mybatis多表开发
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mybatis多表开发
mybatis一对一映射【学生与身份证】
创建students.sql和cards.sql
drop table students;
drop table cards;
create table cards(
id int(5) primary key,
num varchar(20)
);
create table students(
id int(5) primary key,
name varchar(10),
cid int(5),
constraint cid_fk foreign key(cid) references cards(id)
);
insert into cards(id,num) values(1,'111');
insert into students(id,name,cid) values(1,'哈哈',1);创建Students.java和Card.java
public class Card
private Integer id;
private String num;
private Student student;
public Card()
public Integer getId()
return id;
public void setId(Integer id)
this.id = id;
public String getNum()
return num;
public void setNum(String num)
this.num = num;
public Student getStudent()
return student;
public void setStudent(Student student)
this.student = student;
public class Student
private Integer id;
private String name;
private Card card;
public Student()
public Integer getId()
return id;
public void setId(Integer id)
this.id = id;
public String getName()
return name;
public void setName(String name)
this.name = name;
public Card getCard()
return card;
public void setCard(Card card)
this.card = card;
创建StudentMapper.xml和CardMapper.xml
<!--CardMapper.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">
<mapper namespace="cardNamespace">
<resultMap type="cn.csx.javaee.mybatis.one2one.Card" id="cardMap">
<id property="id" column="id" />
<result property="num" column="num" />
</resultMap>
</mapper>
<!--StudentMapper.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">
<mapper namespace="studentNamespace">
<resultMap type="cn.csx.javaee.mybatis.one2one.Student" id="studentMap">
<id property="id" column="id" />
<result property="name" column="name"/>
<association property="card" resultMap="cardNamespace.cardMap"/>
</resultMap>
<select id="findById" parameterType="int" resultMap="studentMap">
select s.id,s.name,c.id,c.num
from students s inner join cards c
on s.cid = c.id
and s.id = #id
</select>
</mapper>创建StudentCardDao.java
public class StudentCardDao
/**
* 查询1号【学生】
*/
public Student findById(int id) throws Exception
SqlSession sqlSession = null;
try
sqlSession = MybatisUtil.getSqlSession();
return sqlSession.selectOne("studentNamespace.findById",id);
catch(Exception e)
e.printStackTrace();
throw e;
finally
MybatisUtil.closeSqlSession();
public static void main(String[] args) throws Exception
StudentCardDao dao = new StudentCardDao();
Student student = dao.findById(1);
System.out.println(student.getId()+":"+student.getName());
System.out.println(student.getCard().getId()+":"+student.getCard().getNum());
mybatis一对多映射【班级与学生】
创建grades.sql和students.sql
drop table students;
drop table grades;
create table grades(
gid int(5) primary key,
gname varchar(10)
);
create table students(
sid int(5) primary key,
sname varchar(10),
sgid int(5),
constraint sgid_fk foreign key(sgid) references grades(gid)
);
insert into grades(gid,gname) values(1,'java');
insert into students(sid,sname,sgid) values(1,'哈哈',1);
insert into students(sid,sname,sgid) values(2,'呵呵',1);创建Grade.java和Student.sql
/**
* 班级（单方）
* @author csx
*/
public class Grade
private Integer id;
private String name;
private List<Student> studentList = new ArrayList<Student>();
public Grade()
public Integer getId()
return id;
public void setId(Integer id)
this.id = id;
public String getName()
return name;
public void setName(String name)
this.name = name;
public List<Student> getStudentList()
return studentList;
public void setStudentList(List<Student> studentList)
this.studentList = studentList;
/**
* 学生（多方）
* @author csx
*/
public class Student
private Integer id;
private String name;
private Grade grade;
public Student()
public Integer getId()
return id;
public void setId(Integer id)
this.id = id;
public String getName()
return name;
public void setName(String name)
this.name = name;
public Grade getGrade()
return grade;
public void setGrade(Grade grade)
this.grade = grade;
创建GradeMapper.xml和StudentMapper.xml
<!--GradeMapper.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">
<mapper namespace="gradeNamespace">
<resultMap type="cn.csx.javaee.mybatis.one2many.Grade" id="gradeMap">
<id property="id" column="gid" />
<result property="name" column="gname"/>
