MyBatis注解全面指南<\/h1>

一、注解基础概念<\/h2>

1. 注解定义<\/h3>
注解(Annotation)是从JDK1.5开始引入的技术，是一种用于描述代码的元数据，可以被编译器、库和其他工具读取和使用。<\/p>

2. 注解特性<\/h3>

格式<\/strong>：以@注解名<\/code>的方式实现，可带参数值，如@SuppressWarnings(value="unchecked")<\/code><\/li>
作用位置<\/strong>：package、class、method、field等<\/li>

作用<\/strong>：为代码提供额外辅助信息，不是程序本身<\/li> <\/ul> 3. 注解分类<\/h3> 元注解<\/strong>：<\/p> @Target<\/code>：描述注解使用范围<\/li> @Retention<\/code>：描述注解生命周期<\/li> @Documented<\/code>：说明注解将被包含在javadoc中<\/li> @Inherited<\/code>：说明子类可继承父类中的该注解<\/li> @Repeatable<\/code>：可重复注解<\/li> <\/ul> <\/li> 内置注解<\/strong>：<\/p> @Override<\/code>：重写检查<\/li> @Deprecated<\/code>：标记过时<\/li> @SuppressWarnings<\/code>：压制警告<\/li> @FunctionalInterface<\/code>：函数式接口<\/li> <\/ul> <\/li> 自定义注解<\/strong>：<\/p> public<\/span> @interface<\/span> MyAnno {}<\/span> <\/span><\/span><\/code><\/pre><\/li> <\/ol> 二、MyBatis注解使用基础<\/h2> 1. 基本配置步骤<\/h3> 全局配置文件中配置映射<\/strong>：<\/p> <mappers><\/span> <\/span><\/span> <mapper<\/span> class=<\/span>"com.cy.mybatis.mapper.UserMapper"<\/span>\/><\/span> <\/span><\/span><\/mappers><\/span> <\/span><\/span><\/code><\/pre><\/li> 在Mapper接口方法上添加注解<\/strong>：<\/p> @Select<\/span>(<\/span>"select * from user where uid = #{uid}"<\/span>)<\/span> <\/span><\/span>public<\/span> User findUserById<\/span>(<\/span>int<\/span> uid);<\/span> <\/span><\/span><\/code><\/pre><\/li> 创建会话调用方法<\/strong><\/p> <\/li> <\/ol> 三、MyBatis核心注解详解<\/h2> 1. CRUD操作注解<\/h3> @Select<\/h4> 作用<\/strong>：标记查询语句<\/li> 示例<\/strong>： @Select<\/span>(<\/span>"SELECT * FROM users WHERE id = #{id}"<\/span>)<\/span> <\/span><\/span>User getUserById<\/span>(<\/span>@Param<\/span>(<\/span>"id"<\/span>)<\/span> Long id);<\/span> <\/span><\/span><\/code><\/pre><\/li> <\/ul> @Insert<\/h4> 作用<\/strong>：标记插入语句<\/li> 示例<\/strong>： @Insert<\/span>(<\/span>"INSERT INTO users(name, age) VALUES(#{name}, #{age})"<\/span>)<\/span> <\/span><\/span>int<\/span> addUser<\/span>(<\/span>User user);<\/span> <\/span><\/span><\/code><\/pre><\/li> <\/ul> @Update<\/h4> 作用<\/strong>：标记更新语句<\/li> 示例<\/strong>： @Update<\/span>(<\/span>"UPDATE users SET name = #{name}, age = #{age} WHERE id = #{id}"<\/span>)<\/span> <\/span><\/span>int<\/span> updateUser<\/span>(<\/span>User user);<\/span> <\/span><\/span><\/code><\/pre><\/li> <\/ul> @Delete<\/h4> 作用<\/strong>：标记删除语句<\/li> 示例<\/strong>： @Delete<\/span>(<\/span>"DELETE FROM users WHERE id = #{id}"<\/span>)<\/span> <\/span><\/span>int<\/span> deleteUserById<\/span>(<\/span>@Param<\/span>(<\/span>"id"<\/span>)<\/span> Long id);<\/span> <\/span><\/span><\/code><\/pre><\/li> <\/ul> 2. 结果映射注解<\/h3> @Results<\/h4> 作用<\/strong>：指定多个@Result注解<\/li> 示例<\/strong>： @Select<\/span>(<\/span>"SELECT * FROM users WHERE id = #{id}"<\/span>)<\/span> <\/span><\/span>@Results<\/span>(<\/span>id =<\/span> "userResultMap"<\/span>,<\/span> value =<\/span> {<\/span> <\/span><\/span> @Result<\/span>(<\/span>property =<\/span> "id"<\/span>,<\/span> column =<\/span> "id"<\/span>),<\/span> <\/span><\/span> @Result<\/span>(<\/span>property =<\/span> "name"<\/span>,<\/span> column =<\/span> "name"<\/span>),<\/span> <\/span><\/span> @Result<\/span>(<\/span>property =<\/span> "age"<\/span>,<\/span> column =<\/span> "age"<\/span>)<\/span> <\/span><\/span>})<\/span> <\/span><\/span>User getUserById<\/span>(<\/span>@Param<\/span>(<\/span>"id"<\/span>)<\/span> Long