【MyBatis】-----【MyBatis】---表级联系【一对一】--增删改查

一、核心配置文件

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
 3 "http://mybatis.org/dtd/mybatis-3-config.dtd">
 4 <configuration>
 5      <!-- 最开始加载引用db.properties文件 -->
 6     <properties resource="db.properties"/>
 7     <!-- 取别名    以下情况别名为类名 -->
 8      <typeAliases>
 9          <package name="com.myBatis.entity"/>
10      </typeAliases>
11     <!-- 
12         development : 开发模式
13         work : 工作模式
14      -->
15     <environments default="development">
16         <environment id="development">
17             <transactionManager type="JDBC" />
18             <!-- 配置数据库连接信息 -->
19             <dataSource type="POOLED">
20                 <property name="driver" value="${driver}" />
21                 <property name="url" value="${url}" />
22                 <property name="username" value="${username}" />
23                 <property name="password" value="${password}" />
24             </dataSource>
25         </environment>
26     </environments>
27     <!-- 引用映射文件 -->
28     <mappers >
29         <mapper resource="com/myBatis/mapper/classesMapper.xml"/>
30         <mapper resource="com/myBatis/mapper/teacherMapper.xml"/>
31     </mappers>
32 </configuration>

二、实体类

　　2.1Teacher

 1 package com.myBatis.entity;
 2 
 3 public class Teacher {
 4     // 定义实体类的属性，与teacher表中的字段对应
 5     private int id; // id===>t_id
 6     private String name; // name===>t_name
 7     public int getId() {
 8         return id;
 9     }
10     public void setId(int id) {
11         this.id = id;
12     }
13     public String getName() {
14         return name;
15     }
16     public void setName(String name) {
17         this.name = name;
18     }
19     @Override
20     public String toString() {
21         return "Teacher [id=" + id + ", name=" + name + "]";
22     }
23     public Teacher() {
24         super();
25     }
26     public Teacher(int id) {
27         super();
28         this.id = id;
29     }
30     
31     
32 }

　　2.2Classes

package com.myBatis.entity;

public class Classes {
    private int id; // id===>c_id
    private String name; // name===>c_name
    /**
     * class表中有一个teacher_id字段，所以在Classes类中定义一个teacher属性，
     * 用于维护teacher和class之间的一对一关系，通过这个teacher属性就可以知道这个班级是由哪个老师负责的
     */
    private Teacher teacher;
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Teacher getTeacher() {
        return teacher;
    }
    public void setTeacher(Teacher teacher) {
        this.teacher = teacher;
    }
    @Override
    public String toString() {
        return "Classes [id=" + id + ", name=" + name + ", teacher=" + teacher + "]";
    }
    public Classes(String name, Teacher teacher) {
        super();
        this.name = name;
        this.teacher = teacher;
    }
    public Classes() {
        super();
    }
    
    
}

三、映射文件

teacherMapper.xml

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" 
 3 "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
 4     <!-- 
 5     为这个mapper指定一个唯一的namespace，namespace的值习惯上设置成包名+sql映射文件名，
 6     这样就能够保证namespace的值是唯一的 
 7     -->
 8     <mapper namespace="com.myBatis.mapper.teacherMapper">
 9         <!-- 根据id查询得到一个user对象 -->
10         <select id="getteacher" parameterType="int" resultMap="TeacherResultMap">
11             select * from classes c, teacher t where c.t_id=t.t_id and t.t_id=#{id}
12         </select>
13         <!-- 使用resultMap映射实体类和字段之间的一一对应关系 -->
14         <resultMap type="teacher" id="TeacherResultMap">
15             <id property="id" column="t_id"/>
16             <result property="name" column="t_name"/>
17         </resultMap>
18         
19          <insert id="addTeacher" parameterType="Teacher">
20             insert into teacher values(#{t_name})
21         </insert>
22         
23     </mapper>
24

