iBATIS的多对多 数据库设计及实现

iBATIS的多对多映射配置方法和多对一映射配置方法差不多，不同的是，多对多映射，数据库设计上需要一个记录两个类关系的中间表，本文以学生-老师为例，在iBATIS的sqlmap中配置多对多关系。

iBATIS的多对多映射配置1，建表。数据库中三个表，分别为：

CREATE TABLE [student] (
[id] [int] IDENTITY (1, 1) NOT NULL ,
[name] [nvarchar] (50) COLLATE Chinese_PRC_CI_AS NOT NULL ,
[birthday] [nvarchar] (50) COLLATE Chinese_PRC_CI_AS NOT NULL ,
CONSTRAINT [PK_student] PRIMARY KEY  CLUSTERED
(
[id]
)  ON [PRIMARY]
) ON [PRIMARY]
GO
--------------------------------------------------
CREATE TABLE [teacher] (
[id] [int] IDENTITY (1, 1) NOT NULL ,
[name] [nvarchar] (50) COLLATE Chinese_PRC_CI_AS NOT NULL ,
[subject] [nvarchar] (50) COLLATE Chinese_PRC_CI_AS NOT NULL ,
CONSTRAINT [PK_teacher] PRIMARY KEY  CLUSTERED
(
[id]
)  ON [PRIMARY]
) ON [PRIMARY]
GO
---------------------------------------------------
CREATE TABLE [student_teacher] (
[studentid] [int] NOT NULL ,
[teacherid] [int] NOT NULL ,
CONSTRAINT [PK_student_teacher] PRIMARY KEY  CLUSTERED
(
[studentid],
[teacherid]
)  ON [PRIMARY]
) ON [PRIMARY]
GO

iBATIS的多对多映射配置2，准备数据

insert into student(name,birthday) values('张三','1982-01-01')
insert into student(name,birthday) values('李四','1983-02-02')
insert into student(name,birthday) values('王五','1984-03-03')

insert into student(name,birthday) values('赵六','1985-04-04')
insert into teacher(name,subject) values('Jerry','语文')
insert into teacher(name,subject) values('Tom','数学')

insert into teacher(name,subject) values('Steven','英语')
insert into student_teacher(studentid,teacherid) values(1,1)
insert into student_teacher(studentid,teacherid) values(1,2)
insert into student_teacher(studentid,teacherid) values(2,1)
insert into student_teacher(studentid,teacherid) values(3,2)

iBATIS的多对多映射配置3，properties文件内容如下：

driver=com.microsoft.jdbc.sqlserver.SQLServerDriver
url=jdbc:microsoft:sqlserver://localhost:1433;SelectMethod=cursor;DatabaseName=ibatistest
username=sa
password=000

iBATIS的多对多映射配置4，总配置文件SqlMapConfig.xml内容如下：

﹤?xml version="1.0" encoding="UTF-8" ?﹥
﹤!DOCTYPE sqlMapConfig PUBLIC "-//ibatis.apache.org//DTD SQL Map Config 2.0//EN"
"http://ibatis.apache.org/dtd/sql-map-config-2.dtd"﹥

﹤sqlMapConfig﹥

﹤properties resource="com/lsm/cfg/jdbc.properties" /﹥
﹤transactionManager type="JDBC"﹥
﹤dataSource type="SIMPLE"﹥
﹤property value="${driver}" name="JDBC.Driver" /﹥
﹤property value="${url}" name="JDBC.ConnectionURL" /﹥
﹤property value="${username}" name="JDBC.Username" /﹥
﹤property value="${password}" name="JDBC.Password" /﹥
﹤/dataSource﹥
﹤/transactionManager﹥
﹤sqlMap resource="com/lsm/domain/Student.xml" /﹥
﹤sqlMap resource="com/lsm/domain/Teacher.xml" /﹥

﹤/sqlMapConfig﹥

iBATIS的多对多映射配置5，domain对象两个，Student 和 Teacher，如下：

Teacher.java

package com.lsm.domain;
import java.util.List;
public class Teacher
{
private int id;
private String name;
private String subject;
private List students; //注意这里有个List类型的students，表示一个老师对应多个学生

public List getStudents()
{
return students;
}
public void setStudents(List students)
{
this.students = students;
}
//省略掉其他的getter and setter
}

//Student.java
package com.lsm.domain;

import java.util.List;

public class Student
{
private int id;
private String name;
private String birthday;
private List teachers; //这里有一个list类型的teachers，表示一个学生有多个老师

public List getTeachers()
{
return teachers;
}
public void setTeachers(List teachers)
{
this.teachers = teachers;
}
//省略掉其他的getter and setter
}

iBATIS的多对多映射配置6，sqlmap配置文件

Teacher.xml

﹤?xml version="1.0" encoding="UTF-8" ?﹥
!DOCTYPE sqlMap PUBLIC "-//ibatis.apache.org//DTD SQL Map 2.0//EN"
"http://ibatis.apache.org/dtd/sql-map-2.dtd"﹥

﹤sqlMap namespace="teacher"﹥
﹤typeAlias alias="Teacher" type="com.lsm.domain.Teacher" /﹥
﹤typeAlias alias="Student" type="com.lsm.domain.Student" /﹥

