Mybatis学习demo01-入门案例

桃扇骨 2022-11-28 00:45 136阅读 0赞

## 1、什么是 MyBatis？ ##

MyBatis 是一款优秀的持久层框架，它支持自定义 SQL、存储过程以及高级映射。MyBatis 免除了几乎所有的 JDBC 代码以及设置参数和获取结果集的工作。MyBatis 可以通过简单的 XML 或注解来配置和映射原始类型、接口和 Java POJO（Plain Old Java Objects，普通老式 Java 对象）为数据库中的记录。

中文文档参考：[https://mybatis.org/mybatis-3/zh/getting-started.html][https_mybatis.org_mybatis-3_zh_getting-started.html]

## 2、Mybatis 的环境搭建 ##

*  创建maven项目，导入相关依赖

<?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>com.wan.mybatis</groupId>
        <artifactId>day01_mybatis</artifactId>
        <version>1.0-SNAPSHOT</version>
    
        <packaging>jar</packaging>
        
        <dependencies>
            
            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
                <version>5.1.47</version>
            </dependency>
            
            
            <dependency>
                <groupId>org.mybatis</groupId>
                <artifactId>mybatis</artifactId>
                <version>3.5.2</version>
            </dependency>
            
            <dependency>
                <groupId>junit</groupId>
                <artifactId>junit</artifactId>
                <version>4.12</version>
            </dependency>
            
            <dependency>
                <groupId>log4j</groupId>
                <artifactId>log4j</artifactId>
                <version>1.2.17</version>
            </dependency>
    
        </dependencies>
    
    
    </project>

*  创建数据库和表

-- 创建数据库
    create database if not exists db_mybatis character set utf8;
    -- 创建数据表
    drop table if exists `user`;
    create table `user` (
      `id` int(11) not null auto_increment,
      `username` varchar(32) not null comment '用户名称',
      `birthday` datetime default null comment '生日',
      `sex` char(1) default null comment '性别',
      `address` varchar(256) default null comment '地址',
      primary key  (`id`)
    ) engine=innodb default charset=utf8;
    -- 添加记录
    insert  into `user`(`id`,`username`,`birthday`,`sex`,`address`) 
    values (17,'wan1','2000-02-27 17:47:08','男','湖北武汉'),
    (18,'wan2','2000-03-02 15:09:37','女','云南昆明'),
    (19,'wan3','2001-03-04 11:34:34','女','广西贵港'),
    (20,'wan4','2002-03-04 12:04:06','男','湖北恩施'),
    (21,'wan5','1999-03-07 17:37:26','男','云南文山'),
    (22,'wan6','1998-03-08 11:44:00','女','湖南长沙');

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*  创建实体类（实体类属性名与数据库表字段名保持一致）

package com.wan.mybatis;
    
    
    import com.mysql.fabric.xmlrpc.base.Data;
    
    import java.io.Serializable;
    
    public class User implements Serializable {
        
        private Integer id;
        private String username;
        private Data birthday;
        private String sex;
        private String address;
    
        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 Data getBirthday() {
        
            return birthday;
        }
    
        public void setBirthday(Data birthday) {
        
            this.birthday = birthday;
        }
    
        public String getSex() {
        
            return sex;
        }
    
        public void setSex(String sex) {
        
            this.sex = sex;
        }
    
        public String getAddress() {
        
            return address;
        }
    
        public void setAddress(String address) {
        
            this.address = address;
        }
    
        @Override
        public String toString() {
        
            return "User{" +
                    "id=" + id +
                    ", username='" + username + '\'' +
                    ", birthday=" + birthday +
                    ", sex='" + sex + '\'' +
                    ", address='" + address + '\'' +
                    '}';
        }
    }

*  创建实体类的持久层接口（mapper 或 dao）

package com.wan.dao;
    
    import com.wan.mybatis.User;
    import org.apache.ibatis.annotations.Select;
    
    import java.util.List;
    
    public interface IUserDao {
        
    //    查询所有操作
        List<User> findAll();
    }

*  编写接口映射文件IUserDao.xml（官方推荐UserMapper.xml）

<?xml version="1.0" encoding="UTF-8" ?>
    <!DOCTYPE mapper
            PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
            "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
    
    
    <mapper namespace="com.wan.dao.IUserDao">
    
       
    <select id="findAll" resultType="com.wan.mybatis.User">
        select *from user;
    </select>
    </mapper>

*  编写 Mybatis 的主配置文件（官方推荐mybatis-config.xml）

<?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>
      <environments default="development">
        <environment id="development">
          <transactionManager type="JDBC"/>
          <dataSource type="POOLED">
            <property name="driver" value="${driver}"/>
            <property name="url" value="${url}"/>
            <property name="username" value="${username}"/>
            <property name="password" value="${password}"/>
          </dataSource>
        </environment>
      </environments>
      <mappers>
        <mapper resource="org/mybatis/example/BlogMapper.xml"/>
      </mappers>
    </configuration>

我的主配置文件

<?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>
    
        <environments default="mysql">
    
            <environment id="mysql">
    
                <transactionManager type="JDBC"/>
    
                <dataSource type="POOLED">
    
                    <property name="driver" value="com.mysql.jdbc.Driver"/>
                    <property name="url" value="jdbc:mysql://localhost:3306/数据库名称?useSSL=true&useUnicode=true&characterEncoding=UTF-8"/>
                    <property name="username" value="root"/>
                    <property name="password" value="******"/>
                </dataSource>
            </environment>
        </environments>
    
    
        <mappers>
            <mapper resource="com/wan/dao/IUserDao.xml"/>
        </mappers>
    </configuration>

## 3、编写入门案例-测试类 ##

package com.wan.test;
    
    import com.wan.dao.IUserDao;
    import com.wan.mybatis.User;
    import org.apache.ibatis.io.Resources;
    import org.apache.ibatis.session.SqlSession;
    import org.apache.ibatis.session.SqlSessionFactory;
    import org.apache.ibatis.session.SqlSessionFactoryBuilder;
    
    import java.io.IOException;
    import java.io.InputStream;
    import java.util.List;
    
    public class MybatisTest {
        
    //    入门案例
        public static void main(String[] args) throws IOException {
        
        //  1.读取配置文件
            InputStream in = Resources.getResourceAsStream("SqlMapConfig.xml");
            //  2.从 XML 中构建 SqlSessionFactory
            SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
            SqlSessionFactory factory = builder.build(in);
            //  3. 从 SqlSessionFactory 中获取 SqlSession
            SqlSession session = factory.openSession();
            //  4.使用 SqlSession 创建Dao接口的代理对象
            IUserDao userDao = session.getMapper(IUserDao.class);
            //  5.使用代理对象执行方法
            List<User> users = userDao.findAll();
            for (User user : users) {
        
                System.out.println(user);
    
            }
            //  6.释放资源
            session.close();
            in.close();
    
        }
    }

## 4、测试案例代码解析 ##

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## 5、执行查询所有、创建代理对象的分析 ##

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## 5、常见问题以及总览图链接 ##

Mybatis学习常见问题以及解决方法01  
[https://blog.csdn.net/weixin\_46047285/article/details/108036469][https_blog.csdn.net_weixin_46047285_article_details_108036469]

[https_mybatis.org_mybatis-3_zh_getting-started.html]: https://mybatis.org/mybatis-3/zh/getting-started.html
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[https_blog.csdn.net_weixin_46047285_article_details_108036469]: https://blog.csdn.net/weixin_46047285/article/details/108036469