MyBatis学习笔记（二）：快速入门实例

亦凉 2022-05-12 12:04 217阅读 0赞

###  MyBatis学习笔记（二）：快速入门实例 ###

1. 开发环境准备

2. 相关类及配置文件准备

3. 测试代码准备

--------------------

在上一篇文章中，笔者已经介绍了MyBatis的架构和运作流程，本篇文章将结合一个完整的实例介绍MyBatis的用法。

### 1. 开发环境准备 ###

1. 创建一个测试用的maven工程，当然，Java工程或者JavaWeb工程也是可以的。如下所示：

![70][]

2. 在maven工程的pom文件中添加响应的依赖：

<dependency>
    	<groupId>org.mybatis</groupId>
    	<artifactId>mybatis</artifactId>
    	<version>3.4.6</version>
    </dependency>
    <dependency>
    	<groupId>mysql</groupId>
    	<artifactId>mysql-connector-java</artifactId>
    	<version>6.0.6</version>
    </dependency>

3. 启动MySql数据库，并创建一个表：t\_user

create table t_user(
        id int primary key auto_increment,
        username varchar(20),
        password varchar(20),
        account decimal(10,2)
        );

--------------------

### 2. 相关类及配置文件准备 ###

1. 创建一个与数据表 t\_user 对应的Java Bean：UserBean

package com.yingshulan.mybatis.mybatis_learning;
    
    import java.io.Serializable;
    
    public class UserBean implements Serializable
    {
    
        private static final long serialVersionUID = 1L;
        private Integer id;
        private String username;
        private String password;
        private Double account;
    
        public UserBean()
        {
            super();
        }
    
        public UserBean(String username, String password, Double account)
        {
            super();
            this.username = username;
            this.password = password;
            this.account = account;
        }
    
        public UserBean(Integer id, String username, String password, Double account)
        {
            super();
            this.id = id;
            this.username = username;
            this.password = password;
            this.account = account;
        }
    
        public Integer getId()
        {
            return id;
        }
    
        public void setId(Integer id)
        {
            this.id = id;
        }
    
        public String getUsername()
        {
            return username;
        }
    
        public void setUsername(String username)
        {
            this.username = username;
        }
    
        public String getPassword()
        {
            return password;
        }
    
        public void setPassword(String password)
        {
            this.password = password;
        }
    
        public Double getAccount()
        {
            return account;
        }
    
        public void setAccount(Double account)
        {
            this.account = account;
        }
    
        @Override
        public String toString()
        {
            return "UserBean [id=" + id + ", username=" + username + ", password=" + password
                    + ", account=" + account + "]";
        }
    
    }

2. 为UserBean创建对应的增、删、改、查接口类：UserMapper.java，代码如下：

package com.yingshulan.mybatis.mybatis_learning;
    
    import java.util.List;
    
    public interface UserMapper
    {
        /**
         * 新增用戶
         * @param user
         * @return
         * @throws Exception
         */
        public int insertUser(UserBean user) throws Exception;
    
        /**
         * 修改用戶
         * @param user
         * @param id
         * @return
         * @throws Exception
         */
        public int updateUser(UserBean user, int id) throws Exception;
    
        /**
         * 刪除用戶
         * @param id
         * @return
         * @throws Exception
         */
        public int deleteUser(int id) throws Exception;
    
        /**
         * 根据id查询用户信息
         * @param id
         * @return
         * @throws Exception
         */
        public UserBean selectUserById(int id) throws Exception;
    
        /**
         * 查询所有的用户信息
         * @return
         * @throws Exception
         */
        public List<UserBean> selectAllUser() throws Exception;
    }

3. 接口类中的方法要与实际的SQL语句对应起来，需要一个映射配置文件：UserMapper.xml，如下所示：

<?xml version="1.0" encoding="UTF-8"?>
    <!DOCTYPE mapper PUBLIC "-//mybatis.org/DTD Mapper 3.0" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
    <mapper namespace="com.yingshulan.mybatis.mybatis_learning.UserMapper">
    
       <resultMap id="userMap" type="UserBean">
            <id property="id" column="id" javaType="java.lang.Integer"></id>
            <result property="username" column="username" javaType="java.lang.String"></result>
            <result property="password" column="password" javaType="java.lang.String"></result>
            <result property="account" column="account" javaType="java.lang.Double"></result>
        </resultMap>
        
        
    
    
    
    
        <insert id="insertUser" useGeneratedKeys="true" keyProperty="id">
            insert into t_user (username,password,account) values (#{username},#{password},#{account})
        </insert>
        
        <update id="updateUser" >
          update t_user set username=#{username},password=#{password},account=#{account} where id=#{id}
        </update>
        
        <delete id="deleteUser" parameterType="int">
         delete from t_user where id=#{id}  
        </delete>
        
        <select id="selectUserById" parameterType="int" resultMap="userMap">
         select * from t_user where id=#{id}
        </select>
        
        <select id="selectAllUser" resultMap="userMap">
         select * from t_user
        </select>  
        
