DROP TABLE IF EXISTS `student`;
create table student(
           student_id  VARCHAR(100) PRIMARY KEY,
           student_name VARCHAR(100)
);
DROP TABLE IF EXISTS `teacher`;
create table teacher(
          teacher_id VARCHAR(100) PRIMARY KEY,
          teacher_name VARCHAR(100)
);
DROP TABLE IF EXISTS `teacher_student`;
create table teacher_student(
          ts_id VARCHAR(100) PRIMARY KEY,
          teacher_id VARCHAR(100),
          student_id VARCHAR(100),
          FOREIGN KEY teacher_id references teacher(teacher_id),
          FOREIGN KEY student_id references student(student_id)
);

alter table teacher_student  add constraint  ts1   unique  nonclutered (teacher_id,student_id); 

insert into student values ('001','liufang');
insert into student values ('002','jianghaiying');
insert into student values ('003','duanhuixia');

insert into teacher values ('001','gaowei');
insert into teacher values ('002','lihua');
insert into teacher values ('003','xugang');

insert into teacher_student values('1','001','001');
insert into teacher_student values('2','002','001');
insert into teacher_student values('3','003','001');
insert into teacher_student values('4','001','002');
insert into teacher_student values('4','002','002');
insert into teacher_student values('5','003','003');

我的Ibatis配置文件为：

<?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_Teacher">

  <!-- Use type aliases to avoid typing the full classname every time. -->
  <typeAlias alias="Student_Teacher.Student" type="com.foundersoftware.wishjob.demo.ibatis.manytomany.model.Student" />
  <typeAlias alias="Student_Teacher.Teacher" type="com.foundersoftware.wishjob.demo.ibatis.manytomany.model.Teacher"/>
  <!-- Result maps describe the mapping between the columns returned
       from a query, and the class properties.  A result map isn't
       necessary if the columns (or aliases) match to the properties
       exactly. -->
  <resultMap id="studentResult_basic" class="Student_Teacher.Student">
    <result property="studentId" column="student_id" jdbcType="varchar"/>
    <result property="studentName" column="student_name" jdbcType="varchar"/>
  </resultMap>
 
  <resultMap id="studentResult" class="Student_Teacher.Student" extends="studentResult_basic" >
    <result property="teacherList" column="student_id" select="Student_Teacher.selectBystudentId" />
  </resultMap>
 
  <resultMap id="teacherResult_basic" class="Student_Teacher.Teacher">
    <result property="teacherId" column="teacher_id" jdbcType="varchar"/>
    <result property="teacherName" column="teacher_name" jdbcType="varchar"/>
   </resultMap>
  
   <resultMap id="teacherResult" class="Student_Teacher.Teacher" extends="teacherResult_basic">
    <result property="studentList" column="teacher_id" select="Student_Teacher.selectByteacherId" />
  </resultMap>
 
  <!-- select all the properies of a student including the teacherList by
     using Id-->
  <select id="SelectStudentById" parameterClass="String" resultMap="studentResult">
      select * from student where student_id = #studentId#
  </select>

  <!-- select all the properies of students including the teacherList -->
  <select id="SelectAllStudents" resultMap="studentResult">
      select * from student
  </select>
 
  <select id="selectByteacherId" parameterClass="String" resultMap="studentResult">
        select s.* from student s where s.student_id in
        (select student_id from teacher_student where teacher_id=#value#)
  </select>
   
  <select id="SelectTeacherById" parameterClass="String" resultMap="teacherResult">
      select * from teacher where teacher_id = #teacherId#
  </select>
 
 
  <select id="selectBystudentId" parameterClass="String" resultMap="teacherResult">
        select t.* from Teacher t where t.teacher_id in
        (select teacher_id from teacher_student where student_id=#value#)
  </select>
 
  <!-- Insert example, using the Student parameter class -->
  <insert id="insertStudent" parameterClass="Student_Teacher.Student" >
    insert into student (
    student_id,
    student_name)
    values(#studentId#,#studentName#)
  </insert> 
 
  <!-- Update example, using the Student parameter class -->
  <update id="updateStudent" parameterClass="Student_Teacher.Student">
    update student set
      student_name = #studentName#
    where
      student_id = #studentId#
  </update>
 
   <!-- Delete example, using an integer as the parameter class -->
  <delete id="deleteStudentById" parameterClass="string">
    delete from student where student_id = #student_id#
  </delete>
</sqlMap>