id);<\/span> <\/span><\/span><\/code><\/pre><\/li> <\/ul> @Result<\/h4> 作用<\/strong>：指定单个属性与结果集列的映射关系<\/li> 使用场景<\/strong>：与@Results配合使用<\/li> <\/ul> @ResultMap<\/h4> 作用<\/strong>：引用已定义的结果集映射<\/li> 示例<\/strong>： @Select<\/span>(<\/span>"SELECT * FROM users WHERE id = #{id}"<\/span>)<\/span> <\/span><\/span>@ResultMap<\/span>(<\/span>"userResultMap"<\/span>)<\/span> <\/span><\/span>User getUserById<\/span>(<\/span>@Param<\/span>(<\/span>"id"<\/span>)<\/span> Long id);<\/span> <\/span><\/span><\/code><\/pre><\/li> <\/ul> 3. 主键处理注解<\/h3> @Options<\/h4> 作用<\/strong>：指定插入语句选项<\/li> 常用参数<\/strong>： useGeneratedKeys<\/code>：是否使用生成的主键<\/li> keyProperty<\/code>：主键属性名<\/li> <\/ul> <\/li> 示例<\/strong>： @Insert<\/span>(<\/span>"INSERT INTO users(name, age) VALUES(#{name}, #{age})"<\/span>)<\/span> <\/span><\/span>@Options<\/span>(<\/span>useGeneratedKeys =<\/span> true<\/span>,<\/span> keyProperty =<\/span> "id"<\/span>)<\/span> <\/span><\/span>int<\/span> insertUser<\/span>(<\/span>User user);<\/span> <\/span><\/span><\/code><\/pre><\/li> <\/ul> @SelectKey<\/h4> 作用<\/strong>：获取自动生成的主键值<\/li> 示例<\/strong>： @Insert<\/span>(<\/span>"INSERT INTO users(name, age) VALUES(#{name}, #{age})"<\/span>)<\/span> <\/span><\/span>@SelectKey<\/span>(<\/span>statement =<\/span> "SELECT LAST_INSERT_ID()"<\/span>,<\/span> <\/span><\/span> keyProperty =<\/span> "id"<\/span>,<\/span> <\/span><\/span> before =<\/span> false<\/span>,<\/span> <\/span><\/span> resultType =<\/span> Long.<\/span>class<\/span>)<\/span> <\/span><\/span>int<\/span> insertUser<\/span>(<\/span>User user);<\/span> <\/span><\/span><\/code><\/pre><\/li> <\/ul> 4. 参数处理注解<\/h3> @Param<\/h4> 作用<\/strong>：指定方法参数名称<\/li> 示例<\/strong>： @Select<\/span>(<\/span>"SELECT * FROM users WHERE name = #{name} AND age = #{age}"<\/span>)<\/span> <\/span><\/span>List<<\/span>User><\/span> getUsersByNameAndAge<\/span>(<\/span>@Param<\/span>(<\/span>"name"<\/span>)<\/span> String name,<\/span> @Param<\/span>(<\/span>"age"<\/span>)<\/span> Integer age);<\/span> <\/span><\/span><\/code><\/pre><\/li> <\/ul> 5. 关联关系注解<\/h3> @One<\/h4> 作用<\/strong>：指定一对一关联关系<\/li> XML示例<\/strong>： <resultMap<\/span> id=<\/span>"departmentResultMap"<\/span> type=<\/span>"Department"<\/span>><\/span> <\/span><\/span> <id<\/span> column=<\/span>"id"<\/span> property=<\/span>"id"<\/span>\/><\/span> <\/span><\/span> <result<\/span> column=<\/span>"name"<\/span> property=<\/span>"name"<\/span>\/><\/span> <\/span><\/span> <result<\/span> column=<\/span>"description"<\/span> property=<\/span>"description"<\/span>\/><\/span> <\/span><\/span> <one<\/span> property=<\/span>"manager"<\/span> resultMap=<\/span>"userResultMap"<\/span>\/><\/span> <\/span><\/span><\/resultMap><\/span> <\/span><\/span><\/code><\/pre><\/li> <\/ul> @Many<\/h4> 作用<\/strong>：指定一对多关联关系<\/li> XML示例<\/strong>： <resultMap<\/span> id=<\/span>"departmentResultMap"<\/span> type=<\/span>"Department"<\/span>><\/span> <\/span><\/span> <id<\/span> column=<\/span>"id"<\/span> property=<\/span>"id"<\/span>\/><\/span> <\/span><\/span> <result<\/span> column=<\/span>"name"<\/span> property=<\/span>"name"<\/span>\/><\/span> <\/span><\/span> <result<\/span> column=<\/span>"description"<\/span> property=<\/span>"description"<\/span>\/><\/span> <\/span><\/span> <collection<\/span> property=<\/span>"members"<\/span> ofType=<\/span>"User"<\/span> resultMap=<\/span>"userResultMap"<\/span>\/><\/span> <\/span><\/span><\/resultMap><\/span> <\/span><\/span><\/code><\/pre><\/li> <\/ul> 6. 