mybatis註解使用
1.簡單crud
public interface UserMapper {
//查詢
@Select("select * from user where id=#{id}")
User selectUser(int id);
//查詢全部
@Select("select * from user")
List<User> selectUserList();
//增加數據
@Insert("insert into user (name) values(#{name})")
boolean insertUser(String name);
//修改用戶
@Update("update user set name=#{name} where id=#{id}")
boolean updateUser(@Param("name") String name,@Param("id") int id);
//刪除用戶
@Delete("delete from user where id=#{id}")
boolean deleteUser(int id);
}
2.一對一註解
@Select("select * from user")
@Results({
@Result(id = true,property = "id",column = "id"),//id=true 對應於主鍵
@Result(property = "uid",column = "uid"),
@Result(property = "user",column = "uid",javaType = User.class,
one = @One(select = "com.example.dao.UserDao.findUserByid",fetchType = FetchType.DEFAULT))
//user 對應實體類中一對一的實體類名字,uid表示通過uid外鍵查詢User,JavaType表示查詢結果
//映射成User類型對象,one=表示一對xx fetchType.default默認是立即加載全部查詢,使用lazy懶加載需要才查詢
})
List<User> selectUserList();
3,一對多註解
@Select("select * from user")
@Results({
@Result(id = true,property = "id",column = "id"),//id=true 對應於主鍵
@Result(property = "uid",column = "uid"),
@Result(property = "user",column = "uid",javaType = User.class,
many = @Many(select = "com.example.dao.UserDao.findUserByid",fetchType = FetchType.DEFAULT))
//user 對應實體類中一對一的實體類名字,uid表示通過uid外鍵查詢User,JavaType表示查詢結果
//映射成User類型對象,one=表示一對xx fetchType.default默認是立即加載全部查詢,使用lazy懶加載需要才查詢
})
List<User> selectUserList();
mybatis的xml配置
1.配置resultMap
<resultMap id="BaseResultMap" type="xx" >
<id column="id" property="ID" jdbcType="BIGINT" />
<result column="aa" property="aa" jdbcType="VARCHAR" />
<result column="bb" property="bb" jdbcType="INTEGER" />
<result column="cc" property="cc" jdbcType="DECIMAL" javaType="java.math.BigDecimal" />
<result column="dd" property="dd" jdbcType="DATE" />
</resultMap>
2.通用sql短語
<sql id="Base_Column_List" >
aa, bb
</sql>
<sql id="where">
<trim prefix="WHERE" prefixOverrides="AND|OR">
<if test="id != null and id != ''">
AND t.ID = #{id}
</if>
<if test="content != null and content != ''">
AND t.CONTENT LIKE concat('%', #{content},'%')
</if>
AND t.APP_CODE IN
<foreach item="item" index="index" collection="appcodes"
open="(" separator="," close=")">
#{item}
</foreach>
and t.USER_ID=u.id and t.REMOVED=0
</trim>
</sql>
3.需要驗證的插入
<insert id="insert" parameterType="xxx"
useGeneratedKeys="true" keyColumn="id" keyProperty="id">
insert into xxx (
<trim suffixOverrides=",">
<if test="title != null and title != '' ">
TITLE ,
</if>
</trim>
) VALUES (
<trim suffixOverrides=",">
<if test="title != null and title != '' ">
#{title} ,
</if>
</trim>
)
</insert>
4.需要驗證的更新
<update id="update" parameterType="xxx">
UPDATE xxx
<set>
<if test="title != null and title != '' ">
TITLE = #{title} ,
</if>
</set>
WHERE
ID = #{id}
</update>
5.<!--批量更新ticketid和SeatNo-->
<update id="xxxUpdate" parameterType="java.util.List">
update xxx
<trim prefix="set" suffixOverrides=",">
<trim prefix="AA =case" suffix="end,">
<foreach collection="orders" item="item" index="index">
<if test="item.aa !=null">
when ID=#{item.id} then #{item.aa}
</if>
</foreach>
</trim>
<trim prefix="BB =case" suffix="end,">
<foreach collection="orders" item="item" index="index">
<if test="item.bb !=null">
when ID=#{item.id} then #{item.bb}
</if>
</foreach>
</trim>
</trim>
where ID in
<foreach collection="orders" index="index" item="item" separator="," open="(" close=")">
#{item.id,jdbcType=BIGINT}
</foreach>
</update>
使case when求和算數sql
SELECT
sum(
CASE
WHEN `REMOVED` = 0 THEN
1
ELSE
0
END
)
FROM
xxx;
mybatis可以使用string給數據庫int類型賦值
springboot中開啓日誌
#mybatis.configuration.log-impl=org.apache.ibatis.logging.stdout.StdOutImpl
1.ORDER BY ${columnName}
這裏 MyBatis 不會修改或轉義字符串。NOTE 用這種方式接受用戶的輸入,並將其用於語句中的參數是不安全的,會導致潛在的 SQL 注入攻擊,因此要麼不允許用戶輸入這些字段,要麼自行轉義並檢驗。
2.如何使用連接池。
首先實例化連接池數據源對象,讓他實現DataSourceFactory這個接口。然後實現方法。在mybatis。conf文件中設置數據連接池這個類,將數據庫連接信息放在config.properties文件中。
3.mybatis.config文件中setting和數據源的設置參數區別
會被覆蓋。
4.連接參數查詢順序
首先查詢properties文件,然後查詢resource文件,最後查詢方法參數。重複的話會被覆蓋。
5.druid連接池配置方式:
詳見官網
DruidDataSourceFactory首先實行setproperties方法,然後返回設置數據源方法。drui數據源也需要在DataSource中設置properties文件
8.實體類的方法不定義也可以進行映射
9.mybatis默認是事務不提交