【JavaEE案例】基于MyBatis注解的学生管理程序

- 日理万妓 2024-03-26 21:13 69阅读 0赞

**【案例介绍】**

现有一个学生表s\_student和一个班级表c\_class，其中，班级表c\_class和学生表s\_student是一对多的关系。学生表s\_student和班级表c\_class如下所示。

<table style="width:500px;"> 
 <tbody> 
  <tr> 
   <td colspan="4" style="text-align:center;">学生表（s_student）</td> 
  </tr> 
  <tr> 
   <td style="text-align:center;">学生id（id）</td> 
   <td style="text-align:center;">学生姓名（name）</td> 
   <td style="text-align:center;">学生年龄（age）</td> 
   <td style="text-align:center;">所属班级（cid）</td> 
  </tr> 
  <tr> 
   <td style="text-align:center;">1</td> 
   <td style="text-align:center;">张三</td> 
   <td style="text-align:center;">18</td> 
   <td style="text-align:center;">1</td> 
  </tr> 
  <tr> 
   <td style="text-align:center;">2</td> 
   <td style="text-align:center;">李四</td> 
   <td style="text-align:center;">18</td> 
   <td style="text-align:center;">2</td> 
  </tr> 
  <tr> 
   <td style="text-align:center;">3</td> 
   <td style="text-align:center;">王五</td> 
   <td style="text-align:center;">19</td> 
   <td style="text-align:center;">2</td> 
  </tr> 
  <tr> 
   <td style="text-align:center;">4</td> 
   <td style="text-align:center;">赵六</td> 
   <td style="text-align:center;">20</td> 
   <td style="text-align:center;">1</td> 
  </tr> 
 </tbody> 
</table>

<table style="width:500px;"> 
 <tbody> 
  <tr> 
   <td colspan="2" style="text-align:center;">班级表（c_class）</td> 
  </tr> 
  <tr> 
   <td style="text-align:center;">班级id（id）</td> 
   <td style="text-align:center;">班级名称（classname）</td> 
  </tr> 
  <tr> 
   <td style="text-align:center;">1</td> 
   <td style="text-align:center;">一班</td> 
  </tr> 
  <tr> 
   <td style="text-align:center;">2</td> 
   <td style="text-align:center;">二班</td> 
  </tr> 
 </tbody> 
</table>

请使用MyBatis注解完成以下要求。

（1）MyBatis注解实现查询操作。

根据表格在数据库分别创建一个学生表s\_student和一个班级表c\_class，并查询id为2的学生的信息

（2）MyBatis注解实现修改操作。

将id为4的学生姓名修改为李雷，年龄修改为21。

（3）MyBatis注解实现一对多查询。

查询出二班所有学生的信息。

**【案例实现】**

![1accab995e6c41a3bda8c2c97b554b11.png][]

**1.数据准备：**在MySQL中创建一个名称为mybatis的数据库。

CREATE DATABASE mybatis;

①在数据库中创建班级表c\_class，并插入测试数据：

create table c_class (
      id int(32) primary key auto_increment,
      classname varchar(40)
     );

insert into c_class values (1, '一班');
    insert into c_class values (2, '二班');

②在数据库中创建学生表s\_student，并插入测试数据：

create table s_student (
      id int(32) primary key auto_increment,
      name varchar(40),
      age int,
      cid int(32) NOT NULL,
      foreign key(cid) references c_class(id)
     );

insert into s_student values (1, '张三', 18,1);
    insert into s_student values (2, '李四', 18,2);
    insert into s_student values (3, '王五', 19,2);
    insert into s_student values (4, '赵六', 20,1);

**2.引入相关依赖：**在项目的pom.xml文件中导入[MySQL驱动][MySQL]包、JUnit测试包、MyBatis的核心包等相关依赖。

<?xml version="1.0" encoding="UTF-8"?>
    <project xmlns="http://maven.apache.org/POM/4.0.0"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
        <modelVersion>4.0.0</modelVersion>
     
        <groupId>org.xinhua</groupId>
        <artifactId>MyBatisTest</artifactId>
        <version>1.0-SNAPSHOT</version>
     
        <properties>
            <maven.compiler.source>17</maven.compiler.source>
            <maven.compiler.target>17</maven.compiler.target>
            <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        </properties>
     
        <dependencies>
            <dependency>
                <groupId>org.mybatis</groupId>
                <artifactId>mybatis</artifactId>
                <version>3.5.11</version>
            </dependency>
            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
                <version>8.0.28</version>
            </dependency>
            <dependency>
                <groupId>junit</groupId>
                <artifactId>junit</artifactId>
                <version>4.12</version>
                <scope>compile</scope>
            </dependency>
        </dependencies>
        <build>
            <resources>
                <resource>
                    <directory>src/main/java</directory>
                    <includes>
                        <include>**/*.properties</include>
                        <include>**/*.xml</include>
                    </includes>
                    <filtering>true</filtering>
                </resource>
            </resources>
        </build>
     
