MyBatis —— 主配置文件中的常见标签使用

<!--mapper.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">
<!--namespace：名称空间，对应mapper接口-->
<mapper namespace="com.sangyu.mapper.EmployeeMapper">
    <select id="getEmpById" resultType="com.sangyu.bean.Employee">
     select * from tbl_employee where id = #{id}
</select>

    @Test
    public void Test01() throws IOException {
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream); // 根据xml创建sqlSessionFactory
        SqlSession session = sqlSessionFactory.openSession(); // 2. 从 SqlSessionFactory 中获取 SqlSession 的实例，SqlSession 提供了在数据库执行 SQL 命令所需的所有方法。你可以通过 SqlSession 实例来直接执行已映射的 SQL 语句
        try {
            // 3. 获取接口的实现类对象
            EmployeeMapper mapper = session.getMapper(EmployeeMapper.class);
            Employee employee = mapper.getEmpById(1);
            System.out.println(employee);
        } finally {
            session.close();
        }
    }

// 执行结果
Employee{id=1, lastName='null', email='aa@aa.com', gender='1'}

<?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>
    <properties resource="dbconfig.properties"/>
    <!-- settings 包含很多重要的设置项，
            setting：用来设置每一个设置项
                    name：设置配置项名
                    value：设置项取值 -->

    <!-- mapUnderscoreToCamelCase 是否开启驼峰命名自动映射，即从经典数据库列表名A_COLUMN映射到Java的属性名aColumn-->
    <settings>
        <setting name="mapUnderscoreToCamelCase" value="true"/>
    </settings>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <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>
    <mappers>
        <mapper resource="mapper/EmployeeMapper.xml"/>
    </mappers>
</configuration>

// 执行结果
Employee{id=1, lastName='aa', email='aa@aa.com', gender='1'}

<?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>
    <properties resource="dbconfig.properties"/>
    <settings>
        <setting name="mapUnderscoreToCamelCase" value="true"/>
    </settings>
    <!--typeAliases 别名处理器；可以为我们的java类型起别名，别名不区分大小写  -->
    <typeAliases>
<!--        type :执行要起别名的类型全类名。默认别名就是类型小写，所以此处为：employee-->
        <typeAlias type="com.sangyu.bean.Employee"/>
    </typeAliases>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <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>
    <mappers>
        <mapper resource="mapper/EmployeeMapper.xml"/>
    </mappers>
</configuration>

<?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">
    <select id="getEmpById" resultType="employee">
     select * from tbl_employee where id = #{id}
    </select>
</mapper>

<typeAliases>
      <!--type :执行要起别名的类型全类名。默认别名就是类型小写，所以此处为：employee
      alias： 属性指定新的别名-->
    <typeAlias type="com.sangyu.bean.Employee" alias="emp"/>
</typeAliases>

<select id="getEmpById" resultType="emp">
     select * from tbl_employee where id = #{id}
</select>

 <typeAliases>
    <!--为某个包下的所有类批量起别名
        name: 指定包名（为当前包以及下面所有的后代包的每一个类都起一个默认别名（类名小名））-->
    <package name="com.sangyu.bean"/>
</typeAliases>

@Alias("emp")
public class Employee {
    private Integer id;
    private String lastName;
    private String email;
    private String gender;

 <!--environments 指定运行环境，mybatis可以配置多种环境
    default 指定使用某种环境。可以达到快速切换环境
    environment：配置一个具体的环境信息；必须有两个标签id和transactionManager
    id:代笔当前环境的唯一标识
    transactionManager：事务管理器 ，
            type：事务管理器的类型 JDBC| MANAGED|自定义事务管理器：实现TransactionFactory接口，type指定为全类名
            
    dataSource：数据源
            type：数据源类型 UNPOOLED|POOLED|JNDI|自定义数据源：实现DataSourceFactory接口，type是全类名-->
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <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>

<!--将写好的sql映射文件（mapper.xml）注册到全局配置文件-->
<mappers>
    <!--mapper:注册一个sql映射
    resource：引用类路径下的sql映射文件
    url：应用网络路径或者磁盘路径下的sql映射文件-->
    <mapper resource="mapper/EmployeeMapper.xml"/>
</mappers>

<!--class：引用（注册）接口 
         有sql 映射文件，映射文件必须和接口同名，并且放在与接口同一目录下-->
<mapper class="com.sangyu.mapper.EmployeeMapper"/>

public interface EmployeeMapper {
    @Select("select * from tal_employee where id = #{id}")
    public Employee getEmpById(Integer id);
}