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>
    <!--引入外部db.properties-->
    <properties resource="db.properties">
        <!--启动默认值属性-->
        <!--
        <property name="org.apache.ibatis.parsing.PropertyParser.enable-default-value" value="true"/>
        -->
        <!--如果在属性名中使用了 ":" 字符（如：db:username），或者在 SQL 映射中使用了 OGNL 表达式的三元运算符
        （如： ${tableName != null ? tableName : 'global_constants'}），就需要设置特定的属性来修改分隔属性名和默认值的字符。例如： -->
        <!--修改默认值的分隔符
        <property name="org.apache.ibatis.parsing.PropertyParser.default-value-separator" value="?:"/>
        -->
    </properties>

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

mapper.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为映射的根节点-->
<!--mapper为映射的根节点，namespace指定Dao接口的完整类名
mybatis会依据这个接口动态创建一个实现类去实现这个结构，
而这个实现类是一个Mapper对象-->
<mapper namespace="org.itheima.pojo.UserMapper">
    <!--id = “接口中的方法名”
    parameterType = “传入的参数类型”
    resultType = “返回实体类对象，使用包.类名”-->
    <select id="findById" parameterType="int"
            resultType="org.itheima.pojo.User">
        select * from users where id = #{id}
    </select>

    <!--对象中的属性可以直接取出-->
    <insert id="addUser" parameterType="org.itheima.pojo.User">
        insert into test.users(id,name,age) values (#{id},#{name},#{age});
    </insert>

    <delete id="deleteAUser" parameterType="int">
        delete from users where id = #{id}
    </delete>

    <update id="updateAUser" parameterType="org.itheima.pojo.User">
        update users set age = #{age} , name = #{name} where id = #{id}
    </update>

    <select id="findAllUser" resultType="org.itheima.pojo.User">
        select * from users
    </select>
<!--
    <select id="findUsers" resultType="user">
        select * from users
    </select> -->
</mapper>

pom.xml

<?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.ithema</groupId>
    <artifactId>MybatiesTest</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <maven.compiler.source>16</maven.compiler.source>
        <maven.compiler.target>16</maven.compiler.target>
    </properties>

    <dependencies>

        <!--mybaties-->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.6</version>
        </dependency>

        <!--单元测试-->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.13.2</version>
            <scope>test</scope>
        </dependency>
        <!--mysql-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.25</version>
            <scope>runtime</scope>
        </dependency>
    </dependencies>
    <build>
        <resources>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>true</filtering>
            </resource>
        </resources>
    </build>
</project>

db.properties

mysql.driver=com.mysql.cj.jdbc.Driver
mysql.username=
mysql.password=
mysql.url=jdbc:mysql://localhost:3306/test?serverTimezone=UTC&characterEncoding=utf8&useUnicode=true&useSSL=false&allowPublicKeyRetrieval=true