Hello MyBatis !

 导入依赖

<?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>4.0.0modelVersion>

    <groupId>org.examplegroupId>
    <artifactId>Mybatis_StudyartifactId>
    <packaging>pompackaging>
    <version>1.0-SNAPSHOTversion>
    <modules>
        <module>mybatis_01module>
    modules>

    <properties>
        <maven.compiler.source>8maven.compiler.source>
        <maven.compiler.target>8maven.compiler.target>
    properties>

    <dependencies>
        
        <dependency>
            <groupId>org.mybatisgroupId>
            <artifactId>mybatisartifactId>
            <version>3.5.3version>
        dependency>

        <dependency>
            <groupId>junitgroupId>
            <artifactId>junitartifactId>
            <version>4.12version>
            <scope>testscope>
        dependency>

        <dependency>
            <groupId>mysqlgroupId>
            <artifactId>mysql-connector-javaartifactId>
            <version>5.1.47version>
        dependency>



    dependencies>


project>

配置环境(设置与数据库连接的一些条件)

<?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="development">

        <environment id="development">

            <transactionManager type="JDBC"/>

            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis?useSSL=false&useUnicode=true&characterEncoding=UTF-8"/>
                <property name="username" value="root"/>
                <property name="password" value="my7shig69l>A"/>
            dataSource>
        environment>
    environments>

    <mappers>
        <mapper resource="com/ljm/dao/UserMapper.xml"/>
    mappers>

configuration>

编写工具类(获取SqlSession对象,用来实现对数据库的操作)

import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class UserDao_test {
    @Test
    public void test(){
        //获得SqlSession对象
        SqlSession sqlSession=MybatisUtils.getSqlSession();
        //执行sql
        UserDao mapper=sqlSession.getMapper(UserDao.class);
        //com.ljm.dao.UserDao 需要去配置
        List<User> userList = mapper.getUserList();

        for(User user:userList){
            System.out.println(user);
        }

        sqlSession.close();
    }
}

接口(公有操作,这里用来获取用户信息)

 用户类(的字段与数据库的对象字段相同?)

 Mapper.xml  (实现接口,取代以前的*lmp实现类)

<?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.ljm.dao.UserDao">



    <select id="getUserList" resultType="com.ljm.pojo.User">
        select * from mybatis.user
    select>


mapper>

测试

import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class UserDao_test {
    @Test
    public void test(){
        //获得SqlSession对象
        SqlSession sqlSession=MybatisUtils.getSqlSession();
        //获取用来执行sql的mapper

//        获取方式一(推荐):
        UserDao mapper=sqlSession.getMapper(UserDao.class);
        //com.ljm.dao.UserDao 需要去配置
//        List userList = mapper.getUserList();

//        方式二
        List userList=sqlSession.selectList("com.ljm.dao.UserDao.getUserList");

        for(User user:userList){
            System.out.println(user);
        }

        sqlSession.close();
    }
}

 官方建议(为了确保每次都能执行关闭操作，你应该把这个关闭操作放到 finally 块中)

import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class UserDao_test {
    @Test
    public void test(){
        //获得SqlSession对象
        SqlSession sqlSession = null;
        //获取用来执行sql的mapper
        try {
            sqlSession=MybatisUtils.getSqlSession();
            //        获取方式一(推荐):
            UserDao mapper=sqlSession.getMapper(UserDao.class);
            List userList = mapper.getUserList();

//        方式二
//            List userList=sqlSession.selectList("com.ljm.dao.UserDao.getUserList");
            for(User user:userList){
                System.out.println(user);
            }
        } finally {
            sqlSession.close();
        }
    }
}

可能遇到的问题

 解决方法  pom.xml中添加

 <build>
        <resources>
            <resource>
                <directory>src/main/resourcesdirectory>
                <includes>
                    <include>**/*.propertiesinclude>
                    <include>**/*.xmlinclude>
                includes>
            resource>
            <resource>
                <directory>src/main/javadirectory>
                <includes>
                    <include>**/*.propertiesinclude>
                    <include>**/*.xmlinclude>
                includes>
            resource>
        resources>
    build>