我有两个Model类，分别为：

package com.foundersoftware.wishjob.demo.ibatis.manytomany.model;

import java.util.ArrayList;
import java.util.List;

public class Student {
 
 private String studentId;
 
 private String studentName;
 
 private List<Teacher> teacherList = new ArrayList<Teacher>();
 
 public String getStudentId() {
  return studentId;
 }

 public void setStudentId(String studentId) {
  this.studentId = studentId;
 }

 public String getStudentName() {
  return studentName;
 }

 public void setStudentName(String studentName) {
  this.studentName = studentName;
 }

  public String toString() {
         return "Student{" +
                 "studentId=" + studentId +
                 ", studentName='" + studentName + '\'' +
                 ", TeacherList='" + teacherList.size() + '\'' +
                 '}';
     }

     public String out() {
         StringBuffer sb = new StringBuffer();
         sb.append("Student{" +
                 "studentId=" + studentId +
                 ", studentName='" + studentName + '\'' +
                 ", TeacherList='" + teacherList.size() + '\'');
         for (Teacher teacher : teacherList) {
             sb.append("\n\t").append(teacher.toString());
         }
         return sb.toString();
}
}

和

package com.foundersoftware.wishjob.demo.ibatis.manytomany.model;

import java.util.ArrayList;
import java.util.List;

public class Teacher {
 
 private String teacherId;
 
 private String teacherName;
 
 private List<Student> studentList= new ArrayList<Student>();
 
 public String getTeacherId() {
  return teacherId;
 }

 public void setTeacherId(String teacherId) {
  this.teacherId = teacherId;
 }

 public String getTeacherName() {
  return teacherName;
 }

 public void setTeacherName(String teacherName) {
  this.teacherName = teacherName;
 }
 
  public String toString() {
         return "Teacher{" +
                 "teacherId=" + teacherId +
                 ", teacherName='" + teacherName + '\'' +
                 ", studentList=" + studentList.size() +
                 '}';
     }

     public String out(){
         StringBuffer sb= new StringBuffer();
         if(studentList.size()>0){
             sb.append("Teacher{" +
                 "teacherId=" + teacherId +
                 ", teacherName='" + teacherName + '\'' +
                 ", studentList=" + studentList.size());
             for(Student s: studentList){
                 sb.append("\n\t").append(s.toString());
             }
             sb.append("\n}");
         }
         return sb.toString();
     }
 
}

我的DAO层为：

package com.foundersoftware.wishjob.demo.ibatis.manytomany.dao;

import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

import com.foundersoftware.wishjob.demo.ibatis.manytomany.model.*;
import com.foundersoftware.wishjob.util.SqlMapFactory;
import com.ibatis.sqlmap.client.SqlMapClient;

public class Student_TeacherDAOIbatisImpl  {

//我的SqlMapFactory工具类已经在Ibatis单表的文章中给出了~！
 private static SqlMapClient sqlMapper = SqlMapFactory.getInstance();

 public void add(Student student) {
  try {
   sqlMapper.insert("Student_Teacher.insertStudent", student);
  } catch (SQLException e) {
   e.printStackTrace();
  }
  
 }

 public void update(Student student) {
  try {
   sqlMapper.update("Student_Teacher.updateStudent", student);
  } catch (SQLException e) {
   e.printStackTrace();
  } 
 }

 @SuppressWarnings("unchecked")
 public List<Student> query() {
  List <Student>list = new ArrayList<Student>();
  try {
   list = sqlMapper.queryForList("Student_Teacher.SelectAllStudents");
  } catch (SQLException e) {
   e.printStackTrace();
  }
  return list;
 }

 public void delete(String student_id) {
  try {
   sqlMapper.delete("Student_Teacher.deleteStudentById", student_id);
  } catch (SQLException e) {
   e.printStackTrace();
  }
 }

 public Student getStudentById(String student_id) {
  Student student = new Student();
  try {
   student = (Student) sqlMapper.queryForObject("Student_Teacher.SelectStudentById", student_id);
  } catch (SQLException e) {
   e.printStackTrace();
  }
  return student;
 }
}

 我的Test为：

package com.foundersoftware.wishjob.demo.ibatis.manytomany.test;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import com.foundersoftware.wishjob.demo.ibatis.manytomany.dao.Student_TeacherDAOIbatisImpl;
import com.foundersoftware.wishjob.demo.ibatis.manytomany.model.*;
public class ManytomanyTest {
 
 public static void main(String[] args){
  
  Student_TeacherDAOIbatisImpl test = new Student_TeacherDAOIbatisImpl();
  List<Student> student = new ArrayList<Student>();
  try{
   //select all students from the table "student"!
   student = test.query();
   Iterator<Student> it=student.iterator();
   System.out.println("select all students from table student:");
         while(it.hasNext()){
          Student s1=(Student)it.next();
          System.out.println(s1.out());;
         }
        
