[Java知识库]Mybatis的核心配置文件

Mybatis的核心配置文件

1、Mybatis的核心配置文件层级关系

2、environments标签

数据库环境的配置，支持多环境配置

3、mapper标签

4、properties标签

在resource包下创建名为jdbc.properties的file文件

jdbc.driver=com.mysql.cj.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/test
jdbc.username=root
jdbc.password=011012

修改sqlMapConfig.xml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>
    <!--通过properties标签加载外部properties文件-->
    <properties resource="jdbc.properties"></properties>
    <!--数据源环境-->
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"></transactionManager>
            <dataSource type="POOLED">
                <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>
    <!--加载映射文件-->
    <mappers>
        <mapper resource="com\mapper\UserMapper.xml"></mapper>
    </mappers>
</configuration>

5、typeAliases标签

现在修改UserMapper.xml文件

<?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="userMapper">
    <!--删除操作-->
    <delete id="delete" parameterType="int">
        delete from where id=#{id}
    </delete>
    <!--修改操作-->
    <update id="update" parameterType="com.domain.User">
        update user set username=#{username},password=#{password} where id=#{id}
    </update>
    <!--插入操作-->
    <insert id="save" parameterType="com.domain.User">
        insert into user values(#{id},#{username},#{password})
    </insert>

    <!--查询操作-->
    <select id="findAll" resultType="user">
        select  * from user
    </select>
</mapper>

在来运行test01,发现只有int修改可以，而自定义的user则报错，原因是user没有自定义，修改sqlMapConfig.xml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>
    <!--通过properties标签加载外部properties文件-->
    <properties resource="jdbc.properties"></properties>

    <!--自定义别名-->
    <typeAliases>
        <typeAlias type="com.domain.User" alias="user"></typeAlias>
    </typeAliases>

    <!--数据源环境-->
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"></transactionManager>
            <dataSource type="POOLED">
                <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>
    <!--加载映射文件-->
    <mappers>
        <mapper resource="com\mapper\UserMapper.xml"></mapper>
    </mappers>
</configuration>

PS：注意添加的顺序
在运行test01