﹤resultMap class="Teacher" id="teacherBasicResultMap"﹥
﹤result property="id" column="id"/﹥
﹤result property="name" column="name"/﹥
﹤result property="subject" column="subject"/﹥
﹤/resultMap﹥
﹤!-- 下面这个resultMap中有个students属性，这个结果映射继承自上面的结果映射
由于有了继承，结果映射可以任意扩展--﹥
﹤resultMap class="Teacher" id="teacherWithTeacherResultMap" extends="teacherBasicResultMap"﹥
﹤result property="students" column="id" select="getStudentsByTeacherId"/﹥
﹤/resultMap﹥
﹤!-- 这个查询中使用到了上面定义的结果映射，从而决定了查询出来的Teacher中关联出相关的students，在student.xml中配置相似，不再注释。--﹥
﹤select id="getTeachers" resultMap="teacherWithTeacherResultMap"﹥
﹤!--[CDATA[
select * from teacher
]]﹥
﹤/select﹥

﹤select id="getStudentsByTeacherId" resultClass="Student"﹥
﹤![CDATA[
select s.* from student s,student_teacher st where s.id=st.studentid and st.teacherid=#value#   ]]--﹥
﹤/select﹥

﹤/sqlMap﹥

tudent.xml

﹤?xml version="1.0" encoding="UTF-8" ?﹥
!DOCTYPE sqlMap PUBLIC "-//ibatis.apache.org//DTD SQL Map 2.0//EN"
"http://ibatis.apache.org/dtd/sql-map-2.dtd"﹥

﹤sqlMap namespace="student"﹥
﹤typeAlias alias="Student" type="com.lsm.domain.Student" /﹥
﹤typeAlias alias="Teacher" type="com.lsm.domain.Teacher" /﹥

﹤resultMap class="Student" id="studentBasicResultMap"﹥
﹤result property="id" column="id"/﹥
﹤result property="name" column="name"/﹥
﹤result property="birthday" column="birthday"/﹥
﹤/resultMap﹥

﹤resultMap class="Student" id="studentWithTeacherResultMap" extends="studentBasicResultMap"﹥
﹤result property="teachers" column="id" select="getTeachersByStudentId"/﹥
﹤/resultMap﹥

﹤select id="getStudents" resultMap="studentWithTeacherResultMap"﹥
﹤!--[CDATA[
select * from student
]]﹥
﹤/select﹥

﹤select id="getTeachersByStudentId" resultClass="Teacher"﹥
﹤![CDATA[
select t.* from teacher t,student_teacher st where t.id=st.teacherid and st.studentid=#value#   ]]--﹥
﹤/select﹥

﹤/sqlMap﹥

iBATIS的多对多映射配置7，测试

package com.lsm.test;

import java.io.Reader;
import java.sql.SQLException;
import java.util.List;
import com.ibatis.common.resources.Resources;
import com.ibatis.sqlmap.client.SqlMapClient;
import com.ibatis.sqlmap.client.SqlMapClientBuilder;
import com.lsm.domain.Student;
import com.lsm.domain.Teacher;

public class Many2Many
{

private static SqlMapClient sqlMapClient = null;
static
{
try
{
Reader reader = Resources.getResourceAsReader("com/lsm/cfg/SqlMapConfig.xml");
sqlMapClient = SqlMapClientBuilder.buildSqlMapClient(reader);
}
catch(Exception e)
{
e.printStackTrace();
}
}
/**
* @param args
*/
public static void main(String[] args)
{
Many2Many m2m = new Many2Many();
List studentlist = null;
studentlist = m2m.getStudentInfo();
for(int i=0;i﹤studentlist.size();i++)
{
Student s = new Student();
s = (Student) studentlist.get(i);
System.out.println("name:"+s.getName() + "\t" + "birthday:"+s.getBirthday());
List tlist = s.getTeachers();
if(tlist!=null)
{
System.out.println("his teachers as follows:");
{
for(int ti=0;ti﹤tlist.size();ti++)
{
Teacher t = new Teacher();
t = (Teacher) tlist.get(ti);
System.out.println("teacher name:" + t.getName());
}
}
}
}

List teacherlist = null;
teacherlist = m2m.getTeacherInfo();
for(int i=0;i﹤teacherlist.size();i++)
{
Teacher t = new Teacher();
t = (Teacher) teacherlist.get(i);
System.out.println("name:"+t.getName() + "\t" + "subject:" + t.getSubject());
List slist = t.getStudents();
if(slist!=null)
{
System.out.println("his students as follows:");
for(int si=0;si﹤slist.size();si++)
{
Student s = new Student();
s = (Student) slist.get(si);
System.out.println("student name:"+s.getName());
}
}
}
}

// 获取学生信息
public List getStudentInfo()
{
List studentList = null;
try
{
System.out.println("学生信息如下：");
studentList = sqlMapClient.queryForList("getStudents");
}
catch (SQLException e)
{
e.printStackTrace();
}
return studentList;
}

// 获取老师信息
//  获取学生信息
public List getTeacherInfo()
{
List studentList = null;
try
{
System.out.println("老师信息如下：");
studentList = sqlMapClient.queryForList("getTeachers");
}
catch (SQLException e)
{
e.printStackTrace();
}
return studentList;
}

}

8，输出

学生信息如下：

name:张三 birthday:1982-01-01

his teachers as follows:

teacher name:Jerry

teacher name:Tom

name:李四 birthday:1983-02-02

his teachers as follows:

teacher name:Jerry

name:王五 birthday:1984-03-03

his teachers as follows:

teacher name:Tom

name:赵六 birthday:1985-04-04

his teachers as follows:

老师信息如下：

name:Jerry subject:语文

his students as follows:

student name:张三

student name:李四

name:Tom subject:数学

his students as follows:

student name:张三

student name:王五

name:Steven subject:英语

his students as follows:

查询学生时带出老师信息，查询老师时带出学生信息，说明多对多映射成功。

iBATIS的多对多映射配置的情况就向你介绍到这里，希望对你有所帮助。