         //select all the properties of a student including the teacherList by
   //using the StudentId("001")
   Student studentTest = test.getStudentById("001");
   System.out.println(studentTest.out());
        
         //insert student
         Student s2= new Student();
         s2.setStudentId("004");
         s2.setStudentName("liqie");
         test.add(s2);
         System.out.println("insert sucess");
        
         //update student
         Student s3=test.getStudentById("001");
         s3.setStudentName("duanhuixia");
         test.update(s3);
         System.out.println("update sucess");
        
         //delete student
         Student s4=test.getStudentById("003");
         test.delete(s4.getStudentId());
         System.out.println("delete sucess");
        
  }catch(Exception e){
   e.printStackTrace();
  }
 }

}

我也是刚刚开始学习Ibatis，大家互相进步啊！

DROP TABLE IF EXISTS `student`;
create table student(
           student_id  VARCHAR(100) PRIMARY KEY,
           student_name VARCHAR(100)
);

insert into student values ('001','liufang');
insert into student values ('002','jianghaiying');
insert into student values ('003','duanhuixia');

 Ibatis配置文件为：

<?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">

  <!-- Use type aliases to avoid typing the full classname every time. -->
  <typeAlias alias="Student.Student" type="com.foundersoftware.wishjob.demo.ibatis.crud.model.Student"/>

  <!-- Result maps describe the mapping between the columns returned
       from a query, and the class properties.  A result map isn't
       necessary if the columns (or aliases) match to the properties
       exactly. -->
  <resultMap id="studentResult" class="Student.Student">
    <result property="studentId" column="student_id" jdbcType="varchar"/>
    <result property="studentName" column="student_name" jdbcType="varchar"/>
  </resultMap>

  <!-- the cacheModel of ibatis!
  if you don't excute "insertStudent" "updateStudent"
  and "deleteStudentById",the result will be saved in cache for 24 hours-->
  <cacheModel id="student-cache" type="LRU">
     <flushInterval hours="24"/>
     <flushOnExecute statement="Student.insertStudent"/>
     <flushOnExecute statement="Student.updateStudent"/>
     <flushOnExecute statement="Student.deleteStudentById"/>
     <property name="size" value="1000"/>
  </cacheModel>
 
  <!-- Select with no parameters using the result map for Student class. -->
  <select id="selectAllStudentes" resultMap="studentResult" cacheModel="student-cache" >
    select * from student
  </select>

 <!-- A simpler select example without the result class.    -->
  <select id="selectStudentById" parameterClass="string"  resultMap="studentResult" cacheModel="student-cache">
    select
      student_id,
      student_name
    from student
    where student_id = #student_id#
  </select>
 
  <!-- Insert example, using the Student parameter class -->
   <insert id="insertStudent" parameterClass="Student.Student" >
    insert into student (
    student_id,
    student_name)
    values(#studentId#,#studentName#)
  </insert>
 
  <!-- Update example, using the Student parameter class -->
  <update id="updateStudent" parameterClass="Student.Student">
    update student set
      student_name = #studentName#
    where
      student_id = #studentId#
  </update>
 
  <!-- Delete example, using an integer as the parameter class -->
  <delete id="deleteStudentById" parameterClass="string">
    delete from student where student_id = #student_id#
  </delete>
</sqlMap>

package com.foundersoftware.wishjob.demo.ibatis.crud.model;

public class Student {

private String studentId;
 
 private String studentName;
 
 public String getStudentId() {
  return studentId;
 }

 public void setStudentId(String studentId) {
  this.studentId = studentId;
 }

 public String getStudentName() {
  return studentName;
 }

 public void setStudentName(String studentName) {
  this.studentName = studentName;
 }

}

我的DAO类为：

package com.foundersoftware.wishjob.demo.ibatis.crud.dao;

import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

import com.foundersoftware.wishjob.demo.ibatis.crud.model.Student;
import com.foundersoftware.wishjob.util.SqlMapFactory;
import com.ibatis.sqlmap.client.SqlMapClient;

public class StudentIbatisDAO {
 
 /**
    * SqlMapClient instances are thread safe, so you only need one.
    * In this case, we'll use a static singleton.  So sue me.  ;-)
    */
     private static SqlMapClient sqlMapper = SqlMapFactory.getInstance();

  public void add(Student student) {
   try {
    sqlMapper.insert("Student.insertStudent", student);
   } catch (SQLException e) {
    e.printStackTrace();
   }
   