    </project>

**3.POJO类准备：①**创建持久化类IStudent，并在类中定义相关属性和方法，该类用于封装IStudent对象的id、姓名、年龄和班级等属性。

package com.itheima.pojo;
    
    public class IStudent {
        private Integer id; //主键id
        private String name; //姓名
        private int age; //年龄
        private int cid; //班级
    
        public Integer getId() {
            return id;
        }
    
        public void setId(Integer id) {
            this.id = id;
        }
    
        public String getName() {
            return name;
        }
    
        public void setName(String name) {
            this.name = name;
        }
    
        public int getAge() {
            return age;
        }
    
        public void setAge(int age) {
            this.age = age;
        }
    
        public int getCid() {
            return cid;
        }
    
        public void setCid(int cid) {
            this.cid = cid;
        }
    
        @Override
        public String toString() {
            return "Student{" + "id=" + id + ",name=" + name + ",age=" + age + '}';
        }
    }

**②**创建持久化类IClass，并在类中定义相关属性和方法，该类用于封装IClass对象的id、班级名称以及关联的学生集合等属性。

package com.itheima.pojo;
    import java.util.List;
    
    public class IClass {
        private Integer id; //主键id
        private String classname; //班级名称
        private List<IStudent> studentList; //学生集合
    
        public Integer getId() {
            return id;
        }
    
        public void setId(Integer id) {
            this.id = id;
        }
    
        public String getClassname() {
            return classname;
        }
    
        public void setClassname(String classname) {
            this.classname = classname;
        }
    
        public List<IStudent> getStudentList() {
            return studentList;
        }
    
        public void setStudentList(List<IStudent> studentList) {
            this.studentList = studentList;
        }
    
        @Override
        public String toString() {
            return "IClass{" + "id=" + id + ",classname=" + classname +  ",studentList=" + studentList + '}';
        }
    }

**4.创建Mapper接口：**①创建IStudentMapper接口，用于编写@Select注解映射的select查询语句、@Update注解映射update更新语句等。

package com.itheima.dao;
    
    import java.util.List;
    import com.itheima.pojo.IStudent;
    import org.apache.ibatis.annotations.Result;
    import org.apache.ibatis.annotations.Results;
    import org.apache.ibatis.annotations.Select;
    import org.apache.ibatis.annotations.Update;
    
    public interface IStudentMapper {
        //MyBatis注解实现查询操作
        @Select("select * from s_student where id = #{id}")
        IStudent selectStudent(int id);
    
        //MyBatis注解实现修改操作
        @Update("update mybatis.s_student set name=#{name},age=#{age} where id=#{id}")
        int updateStudent(IStudent student);
    
        //MyBatis注解实现一对多查询
        @Select("select * from s_student where cid = #{id}")
        @Results({@Result(id = true,column = "id",property = "id"),
                @Result(column = "classname",property = "classname")
        })
        List<IStudent> selectStudentByCid(int cid); //通过cid查询对应班级中的学生信息
    }

②创建IClassMapper接口，在接口中编写selectClassById()方法，通过id查询班级信息。

package com.itheima.dao;
    
    import com.itheima.pojo.IClass;
    import org.apache.ibatis.annotations.Many;
    import org.apache.ibatis.annotations.Result;
    import org.apache.ibatis.annotations.Results;
    import org.apache.ibatis.annotations.Select;
    
    public interface IClassMapper {
        @Select("select * from c_class where id=#{id} ")
        @Results({@Result(id = true, column = "id", property = "id"),
                @Result(column = "classname", property = "classname"),
                @Result(column = "id", property = "studentList",
                        many = @Many(select = "com.itheima.dao.IStudentMapper.selectStudentByCid"))})
        IClass selectClassById(int id);
    }

**5.创建数据库连接信息配置文件db.properties：**在该文件中配置数据库连接的参数。

mysql.driver=com.mysql.cj.jdbc.Driver
    mysql.url=jdbc:mysql://localhost:3306/mybatis?serverTimezone=UTC&\
      characterEncoding=utf8&useUnicode=true&useSSL=false
    mysql.username=root
    mysql.password=root

**6.创建MyBatis的核心配置文件mybatis-config.xml：**该文件主要用于项目的环境配置。

<?xml version="1.0" encoding="UTF-8" ?>
    <!DOCTYPE configuration
            PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
            "http://mybatis.org/dtd/mybatis-3-config.dtd">
    <configuration>
        
