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

1. 学生信息如下：
2. name:张三 birthday:1982-01-01
3. his teachers as follows:
4. teacher name:Jerry
5. teacher name:Tom
6. name:李四 birthday:1983-02-02
7. his teachers as follows:
8. teacher name:Jerry
9. name:王五 birthday:1984-03-03
10. his teachers as follows:
11. teacher name:Tom
12. name:赵六 birthday:1985-04-04
13. his teachers as follows:
14. 老师信息如下：
15. name:Jerry subject:语文
16. his students as follows:
17. student name:张三
18. student name:李四
19. name:Tom subject:数学
20. his students as follows:
21. student name:张三
22. student name:王五
23. name:Steven subject:英语
24. 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。