Mybatis

1 创建Maven使用mybatis

1.1 设置

1设置Maven->conf 设置默认JDK
	<profile>
		<id>jdk11</id>
		<activation>
			<activeByDefault>true</activeByDefault>
			<jdk>11</jdk>
		</activation>
		<properties>
			<maven.compiler.source>11</maven.compiler.source>
			<maven.compiler.target>11</maven.compiler.target>
			<maven.compiler.compilerVersion>11</maven.compiler.compilerVersion>
		</properties>
	</profile>
2.设置本地仓库
3.设置阿里云镜像

1.2 导入依赖

		<dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.4</version>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.28</version>
        </dependency>

1.3 在IDEA中连接MySQL

1.修改默认模板SQL
2.导入实体类

1.4 编写主配置文件(mybatis-config.xml)(IDEA mybatis 模板)

1.4.1 从官网复制修改即可

    <?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.cj.jdbc.Driver"/>
                    <property name="url" value="jdbc:mysql:///mybatis"/>
                    <property name="username" value="root"/>
                    <property name="password" value="root"/>
                </dataSource>
            </environment>
        </environments>
    <!--    <mappers>-->
    <!--        <mapper resource="org/mybatis/example/BlogMapper.xml"/>-->
    <!--    </mappers>-->
    </configuration>

1.4.2 模板settings->Editor->File and Code Templates->Files

1.5 编写Mapper映射文件

<?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="">
    
</mapper>

2. MyBatis的mapper开发

2.1 定义接口

public interface UserMapper {
    // 查询所有用户
    List<User> selectAll();
}

2.2 编写xml

<?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=""> 接口路径 例如：com.aaa.mapper.UserMapper
    <select id="selectdAll" resultType="">实体类路径 例如：com.aaa.entity.User
        select * from user
    </select>
</mapper>

3.全局配置(mybatis-config.xml)

3.1 开启mybatis日志

<!--开启mybatis的日志-->
    <setting name="logImpl" value="STDOUT_LOGGING"/>
</settings>

3.2 别名标签

	<typeAliases>
<!--对一个实体类起别名-->
		<typeAlias type="com.aaa.entity.User" alias="user"></typeAlias>
<!--对包整体起别名  默认别名就是类名 不区分大小写-->
        <package name="com.aaa.entity"/>
    </typeAliases>

3.3 mapper 标签

要求Maven 的resoures下的xml文件和src下的接口文件**同名同目录**
<mappers>
  <package name="com.aaa.mapper"/>
</mappers>

3.4 延迟加载

<!--开启懒加载-->
<setting name="lazyLoadingEnabled" value="true"/>