[Java知识库]Mybatis 快速入门

创建maven工程

准备数据

CREATE DATABASE /*!32312 IF NOT EXISTS*/`mybatis_db` /*!40100 DEFAULT CHARACTER SET utf8 */;
USE `mybatis_db`;
DROP TABLE IF EXISTS `user`;
CREATE TABLE `user` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `username` varchar(50) DEFAULT NULL,
  `password` varchar(50) DEFAULT NULL,
  `age` int(3) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8;
insert  into `user`(`id`,`username`,`age`,`age`) values (1,'UZI','1234',19),(2,'PDD','123',25);

导入依赖

 <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.7</version>
        </dependency>
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.22</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.13</version>
        </dependency>
        <!--mysql驱动-->

创建数据库的信息文件properties

jdbc.url=jdbc:mysql://localhost:3306/mybatis?useUnicode=true&characterEncoding=utf-8&useSSL=false&serverTimezone = GMT
jdbc.driver=com.mysql.jdbc.Driver
jdbc.username=root
jdbc.password=317311

创建mybatis的配置文件

<?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>
    <!--设置配置文件所在的路径-->
    <properties resource="jdbc.properties"/>
    <!-- 默认使用的数据库-->
    <environments default="development">
    		<!-- 这个标签可以多个 environment 代表多个不同的数据库 -->
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <!--获取配置文件中配置的对应的值来设置连接相关参数-->
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.username}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
    </environments>
    <!-- mapper  xml文件映射的地方-->
  <!-- 定义dao接口所在的包。要求xml文件存放的路径和dao接口的包名要对应 -->
    <mappers>
        <package name="com.hgzy.dao"/>
    </mappers>
</configuration>

实体类 位置： com.hgzy.pojo
因为我这加入了lombok依赖 注解生成setget方法

package com.hgzy.pojo;

import lombok.Data;
import lombok.ToString;

@Data
@ToString
public class User {
    private Integer id ;
    private String user;
    private String pwd;
    private Integer age ;
}

dao 层 位置：com.hgzy.dao

package com.hgzy.dao;

import com.hgzy.pojo.User;

public interface UserDao {
    User findUserById(Integer id);
}

dao 层xml文件及 位置：com.hgzy.dao

<?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.hgzy.dao.UserDao">

    <select id="findUserById" resultType="com.hgzy.pojo.User">
        select * from user where id=#{id}
    </select>
</mapper>

调试方法

 public static void main(String[] args) throws IOException {
        //定义mybatis配置文件的路径
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        //获取Sqlsession对象
        SqlSession sqlSession = sqlSessionFactory.openSession();
        //获取UserDao实现类对象
        UserDao userDao = sqlSession.getMapper(UserDao.class);
        //调用方法测试
        List<User> userList = userDao.findAll();
        System.out.println(userList);
        //释放资源
        sqlSession.close();
    }