    </mapper>

4. MyBatis配置文件，每个MyBatis应用程序主要都是使用SqlSessionFactory实例的，一个SqlSessionFactory实例可以通过SqlSessionFactoryBuilder获得。SqlSessionFactoryBuilder可以从一个xml配置文件或者一个预定义的配置类的实例获得。本例中采用的是xml配置文件，命名为：mybatis.cfg.xml，如下所示：

<?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>
       
       <typeAliases >
            
            
            <package name="com.yingshulan.mybatis.mybatis_learning"/>
       </typeAliases>
       
       
       
         <environments default="cybatis">
            <environment id="cybatis">
                
                <transactionManager type="JDBC" />
                
                
                
                
                
                <dataSource type="POOLED">
                    <property name="driver" value="com.mysql.jdbc.Driver" />
                    <property name="url" value="jdbc:mysql://localhost:3306/mysql?useUnicode=true&serverTimezone=UTC" />
                    <property name="username" value="root" />
                    <property name="password" value="123456" />
                </dataSource>
            </environment>
        </environments> 
        
        <mappers>
            
            
            <package name="com/yingshulan/mybatis/mybatis_learning"/>
        </mappers>
    </configuration>

--------------------

### 3. 测试代码准备 ###

为了验证完整的流程，需创建一个测试类：UserService.java

package com.yingshulan.mybatis.mybatis_learning;
    
    import java.io.Reader;
    import java.util.List;
    
    import org.apache.ibatis.io.Resources;
    import org.apache.ibatis.session.SqlSession;
    import org.apache.ibatis.session.SqlSessionFactoryBuilder;
    
    public class UserService
    {
        public static SqlSession session;
        
        public static void main(String[] args)
        {
            try
            {
                //使用MyBatis提供的Resources类加载mybatis的配置文件
                Reader reader = Resources.getResourceAsReader("mybatis.cfg.xml");
                //构建sqlSession的工厂 ,并开启 SqlSession     
                session = new SqlSessionFactoryBuilder().build(reader).openSession();
            }
            catch (Exception e)
            {
                e.printStackTrace();
            }
            
            insertUser();      
            // deleteUser();
            selectUserById();
            selectAllUser();
        }
    
        /**
         * 新增用户
         */
        private static void insertUser()
        {
            System.out.println("****************Insert User********************");
            UserMapper mapper = session.getMapper(UserMapper.class);
            UserBean user = new UserBean("zhuliu", "123adfg9", 34567.0);
            try
            {
                mapper.insertUser(user);
                System.out.println(user.toString());
                session.commit();
            }
            catch (Exception e)
            {
                e.printStackTrace();
                session.rollback();
            }
        }
    
        /**
         * 删除用户
         */
        private static void deleteUser()
        {
            System.out.println("****************Delete User********************");
            UserMapper mapper = session.getMapper(UserMapper.class);
            try
            {
                mapper.deleteUser(1);
                session.commit();
            }
            catch (Exception e)
            {
                e.printStackTrace();
                session.rollback();
            }
        }
    
        /**
         * 根据id查询用户
         */
        private static void selectUserById()
        {
            System.out.println("****************Select User By ID********************");
            UserMapper mapper = session.getMapper(UserMapper.class);
            try
            {
                UserBean user = mapper.selectUserById(1);
                System.out.println(user.toString());
    
                session.commit();
            }
            catch (Exception e)
            {
                e.printStackTrace();
                session.rollback();
            }
        }
    
        /**
         * 查询所有的用户
         */
        private static void selectAllUser()
        {
            System.out.println("****************Select All User********************");
            UserMapper mapper = session.getMapper(UserMapper.class);
            try
            {
                List<UserBean> userList = mapper.selectAllUser();
                for (UserBean user : userList)
                {
                    System.out.println(user.toString());
                }        
                session.commit();
            }
            catch (Exception e)
            {
                e.printStackTrace();
                session.rollback();
            }
        }
    
    }

插入四条记录后的运行结果：

UserBean [id=4, username=zhuliu, password=123adfg9, account=34567.0]
    ****************Select User By ID********************
    UserBean [id=1, username=zhangsan, password=abcd1234, account=1234.0]
    ****************Select All User********************
    UserBean [id=1, username=zhangsan, password=abcd1234, account=1234.0]
    UserBean [id=2, username=lisi, password=123456789, account=13456.0]
    UserBean [id=3, username=wangwu, password=123adfg9, account=34567.0]
    UserBean [id=4, username=zhuliu, password=123adfg9, account=34567.0]

查询数据库 t\_user：

![70 1][]

**参考文献：**

1. 博客：[MyBatis学习笔记(一）入门][MyBatis] [https://www.cnblogs.com/hellokitty1/p/5216025.html][MyBatis]

[70]: /images/20220512/be3d8bd469f5478788beb0573668e2c8.png
[70 1]: /images/20220512/3ad426ba7788499081176800adbb3a4b.png
[MyBatis]: https://www.cnblogs.com/hellokitty1/p/5216025.html