类型处理注解<\/h3> @ResultType<\/h4> 作用<\/strong>：指定查询结果集类型<\/li> 示例<\/strong>： @Select<\/span>(<\/span>"SELECT name, age FROM users WHERE id = #{id}"<\/span>)<\/span> <\/span><\/span>@ResultType<\/span>(<\/span>User.<\/span>class<\/span>)<\/span> <\/span><\/span>User getUserById<\/span>(<\/span>Long id);<\/span> <\/span><\/span><\/code><\/pre><\/li> <\/ul> @TypeDiscriminator<\/h4> 作用<\/strong>：指定类型鉴别器<\/li> XML示例<\/strong>： <resultMap<\/span> id=<\/span>"vehicleResultMap"<\/span> type=<\/span>"Vehicle"<\/span>><\/span> <\/span><\/span> <discriminator<\/span> javaType=<\/span>"String"<\/span> column=<\/span>"type"<\/span>><\/span> <\/span><\/span> <case<\/span> value=<\/span>"car"<\/span> resultMap=<\/span>"carResultMap"<\/span>\/><\/span> <\/span><\/span> <case<\/span> value=<\/span>"truck"<\/span> resultMap=<\/span>"truckResultMap"<\/span>\/><\/span> <\/span><\/span> <case<\/span> value=<\/span>"bus"<\/span> resultMap=<\/span>"busResultMap"<\/span>\/><\/span> <\/span><\/span> <\/discriminator><\/span> <\/span><\/span><\/resultMap><\/span> <\/span><\/span><\/code><\/pre><\/li> <\/ul> @Discriminator<\/h4> 作用<\/strong>：指定类型鉴别器的查询结果<\/li> 示例<\/strong>： @Select<\/span>(<\/span>"SELECT * FROM vehicle WHERE type = #{type}"<\/span>)<\/span> <\/span><\/span>@Discriminator<\/span>(<\/span>column =<\/span> "type"<\/span>,<\/span> javaType =<\/span> String.<\/span>class<\/span>,<\/span> cases =<\/span> {<\/span> <\/span><\/span> @Case<\/span>(<\/span>value =<\/span> "car"<\/span>,<\/span> type =<\/span> Car.<\/span>class<\/span>),<\/span> <\/span><\/span> @Case<\/span>(<\/span>value =<\/span> "truck"<\/span>,<\/span> type =<\/span> Truck.<\/span>class<\/span>),<\/span> <\/span><\/span> @Case<\/span>(<\/span>value =<\/span> "bus"<\/span>,<\/span> type =<\/span> Bus.<\/span>class<\/span>)<\/span> <\/span><\/span>})<\/span> <\/span><\/span>List<<\/span>Vehicle><\/span> getVehiclesByType<\/span>(<\/span>String type);<\/span> <\/span><\/span><\/code><\/pre><\/li> <\/ul> 7. 构造方法注解<\/h3> @ConstructorArgs<\/h4> 作用<\/strong>：指定构造方法参数<\/li> XML示例<\/strong>： <resultMap<\/span> id=<\/span>"userResultMap"<\/span> type=<\/span>"User"<\/span>><\/span> <\/span><\/span> <constructor><\/span> <\/span><\/span> <arg<\/span> column=<\/span>"name"<\/span> javaType=<\/span>"String"<\/span>\/><\/span> <\/span><\/span> <arg<\/span> column=<\/span>"age"<\/span> javaType=<\/span>"int"<\/span>\/><\/span> <\/span><\/span> <\/constructor><\/span> <\/span><\/span><\/resultMap><\/span> <\/span><\/span><\/code><\/pre><\/li> <\/ul> @Arg<\/h4> 作用<\/strong>：指定构造方法参数映射<\/li> 示例<\/strong>： @Select<\/span>(<\/span>"SELECT name, age FROM users WHERE id = #{id}"<\/span>)<\/span> <\/span><\/span>User getUserById<\/span>(<\/span>@Arg<\/span>(<\/span>"name"<\/span>)<\/span> String name,<\/span> @Arg<\/span>(<\/span>"age"<\/span>)<\/span> int<\/span> age);<\/span> <\/span><\/span><\/code><\/pre><\/li> <\/ul> 8. 缓存相关注解<\/h3> @CacheNamespace<\/h4> 作用<\/strong>：指定缓存的命名空间<\/li> 示例<\/strong>： @CacheNamespace<\/span>(<\/span> <\/span><\/span> implementation =<\/span> MyBatisRedisCache.<\/span>class<\/span>,<\/span> <\/span><\/span> eviction =<\/span> MyBatisRedisCache.<\/span>Eviction<\/span>.