classesMapper.xml

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" 
 3 "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
 4     <!-- 
 5     为这个mapper指定一个唯一的namespace，namespace的值习惯上设置成包名+sql映射文件名，
 6     这样就能够保证namespace的值是唯一的 
 7     -->
 8     <mapper namespace="com.myBatis.mapper.classesMapper">
 9     <!-- 嵌套结果：使用嵌套结果映射来处理重复的联合结果的子集
10              封装联表查询的数据(去除重复的数据) 
11              根据id查询得到一个user对象 -->
12         <select id="getclassess" parameterType="int" resultMap="ClassResultMap">
13              select * from classes c, teacher t where c.t_id=t.t_id and c.c_id=#{id}
14         </select>
15         <!-- 使用resultMap映射实体类和字段之间的一一对应关系 -->
16         <resultMap type="Classes" id="ClassResultMap">
17             <id property="id" column="c_id"/>
18             <result property="name" column="c_name"/>
19             <association property="teacher" javaType="Teacher">
20                 <id property="id" column="t_id"/>
21                 <result property="name" column="t_name"/>
22             </association>
23         </resultMap>
24         <!--  根据id查询删除一个class 的t_id -->
25         <delete id="deleteClasses" parameterType="Classes">
26             delete from classes where c_id=#{id}
27         </delete>
28           <!-- 添加(Create) -->
29         <insert id="addClasses" parameterType="Classes">
30             insert into classes values(null,#{name},#{teacher.id})
31         </insert>
32          <!-- 修改班级所对应的老师(Update) -->
33         <update id="updateClasses" parameterType="Classes">
34             update classes set t_id=#{teacher.id} where c_id=#{id}
35         </update>
36         
37     </mapper>
38

四、测试类

 1 package myBatisTest;
 2 import org.apache.ibatis.session.SqlSession;
 3 import org.junit.Test;
 4 
 5 import com.myBatis.entity.Classes;
 6 import com.myBatis.entity.Teacher;
 7 import com.myBatis.util.myBtaisUtil;
 8 
 9 public class TestUser {
10     //修改
11     @Test
12     public void testUpdateClasses() {
13         SqlSession sqlSession=myBtaisUtil.getsqlSession();
14         //先查找
15         String selectclasses = "com.myBatis.mapper.classesMapper.getclassess";
16         Classes classes =sqlSession.selectOne(selectclasses, 3);
17         System.out.println(classes);
18          //再修改
19         Teacher teacher = new Teacher(4);
20         System.out.println();
21         classes.setTeacher(teacher);
22         String update = "com.myBatis.mapper.classesMapper.updateClasses";
23         int i = sqlSession.update(update, classes);
24          System.out.println(i);
25          Classes  classes2= sqlSession.selectOne(selectclasses, 3);
26          System.out.println(classes2);
27     }
28 
29       //添加
30     @Test
31     public void testAddClasses() {
32         SqlSession sqlSession=myBtaisUtil.getsqlSession();
33          String add = "com.myBatis.mapper.classesMapper.addClasses";
34          Classes classes = new Classes();
35          Teacher teacher= new Teacher(4);
36          classes.setName("1111");
37          classes.setTeacher(teacher);
38          int i = sqlSession.insert(add, classes);
39          System.out.println(i);
40     }
41     
42     //删除
43     @Test
44     public void testDeleteClasses() {
45         SqlSession sqlSession=myBtaisUtil.getsqlSession();
46         String delete = "com.myBatis.mapper.classesMapper.deleteClasses";
47         int i= sqlSession.delete(delete, 5);
48         System.out.println(i);
49     }
50 
51     //查询
52     @Test
53     public void testGetClasses() {
54         SqlSession sqlSession=myBtaisUtil.getsqlSession();
55         String select = "com.myBatis.mapper.classesMapper.getclassess";
56         Classes classes = sqlSession.selectOne(select, 7);
57         System.out.println(classes);
58     }
59 }

MyBatis一对一关联查询总结

　　MyBatis中使用association标签来解决一对一的关联查询，association标签可用的属性如下：

property:对象属性的名称
javaType:对象属性的类型
column:所对应的外键字段名称
select:使用另一个查询封装的结果

参考：MyBatis学习总结(五)——实现关联表查询

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【MyBatis】-----【MyBatis】---表级联系【一对一】--增删改查

MyBatis一对一关联查询总结

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