  }

  public void update(Student student) {
   try {
    sqlMapper.update("Student.updateStudent", student);
   } catch (SQLException e) {
    e.printStackTrace();
   } 
  }

  @SuppressWarnings("unchecked")
  public List<Student> query() {
   List <Student>list = new ArrayList<Student>();
   try {
    list = sqlMapper.queryForList("Student.selectAllStudentes");
   } catch (SQLException e) {
    e.printStackTrace();
   }
   return list;
  }

  public void delete(String student_id) {
   try {
    sqlMapper.delete("Student.deleteStudentById", student_id);
   } catch (SQLException e) {
    e.printStackTrace();
   }
  }

  public Student getStudentById(String student_id) {
   Student student = new Student();
   try {
    student = (Student) sqlMapper.queryForObject("Student.selectStudentById", student_id);
   } catch (SQLException e) {
    e.printStackTrace();
   }
   return student;
  }

}

从上面可以看到我用了一个SqlMapFactory的工具类，在这里和大家一起分享！

package com.foundersoftware.wishjob.util;

import java.io.IOException;
import java.io.Reader;
import com.ibatis.common.resources.Resources;
import com.ibatis.sqlmap.client.SqlMapClient;
import com.ibatis.sqlmap.client.SqlMapClientBuilder;

public class SqlMapFactory {
 
 private static final SqlMapClient sqlMap;
 static {
  try {
   String resource = "com/foundersoftware/wishjob/config/sqlmap-config.xml";
   Reader reader = Resources.getResourceAsReader (resource);
   sqlMap = SqlMapClientBuilder.buildSqlMapClient(reader);
  } catch (Exception e) {
   e.printStackTrace();
   throw new RuntimeException ("Error initializing MyAppSqlConfig class. Cause: " + e);
  }
 }
  
 public static SqlMapClient getSqlMapInstance () {
  return sqlMap;
  }
 public static SqlMapClient getInstance () {
  return sqlMap;
  }
 public static SqlMapClient getInstance1() {
  String resource = "com/foundersoftware/wishjob/config/sqlmap-config.xml";
  Reader reader;
  SqlMapClient sqlMap = null;
  
  try {
   reader = Resources.getResourceAsReader(resource);
   sqlMap = SqlMapClientBuilder.buildSqlMapClient(reader);
  } catch (IOException e) {
   e.printStackTrace();
  }
  return sqlMap;
 }
}

我的Test类为：

package com.foundersoftware.wishjob.demo.ibatis.crud.test;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import com.foundersoftware.wishjob.demo.ibatis.crud.dao.StudentIbatisDAO;
import com.foundersoftware.wishjob.demo.ibatis.crud.model.Student;
public class CrudTest {
 
 public static void main(String[] args){
  
  StudentIbatisDAO test = new StudentIbatisDAO();
  List<Student> student = new ArrayList<Student>();
  try{
   //select all students from the table "student"!
   student = test.query();
   Iterator<Student> it=student.iterator();
   System.out.println("select all students from table student:");
         while(it.hasNext()){
          Student s1=(Student)it.next();
          System.out.println(s1.getStudentId()+"->"+s1.getStudentName());
         }
        
         //select studentName from table "student" by studentId
         System.out.println("select studentName from table student by studentId(001):");
         Student s2=test.getStudentById("001");
         System.out.println(s2.getStudentName());
        
         //insert student
         Student s3= new Student();
         s3.setStudentId("004");
         s3.setStudentName("jianghaiying");
         test.add(s3);
         System.out.println("insert sucess");
        
         //update student
         Student s4=test.getStudentById("002");
         s4.setStudentName("duanhuixia");
         test.update(s4);
         System.out.println("update sucess");
        
         //delete student
         Student s5=test.getStudentById("003");
         test.delete(s5.getStudentId());
         System.out.println("delete sucess");
        
