一：总结说明

1.需求

　　根据classId查询出对应的班级信息，包括学生和老师。

 

2.结构目录

 

3.新建学生表

1 CREATE TABLE student( 2     s_id INT PRIMARY KEY AUTO_INCREMENT, 3     s_name VARCHAR(20), 4     class_id INT 5 ); 6 INSERT INTO student(s_name,class_id) VALUES('xs1',1); 7 INSERT INTO student(s_name,class_id) VALUES('xs2',1); 8 INSERT INTO student(s_name,class_id) VALUES('xs3',1); 9 INSERT INTO student(s_name,class_id) VALUES('xs4',2);10 INSERT INTO student(s_name,class_id) VALUES('xs5',2);11 INSERT INTO student(s_name,class_id) VALUES('xs6',2);

 

4.实体类Student.java

1 package com.jun.bean; 2  3 public class Student { 4     // 5     private int id; 6     private String name; 7     // 8     public Student() {} 9     public Student(int id,String name) {10         this.id=id;11         this.name=name;12     }13     public int getId() {14         return id;15     }16     public void setId(int id) {17         this.id = id;18     }19     public String getName() {20         return name;21     }22     public void setName(String name) {23         this.name = name;24     }25     @Override26     public String toString() {27         return "Student [id=" + id + ", name=" + name + "]";28     }29     30 }

 

5.修改Classes.java类

　　因为classes除了老师，现在需要添加一个属性学生，这个学生的属性是List。

　　需要修改get set方法，修改构造函数，修改tostring方法。

1 package com.jun.bean; 2  3 import java.util.List; 4  5 public class Classes { 6     // 7     private int id; 8     private String name; 9     private Teacher teacher;10     private List
     
       list;     //新添加的属性11     //12     public Classes() {}13     public Classes(int id,String name,Teacher teacher,List
      
        list) {14         this.id=id;15         this.name=name;16         this.teacher=teacher;17         this.list=list;18     }19     public int getId() {20         return id;21     }22     public void setId(int id) {23         this.id = id;24     }25     public String getName() {26         return name;27     }28     public void setName(String name) {29         this.name = name;30     }31     public Teacher getTeacher() {32         return teacher;33     }34     public void setTeacher(Teacher teacher) {35         this.teacher = teacher;36     }37     public List
       
         getList() {38         return list;39     }40     public void setList(List
        
          list) {41         this.list = list;42     }43     @Override44     public String toString() {45         return "Classes [id=" + id + ", name=" + name + ", teacher=" + teacher + ", list=" + list + "]";46     }47         48 }
        
       
      
     

 

6.Configuration.xml

1 
      2  3  4 
     
       5   
      
        6     
       
         7       
        
          8         
          9       
        10       
        
         11         
         12         
         13         
         14         
         15       
        16     
       17   
      18 19    
      
       20       
       21    
      22 23 
     

 

二：第一种方式

1.映射文件class.xml

1 
      2  5 
     
       6     
      10     
      11         Select * from class c,teacher t,student s where c.teacher_id=t.t_id and c.c_id=s.class_id and c.c_id=#{id}12     13     
      
       14         
       15         
       16         
       
        17             
        18             
        19         
       20         
       
        21             
        22             
        23         
       24     
      25 
     

 

2.测试类

1 package com.jun.main; 2  3 import java.io.IOException; 4 import java.io.Reader; 5  6 import org.apache.ibatis.io.Resources; 7 import org.apache.ibatis.session.SqlSession; 8 import org.apache.ibatis.session.SqlSessionFactory; 9 import org.apache.ibatis.session.SqlSessionFactoryBuilder;10 import org.junit.Test;11 import com.jun.bean.Classes;12 public class MainTest {13     /**14      * 方式一15      * @throws Exception16      */17     @Test18     public void test1() throws Exception {19         Reader reader=Resources.getResourceAsReader("com/jun/config/Configuration.xml");20         SqlSessionFactory sqlSessionFactory=new SqlSessionFactoryBuilder().build(reader);21         SqlSession sqlSession=sqlSessionFactory.openSession(true);                //true后是自动提交22         String statement="one2many.selectAll";23         Classes classes=sqlSession.selectOne(statement, 1);24         System.out.println(classes);25         sqlSession.close();26     }27     28 }

 

3.测试结果

　　

 

三：方式二

1.映射文件

1 
      2  5 
     
       6     
      10     
      11         Select * from class c,teacher t,student s where c.teacher_id=t.t_id and c.c_id=s.class_id and c.c_id=#{id}12     13     
      
       14         
       15         
       16         
       
        17             
        18             
        19         
       20         
       
        21             
        22             
        23         
       24     
      25     26     
      33      
      34          select * from class where c_id=#{id}35      36      
            
       37          select t_id id,t_name name from teacher where t_id=#{id}38      39      
            
       40          select s_id id,s_name name from student where class_id=#{id} 
       41      42      
      
       43          
       44         
       45         
       46         
       47      
      48 
     

 

2.测试类

1 package com.jun.main; 2  3 import java.io.IOException; 4 import java.io.Reader; 5  6 import org.apache.ibatis.io.Resources; 7 import org.apache.ibatis.session.SqlSession; 8 import org.apache.ibatis.session.SqlSessionFactory; 9 import org.apache.ibatis.session.SqlSessionFactoryBuilder;10 import org.junit.Test;11 import com.jun.bean.Classes;12 public class MainTest {13     /**14      * 方式一15      * @throws Exception16      */17     @Test18     public void test1() throws Exception {19         Reader reader=Resources.getResourceAsReader("com/jun/config/Configuration.xml");20         SqlSessionFactory sqlSessionFactory=new SqlSessionFactoryBuilder().build(reader);21         SqlSession sqlSession=sqlSessionFactory.openSession(true);                //true后是自动提交22         String statement="one2many.selectAll";23         Classes classes=sqlSession.selectOne(statement, 1);24         System.out.println(classes);25         sqlSession.close();26     }27     /**28      * 方式二29      * @throws Exception30      */31     @Test32     public void test2() throws Exception {33         Reader reader=Resources.getResourceAsReader("com/jun/config/Configuration.xml");34         SqlSessionFactory sqlSessionFactory=new SqlSessionFactoryBuilder().build(reader);35         SqlSession sqlSession=sqlSessionFactory.openSession(true);                //true后是自动提交36         String statement="one2many.selectClass";37         Classes classes=sqlSession.selectOne(statement, 1);38         System.out.println(classes);39         sqlSession.close();40     }41     42 }

 

3.结果