MyBatis快速入门

MyBatis快速入门

一、简介

MyBatis是一款优秀的持久层框架;JavaEE的三层架构;表现层、业务层、持久层;;用于简化JDBC开发;原始JDBC开发的缺点;硬编码、操作繁琐;;官网链接为; link.本文将以最简单易懂的方式教你快速创建MyBatis项目。

二、快速入门

写MyBatis之前分为三步操作;
1.导入坐标;
2.编写MyBatis核心配置文件;
3.编写SQL映射文件。
下面逐一介绍;

1.导入坐标

打开pom.xml文件;暂时先加入以下依赖;;如果以后做项目还需要其它的;可另行加入;

<?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>

<!--    当前项目的坐标-->
    <groupId>org.example</groupId>
    <artifactId>maven-project</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

<!--    导入mysql的驱动jar包-->
    <dependencies>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.46</version>
        </dependency>
        <dependency>
<!--            mybatis需要的坐标-->
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.5</version>
        </dependency>
<!--        导入junit单元测试框架-->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.13</version>
            <scope>test</scope>
        </dependency>
<!--        添加slf4j日志api-->
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-api</artifactId>
            <version>1.7.20</version>
        </dependency>
<!--        添加logback-classic依赖-->
        <dependency>
            <groupId>ch.QOS.logback</groupId>
            <artifactId>logback-classic</artifactId>
            <version>1.2.3</version>
        </dependency>
<!--        添加logback-core依赖-->
        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-core</artifactId>
            <version>1.2.3</version>
        </dependency>
    </dependencies>
</project>

<?xml version=;1.0; encoding=;UTF-8; ?>
<!DOCTYPE configuration
        PUBLIC ;-//mybatis.org//DTD Config 3.0//EN;
        ;https://mybatis.org/dtd/mybatis-3-config.dtd;>
<configuration>
    <environments default=;development;>
        <environment id=;development;>
            <transactionManager type=;JDBC;/>
            <dataSource type=;POOLED;>
<!--                数据库连接信息-->
                <property name=;driver; value=;com.mysql.jdbc.Driver;/>
                <property name=;url; value=;jdbc:mysql:///mybatis?useSSL=false;/>
                <property name=;username; value=;root;/>
                <property name=;password; value=;ZWQQq123qwe;/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
    <!--加载sql的映射文件-->
    <!--Mapper代理方式;因为以后如果有很多SQL映射文件;我们就不用写很多行了;直接以下一行采用包扫描方式解决-->
        <package name=;com.mapper;/>
    </mappers>
</configuration>

<?xml version=;1.0; encoding=;UTF-8; ?>
<!DOCTYPE mapper
        PUBLIC ;-//mybatis.org//DTD Mapper 3.0//EN;
        ;https://mybatis.org/dtd/mybatis-3-mapper.dtd;>
<mapper namespace=;com.mapper.UserMapper;>
<!--    设置返回值类型为我们自定义的类User-->
    <select id=;selectAll; resultType=;com.zhou.User;>
        select * from tb_user
    </select>
</mapper>

package com.mapper;

import com.zhou.User;

import java.util.List;

public interface UserMapper {
    List<User> selectAll();
}

<?xml version=;1.0; encoding=;UTF-8; ?>
<!DOCTYPE mapper
        PUBLIC ;-//mybatis.org//DTD Mapper 3.0//EN;
        ;https://mybatis.org/dtd/mybatis-3-mapper.dtd;>
<mapper namespace=;com.mapper.UserMapper;>
<!--    设置返回值类型为我们自定义的类User-->
    <select id=;selectAll; resultType=;com.zhou.User;>
        select * from tb_user
    </select>
</mapper>

package com.mapper;

import com.zhou.User;

import java.util.List;

public interface UserMapper {
    List<User> selectAll();
}

package com.zhou;

import com.mapper.UserMapper;
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.InputStream;
import java.util.List;

public class MyBatisDemo2 {
    public static void main(String[] args) throws Exception{
        //1.加载MyBatis核心配置文件;获取sqlSessionFactory
        String resource = ;mybatis-config.xml;;
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

        //2.获取sqlSession对象;用它执行sql
        SqlSession sqlSession=sqlSessionFactory.openSession();
        UserMapper userMapper=sqlSession.getMapper(UserMapper.class);

        //3.执行sql
        List<User> users=userMapper.selectAll();
        System.out.println(users);

        //4.释放资源
        sqlSession.close();
    }
}