<\/span>LRU<\/span>,<\/span> <\/span><\/span> flushInterval =<\/span> 60000<\/span>,<\/span> <\/span><\/span> size =<\/span> 10000<\/span>,<\/span> <\/span><\/span> readWrite =<\/span> true<\/span>,<\/span> <\/span><\/span> blocking =<\/span> true<\/span>)<\/span> <\/span><\/span>public<\/span> interface<\/span> UserMapper<\/span> {<\/span> <\/span><\/span> @Select<\/span>(<\/span>"SELECT * FROM users WHERE id = #{id}"<\/span>)<\/span> <\/span><\/span> User getUserById<\/span>(<\/span>Long id);<\/span> <\/span><\/span>}<\/span> <\/span><\/span><\/code><\/pre><\/li> <\/ul> @Flush<\/h4> 作用<\/strong>：在执行方法前或后刷新缓存<\/li> 示例<\/strong>： @Select<\/span>(<\/span>"SELECT * FROM users WHERE id = #{id}"<\/span>)<\/span> <\/span><\/span>@Flush<\/span>(<\/span>flushCache =<\/span> FetchType.<\/span>AFTER<\/span>)<\/span> <\/span><\/span>User getUserById<\/span>(<\/span>Long id);<\/span> <\/span><\/span><\/code><\/pre><\/li> <\/ul> 9. 类型映射注解<\/h3> @MappedJdbcTypes<\/h4> 作用<\/strong>：指定Java类型对应的JDBC类型<\/li> 示例<\/strong>： public<\/span> class<\/span> User<\/span> {<\/span> <\/span><\/span> @MappedJdbcTypes<\/span>(<\/span>JdbcType.<\/span>VARCHAR<\/span>)<\/span> <\/span><\/span> private<\/span> String name;<\/span> <\/span><\/span>}<\/span> <\/span><\/span><\/code><\/pre><\/li> <\/ul> @MappedTypes<\/h4> 作用<\/strong>：指定Java类型<\/li> 示例<\/strong>： @MappedTypes<\/span>(<\/span>User.<\/span>class<\/span>)<\/span> <\/span><\/span>public<\/span> interface<\/span> UserMapper<\/span> {<\/span> <\/span><\/span> @Select<\/span>(<\/span>"SELECT * FROM users WHERE id = #{id}"<\/span>)<\/span> <\/span><\/span> User getUserById<\/span>(<\/span>Long id);<\/span> <\/span><\/span>}<\/span> <\/span><\/span><\/code><\/pre><\/li> <\/ul> 10. 动态SQL提供者注解<\/h3> @SelectProvider<\/h4> 作用<\/strong>：动态生成查询SQL<\/li> 示例<\/strong>： @SelectProvider<\/span>(<\/span>type =<\/span> UserSqlProvider.<\/span>class<\/span>,<\/span> method =<\/span> "getUserByIdSql"<\/span>)<\/span> <\/span><\/span>User getUserById<\/span>(<\/span>Long id);<\/span> <\/span><\/span><\/code><\/pre><\/li> <\/ul> @InsertProvider<\/h4> 作用<\/strong>：动态生成插入SQL<\/li> 示例<\/strong>： @InsertProvider<\/span>(<\/span>type =<\/span> UserSqlProvider.<\/span>class<\/span>,<\/span> method =<\/span> "insertUserSql"<\/span>)<\/span> <\/span><\/span>int<\/span> insertUser<\/span>(<\/span>User user);<\/span> <\/span><\/span><\/code><\/pre><\/li> <\/ul> @UpdateProvider<\/h4> 作用<\/strong>：动态生成更新SQL<\/li> 示例<\/strong>： @UpdateProvider<\/span>(<\/span>type =<\/span> UserSqlProvider.<\/span>class<\/span>,<\/span> method =<\/span> "updateUserSql"<\/span>)<\/span> <\/span><\/span>int<\/span> updateUser<\/span>(<\/span>User user);<\/span> <\/span><\/span><\/code><\/pre><\/li> <\/ul> @DeleteProvider<\/h4> 作用<\/strong>：动态生成删除SQL<\/li> 示例<\/strong>： @DeleteProvider<\/span>(<\/span>type =<\/span> UserSqlProvider.<\/span>class<\/span>,<\/span> method =<\/span> "deleteUserSql"<\/span>)<\/span> <\/span><\/span>int<\/span> deleteUser<\/span>(<\/span>Long id);<\/span> <\/span><\/span><\/code><\/pre><\/li> <\/ul> 四、最佳实践建议<\/h2> 简单查询<\/strong>：优先使用注解方式，代码更简洁<\/li> 复杂SQL<\/strong>：考虑使用XML配置方式，更易维护<\/li> 结果映射<\/strong>：对于复杂对象关系，使用@Results和@ResultMap<\/li> 动态SQL<\/strong>：使用Provider类实现复杂条件查询<\/li> 缓存控制<\/strong>：合理使用@CacheNamespace和@Flush优化性能<\/li> <\/ol> 五、总结<\/h2> MyBatis注解提供了一种简洁高效的SQL映射方式，可以显著减少XML配置的工作量。掌握这些注解的使用方法，能够根据不同的业务场景选择最合适的实现方式，提高开发效率和代码可读性。<\/p>