  }catch(Exception e){
   e.printStackTrace();
  }
 }

}

大家如果有什么疑问可以一起讨论啊！我也是新手啊！

drop table if exists 'student`;
create table student(
           student_id  VARCHAR(100) PRIMARY KEY,
           student_name VARCHAR(100),
           specialty_id VARCHAR(100),
           FOREIGN KEY specialty_id references specialty(specialty_id)
);
drop table if exists  'specialty';
create table specialty(
           specialty_id VARCHAR(100) PRIMARY KEY,
           specialty_name VARCHAR(100)
);

insert into student values ('001','liufang','001');
insert into student values ('002','jianghaiying','001');
insert into student values ('003','duanhuixia','001');

insert into specialty values ('001','English');
insert into specialty values ('002','French');
insert into specialty values ('003','Japanese');

Ibatis中的配置文件为：
OnetoMany.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_Specialty">

  <!-- Use type aliases to avoid typing the full classname every time. -->
  <typeAlias alias="Student_Specialty.Student" type="com.foundersoftware.wishjob.demo.ibatis.onetomany.model.Student"/>
  <typeAlias alias="Specialty" type="com.foundersoftware.wishjob.demo.ibatis.onetomany.model.Specialty"/>
 
  <!-- Result maps describe the mapping between the columns returned
       from a query, and the class properties.  A result map isn't
       necessary if the columns (or aliases) match to the properties
       exactly. -->
  <resultMap id="studentResult" class="Student_Specialty.Student">
    <result property="studentId" column="student_id" jdbcType="varchar"/>
    <result property="studentName" column="student_name" jdbcType="varchar"/>
    <result property="specialty" column="specialty_id" select="Student_Specialty.selectSpecialtyById"/>
  </resultMap>
 
  <resultMap id="specialtyResult" class="Specialty">
    <result property="specialtyId" column="specialty_id" jdbcType="varchar"/>
    <result property="specialtyName" column="specialty_name" jdbcType="varchar"/>
  </resultMap>
 
  <!-- the cacheModel of ibatis!if you don't excute "insertStudent" "updateStudent"
  and "deleteStudentById",the result will be saved in cache for 24 hours-->
  <cacheModel id="student-specialty-cache" type="LRU">
     <flushInterval hours="24"/>
     <flushOnExecute statement="Student_Specialty.insertStudent"/>
     <flushOnExecute statement="Student_Specialty.updateStudent"/>
     <flushOnExecute statement="Student_Specialty.deleteStudentById"/>
     <property name="size" value="1000"/>
  </cacheModel>
   
  <!-- Select with no parameters using the result map for Student class. -->
  <select id="selectAllStudents" resultMap="studentResult" cacheModel="student-specialty-cache" >
    select * from student
  </select>

 <!-- A simpler select example without the result class.    -->
  <select id="selectSpecialtyById" parameterClass="string" resultMap="specialtyResult" cacheModel="student-specialty-cache">
    select
      specialty_id,
      specialty_name
    from specialty
    where specialty_id = #specialty_id#
  </select>
 
 <!-- A simpler select example without the result class.    -->
  <select id="selectStudentById" parameterClass="string" resultMap="studentResult" cacheModel="student-specialty-cache">
    select
      student_id,
      student_name,
      specialty_id
    from student
    where student_id = #student_id#
  </select>
 
  <!-- Insert example, using the Student parameter class -->
  <insert id="insertStudent" parameterClass="Student_Specialty.Student" >
    insert into student (
    student_id,
    student_name,
    specialty_id)
    values(#studentId#,#studentName#,#specialty.specialtyId#)
  </insert>
 
  <!-- Update example, using the Student parameter class -->
  <update id="updateStudent" parameterClass="Student_Specialty.Student">
    update student set
      student_name = #studentName#,
      specialty_id = #specialty.specialtyId#
    where
      student_id = #studentId#
  </update>
 
  <!-- Delete example, using an integer as the parameter class -->
  <delete id="deleteStudentById" parameterClass="string">
    delete from student where student_id = #student_id#
  </delete>
</sqlMap>

用到的两个Model类：

package com.foundersoftware.wishjob.demo.ibatis.onetomany.model;

public class Student {

    private String studentId;
 
 private String studentName;
 
 private Specialty specialty;
 
 public String getStudentId() {
  return studentId;
 }

 public void setStudentId(String studentId) {
  this.studentId = studentId;
 }

 public String getStudentName() {
  return studentName;
 }

 public void setStudentName(String studentName) {
  this.studentName = studentName;
 }

 public Specialty getSpecialty() {
  return specialty;
 }

 public void setSpecialty(Specialty specialty) {
  this.specialty = specialty;
 }
}

package com.foundersoftware.wishjob.demo.ibatis.onetomany.model;

public class Specialty {

 private String specialtyId;
 
 private String specialtyName;

 public String getSpecialtyId() {
  return specialtyId;
 }

 public void setSpecialtyId(String specialtyId) {
  this.specialtyId = specialtyId;
 }

 public String getSpecialtyName() {
  return specialtyName;
 }

 public void setSpecialtyName(String specialtyName) {
  this.specialtyName = specialtyName;
 }
}