<collection property="studentList" resultMap="studentNamespace.studentMap"/>
</resultMap>
<select id="findGradeByName" parameterType="string" resultMap="gradeMap">
select g.gid,g.gname,s.sid,s.sname
from grades g,students s
where g.gid = s.sgid
and s.sname = #name
</select>
</mapper>
<!--StudentMapper.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">
<mapper namespace="studentNamespace">
<resultMap type="cn.csx.javaee.mybatis.one2many.Student" id="studentMap">
<id property="id" column="sid" />
<result property="name" column="sname"/>
<association property="grade" resultMap="gradeNamespace.gradeMap"/>
</resultMap>
<select id="findAllByName" parameterType="string" resultMap="studentMap">
select s.sid,s.sname,g.gid,g.gname
from grades g,students s
where g.gid = s.sgid
and g.gname = #name
</select>
</mapper>创建GradeStudentDao.java
public class GradeStudentDao
/**
* 查询java班级有哪些【学生】
*/
public List<Student> findAllByName(String name) throws Exception
SqlSession sqlSession = null;
try
sqlSession = MybatisUtil.getSqlSession();
return sqlSession.selectList("studentNamespace.findAllByName",name);
catch(Exception e)
e.printStackTrace();
throw e;
finally
MybatisUtil.closeSqlSession();
/**
* 查询哈哈属于哪个【班级】
*/
public Grade findGradeByName(String name) throws Exception
SqlSession sqlSession = null;
try
sqlSession = MybatisUtil.getSqlSession();
return sqlSession.selectOne("gradeNamespace.findGradeByName",name);
catch(Exception e)
e.printStackTrace();
throw e;
finally
MybatisUtil.closeSqlSession();
public static void main(String[] args) throws Exception
GradeStudentDao dao = new GradeStudentDao();
List<Student> studentList = dao.findAllByName("java");
for(Student s : studentList)
System.out.println(s.getId()+":"+s.getName()+":"+s.getGrade().getId()+":"+s.getGrade().getName());
Grade grade = dao.findGradeByName("哈哈");
System.out.println(grade.getId()+":"+grade.getName());
mybatis多对多映射【学生与课程】
创建students.sql和courses.sql和middles.sql
drop table middles;
drop table students;
drop table courses;
create table students(
sid int(5) primary key,
sname varchar(10)
);
create table courses(
cid int(5) primary key,
cname varchar(10)
);
create table middles(
sid int(5),
cid int(5),
primary key(sid,cid)
);
insert into students(sid,sname) values(1,'哈哈');
insert into students(sid,sname) values(2,'呵呵');
insert into courses(cid,cname) values(1,'java');
insert into courses(cid,cname) values(2,'net');
insert into middles(sid,cid) values(1,1);
insert into middles(sid,cid) values(1,2);
insert into middles(sid,cid) values(2,1);
insert into middles(sid,cid) values(2,2);
select * from students;
select * from courses;
select * from middles;创建Student.java和Course.java
/**
* 学生(多方)
* @author csx
*/
public class Student
private Integer id;
private String name;
private List<Course> courseList = new ArrayList<Course>();
public Student()
public Integer getId()
return id;
public void setId(Integer id)
this.id = id;
public String getName()
return name;
public void setName(String name)
this.name = name;
public List<Course> getCourseList()
return courseList;
public void setCourseList(List<Course> courseList)
this.courseList = courseList;
/**
* 课程(多方)
* @author AdminTC
*/
public class Course
private Integer id;
private String name;
private List<Student> studentList = new ArrayList<Student>();
public Course()
public Integer getId()
return id;
public void setId(Integer id)
this.id = id;
public String getName()
return name;
public void setName(String name)
this.name = name;
public List<Student> getStudentList()
return studentList;
public void setStudentList(List<Student> studentList)
this.studentList = studentList;
创建StudentMapper.xml和CourseMapper.xml
<!--StudentMapper.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">
<mapper namespace="studentNamespace">
<resultMap type="cn.csx.javaee.mybatis.many2many.Student" id="studentMap">
<id property="id" column="sid" />
<result property="name" column="sname"/>
</resultMap>
<select id="findStudentByName" parameterType="string" resultMap="studentMap">
select s.sid,s.sname
from students s,middles m,courses c
where s.sid = m.sid
and m.cid = c.cid
and c.cname = #name
</select>
</mapper>
<!--CourseMapper.xml-->
<?xml version="1.0" encoding="UTF-8" ?>
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