEINFO sel,CLASSINFO c where d.DEPARTMENTCODE=#{DEPARTMENTCODE}AND stu.DEPARTMENTCODE=#{DEPARTMENTCODE} AND stu.STUDENTID=sel.STUDENTID AND sel.CLASSID=c.CLASSID<!-- 末尾添加分号会报错 --></select>
</mapper>

5、编写测试类
SelectTest.java

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Map;import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.context.support.ClassPathXmlApplicationContext;import com.luo.ssm.dao.StuMapper;
import com.luo.ssm.po.DepartmentInfoVo;public class SelectTest {public static void main(String[] args) {try {BeanFactory beanFactory = new ClassPathXmlApplicationContext("spring/applicationContext.xml");SqlSessionFactory sqlSessionFactory=(SqlSessionFactory) beanFactory.getBean("sqlSessionFactory");SqlSession session=sqlSessionFactory.openSession();/*    //一对多查询String DEPARTMENTCODE="101";List<DepartmentInfoVo> list=session.selectList("departmentInfoVoList",DEPARTMENTCODE);for (Object object : list) {System.out.println(object.toString());}    *///多对多查询String DEPARTMENTCODE="101";List<Object> list=session.selectList("selectNtoN",DEPARTMENTCODE);for (Object object : list) {System.out.println(object.toString());}} catch (Exception e) {e.printStackTrace();}}}

5、执行测试类

数据库查询结果
注意：测试类打印输出时，只输出对应的STUDENTID信息的最后一个，即每个STUDENTID仅输出一次，如需输出以下数据库结果需做特殊处理，需将 StudentInfo.java 中 private SelectiveInfo selectiveInfo 及 SelectiveInfo.java 中 private Classinfo classinfo 映射到list集合中pojo的属性类型，如：DepartmentInfoVo 中的 private ArrayList<StudentInfo> stuList。

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