一个DAO类为：

package com.foundersoftware.wishjob.demo.ibatis.onetomany.dao;

import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

import com.foundersoftware.wishjob.demo.ibatis.onetomany.model.Student;
import com.foundersoftware.wishjob.demo.ibatis.onetomany.model.Specialty;
import com.foundersoftware.wishjob.util.SqlMapFactory;
import com.ibatis.sqlmap.client.SqlMapClient;

public class Student_SpecialtyIbatisDAO {
 
 /**
    * SqlMapClient instances are thread safe, so you only need one.
    * In this case, we'll use a static singleton.  So sue me.  ;-)
    */
  //这个用到了一个工具类SqlMapFactory，这个在我的Ibatis单表操作中以写出了！
     private static SqlMapClient sqlMapper = SqlMapFactory.getInstance();

  public void add(Student student) {
   try {
    sqlMapper.insert("Student_Specialty.insertStudent", student);
   } catch (SQLException e) {
    e.printStackTrace();
   }
   
  }

  public void update(Student student) {
   try {
    sqlMapper.update("Student_Specialty.updateStudent", student);
   } catch (SQLException e) {
    e.printStackTrace();
   } 
  }

  @SuppressWarnings("unchecked")
  public List<Student> query() {
   List <Student>list = new ArrayList<Student>();
   try {
    list = sqlMapper.queryForList("Student_Specialty.selectAllStudents");
   } catch (SQLException e) {
    e.printStackTrace();
   }
   return list;
  }

  public void delete(String student_id) {
   try {
    sqlMapper.delete("Student_Specialty.deleteStudentById", student_id);
   } catch (SQLException e) {
    e.printStackTrace();
   }
  }

  public Student getStudentById(String student_id) {
   Student student = new Student();
   try {
    student = (Student) sqlMapper.queryForObject("Student_Specialty.selectStudentById", student_id);
   } catch (SQLException e) {
    e.printStackTrace();
   }
   return student;
  }
  
  public Specialty getSpecialtyById(String specialty_id) {
   Specialty specialty = new Specialty();
   try {
    specialty = (Specialty) sqlMapper.queryForObject("Student_Specialty.selectSpecialtyById", specialty_id);
   } catch (SQLException e) {
    e.printStackTrace();
   }
   return specialty;
  }
}

一个测试类：

package com.foundersoftware.wishjob.demo.ibatis.onetomany.test;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import com.foundersoftware.wishjob.demo.ibatis.onetomany.dao.Student_SpecialtyIbatisDAO;
import com.foundersoftware.wishjob.demo.ibatis.onetomany.model.Specialty;
import com.foundersoftware.wishjob.demo.ibatis.onetomany.model.Student;

public class OnetomanyTest {
 
 public static void main(String[] args){
  
  Student_SpecialtyIbatisDAO test = new Student_SpecialtyIbatisDAO();
  List<Student> student = new ArrayList<Student>();
  try{
   //select all students from the table "student"!
   student = test.query();
   Iterator<Student> it=student.iterator();
   System.out.println("select all students from table student:");
         while(it.hasNext()){
          Student s1=(Student)it.next();
          System.out.println(s1.getStudentId()+"->"+s1.getStudentName()+"->"+s1.getSpecialty().getSpecialtyName());
         }
        
         //select studentName from table "student" by studentId
         System.out.println("select studentName from table student by studentId(001):");
         Student s2=test.getStudentById("001");
         System.out.println(s2.getStudentName()+"->"+s2.getSpecialty().getSpecialtyName());
        
         //insert student
         Student s3= new Student();
         s3.setStudentId("004");
         s3.setStudentName("jianghaiying");
         Specialty specialty = test.getSpecialtyById("002");
         s3.setSpecialty(specialty);
         test.add(s3);
         System.out.println("insert sucess");
        
         //update student
         Student s4=test.getStudentById("003");
         s4.setStudentName("duanhuixia");
         test.update(s4);
         System.out.println("update sucess");
        
         //delete student
         Student s5=test.getStudentById("001");
         test.delete(s5.getStudentId());
         System.out.println("delete sucess");
        
  }catch(Exception e){
   e.printStackTrace();
  }
 }

}

可以直接使用啊！