        
        <properties resource="db.properties"/>
        <environments default="development">
            <environment id="development">
                <transactionManager type="JDBC"/>
                
                <dataSource type="POOLED">
                    <property name="driver" value="${mysql.driver}"/>
                    <property name="url" value="${mysql.url}"/>
                    <property name="username" value="${mysql.username}"/>
                    <property name="password" value="${mysql.password}"/>
                </dataSource>
            </environment>
        </environments>
    
        
        <mappers>
            <mapper class="com.itheima.dao.IStudentMapper"/>
            <mapper class="com.itheima.dao.IClassMapper"/>
        </mappers>
    
    </configuration>

**7.编写mybatisUtils工具类：**该类用于封装读取配置文件信息的代码。

package com.itheima.Utils;
     
    import java.io.Reader;
    import org.apache.ibatis.io.Resources;
    import org.apache.ibatis.session.SqlSession;
    import org.apache.ibatis.session.SqlSessionFactory;
    import org.apache.ibatis.session.SqlSessionFactoryBuilder;
     
    public class MyBatisUtils {
        private static SqlSessionFactory sqlSessionFactory = null;
        //初始化SQLSessionFactory类加载MyBatis的配置文件
        static {
            try {
                //使用MyBatis提供的Resources类加载MyBatis的配置文件
                Reader reader = Resources.getResourceAsReader("mybatis-config.xml");
                //构建SqlSessionFactory工厂
                sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
            }catch(Exception e){
                e.printStackTrace();
            }
        }
        public static SqlSession getSession(){
            //获取SqlSession对象的静态方法
            return sqlSessionFactory.openSession(true);
            //若传入true表示关闭事务控制，自动提交;false表示开启事务控制
        }
    }

**8.编写测试方法：**在测试类MyBatisTest中，编写测试方法。

package Test;
    import com.itheima.Utils.MyBatisUtils;
    import com.itheima.dao.IClassMapper;
    import com.itheima.dao.IStudentMapper;
    import com.itheima.pojo.IClass;
    import com.itheima.pojo.IStudent;
    import org.apache.ibatis.session.SqlSession;
    import org.junit.Test;
    
    public class MyBatisTest {
        //(1)MyBatis注解实现查询操作
        @Test
        public void findStudentByTest(){
            //1.通过工具类获取SqlSession对象
            SqlSession session = MyBatisUtils.getSession();
            IStudentMapper mapper = session.getMapper(IStudentMapper.class);
            //2.使用IStudentMapper对象查询id为1的学生的信息
            IStudent student = mapper.selectStudent(2);
            System.out.println(student.toString());
            //3.关闭SqlSession
            session.close();
        }
    
        //(2)MyBatis注解实现修改操作
        @Test
        public void updateIStudentTest(){
            SqlSession session = MyBatisUtils.getSession();
            IStudent student = new IStudent();
            student.setId(4);
            student.setName("李雷");
            student.setAge(21);
            IStudentMapper mapper = session.getMapper(IStudentMapper.class);
            int result = mapper.updateStudent(student);
            if(result>0){
                System.out.println("更新成功"+result+"条数据");
            }
            else {
                System.out.println("更新数据失败");
            }
            System.out.println(student.toString());
            session.commit();
            //关闭SqlSession
            session.close();
        }
    
        //(3)MyBatis注解实现一对多查询
        @Test
        public void selectClassByIdTest() {
            // 1.通过工具类生成SqlSession对象
            SqlSession session = MyBatisUtils.getSession();
            IClassMapper mapper = session.getMapper(IClassMapper.class);
            // 2.查询id为2的班级中学生的信息
            IClass icalss = mapper.selectClassById(2);
            System.out.println(icalss.toString());
            session.close();
        }
    }

**9.运行结果：**

![27a22d388a804e9091f6ac8f0af11959.png][] ![c4f61f8e18b14162825f487e0e64b9de.png][] ![8134ba03eaff459688a3cce559e7b3c1.png][]

[1accab995e6c41a3bda8c2c97b554b11.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/25/64e70cf97f7041f999fc2150847c018b.png
[MySQL]: https://so.csdn.net/so/search?q=MySQL%E9%A9%B1%E5%8A%A8&spm=1001.2101.3001.7020
[27a22d388a804e9091f6ac8f0af11959.png]: https://img-blog.csdnimg.cn/27a22d388a804e9091f6ac8f0af11959.png
[c4f61f8e18b14162825f487e0e64b9de.png]: https://img-blog.csdnimg.cn/c4f61f8e18b14162825f487e0e64b9de.png
[8134ba03eaff459688a3cce559e7b3c1.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/25/f6c32baa2de54dc4ab8efd590db0a107.png