MyBatis注解全面指南<\/h1>

一、注解基础概念<\/h2>

1. 注解定义<\/h3> 注解(Annotation)是从JDK1.5开始引入的技术，是一种用于描述代码的元数据，可以被编译器、库和其他工具读取和使用。<\/p>

二、MyBatis注解使用基础<\/h2>

1. CRUD操作注解<\/h3>

2. 结果映射注解<\/h3>

3. 主键处理注解<\/h3>

4. 参数处理注解<\/h3>

5. 关联关系注解<\/h3>

6. 类型处理注解<\/h3>

7. 构造方法注解<\/h3>

8. 缓存相关注解<\/h3>

9. 类型映射注解<\/h3>

10. 动态SQL提供者注解<\/h3>

五、总结<\/h2> MyBatis注解提供了一种简洁高效的SQL映射方式，可以显著减少XML配置的工作量。掌握这些注解的使用方法，能够根据不同的业务场景选择最合适的实现方式，提高开发效率和代码可读性。<\/p>

1. 注解定义<\/h3>
注解(Annotation)是从JDK1.5开始引入的技术，是一种用于描述代码的元数据，可以被编译器、库和其他工具读取和使用。<\/p>

五、总结<\/h2>
MyBatis注解提供了一种简洁高效的SQL映射方式，可以显著减少XML配置的工作量。掌握这些注解的使用方法，能够根据不同的业务场景选择最合适的实现方式，提高开发效率和代码可读性。<\/p>