mybatis使用注解开发

1. mybatis常用注解

   

2. 使用注解方式开发持久层接口

   public interface UserMapper {
   
       /**
        * 查询所有用户
        * @return
        */
       @Select("select * from user")
       List<User> selectAll();
   
       /**
        * 更新用户
        * @param user
        */
       @Update("update user set username=#{username} where id=#{id}")
       void updateUser(User user);
   
       /**
        * 删除用户
        * @param userId
        */
       @Delete("delete from user where id=#{id}")
       void deleteUser(Integer userId);
   
       /**
        * 根据id查询用户
        * @param userId
        * @return
        */
       @Select("select * from user where id=#{id}")
       User findById(Integer userId);
   }
   
   

3. mybatis-config.xml的编写

   <?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>
       <!--引入外部配置文件-->
       <properties resource="db.properties"></properties>
       <!--配置别名-->
       <typeAliases>
           <package name="com.test.User"/>
       </typeAliases>
       <!--配置环境-->
       <environments default="development">
           <environment id="development">
               <transactionManager type="JDBC"></transactionManager>
               <dataSource type="POOLED">
                   <property name="driver" value="${jdriver}"></property>
                   <property name="url" value="${url}"></property>
                   <property name="username" value="${username}"></property>
                   <property name="password" value="${password}"></property>
               </dataSource>
           </environment>
       </environments>
       <!--指定带有注解的dao接口所在位置-->
       <mappers>
           <package name="com.test.dao"></package>
       </mappers>
   </configuration>
   

4. 注解的本质是反射机制