mybatis foreach,trim标签

你的名字 2022-04-24 01:26 253阅读 0赞

批量插入数据使用的sql语句是：

insert into table (aa,bb,cc) values(xx,xx,xx),(oo,oo,oo)

<insert id="insertBatch" parameterType="java.util.List"
            useGeneratedKeys="true">
            <selectKey resultType="long" keyProperty="id" order="AFTER">
                SELECT
                LAST_INSERT_ID()
            </selectKey>
            insert into wd_solr
            (fayu_id, tablename,
            name,logo,description,section_no,look_count,favorite_count,create_uid,create_time,update_time,timestamp)
            values
            <foreach collection="list" item="wdSolr" index="index"
                separator=",">
                (
                #{wdSolr.fayuId},#{wdSolr.tablename},#{wdSolr.name},#{wdSolr.logo},
                #{wdSolr.description},#{wdSolr.sectionNo},#{wdSolr.lookCount},#{wdSolr.favoriteCount},
                #{wdSolr.createUid},#{wdSolr.createTime},#{wdSolr.updateTime},#{wdSolr.timestamp}
                )
            </foreach>
        </insert>

批量更新数据使用的sql语句是：

UPDATE table
        SET aa = CASE id
            WHEN 1 THEN 'oo'
            WHEN 2 THEN 'pp'
            WHEN 3 THEN 'qq'
        END
    　 ,SET bb = CASE id
            WHEN 1 THEN 'xx'
            WHEN 2 THEN 'yy'
            WHEN 3 THEN 'zz'
        END
    WHERE id IN (1,2,3)

**上面这一条mysql语句可以更新多条记录**，mybatis中mapper.xml的代码如下：

<update id="updateBatch">
            update wd_solr set
            name =
            <foreach collection="list" item="wdSolr" index="index"
                separator=" " open="case id" close="end">
                when #{wdSolr.id} then
                #{wdSolr.name}
            </foreach>
            ,logo =
            <foreach collection="list" item="wdSolr" index="index"
                separator=" " open="case id" close="end">
                when #{wdSolr.id} then
                #{wdSolr.logo}
            </foreach>        
            ,timestamp =
            <foreach collection="list" item="wdSolr" index="index"
                separator=" " open="case id" close="end">
                when #{wdSolr.id} then #{wdSolr.timestamp}
            </foreach>
            where id in
            <foreach collection="list" item="wdSolr" index="index" 
                separator="," open="(" close=")">
                #{wdSolr.id}
            </foreach>
        </update>

trim代替where/set标签

trim 是更灵活用来去处多余关键字的标签，它可以用来实现 where 和 set 的效果。原文出自【易百教程】，商业转载请联系作者获得授权，非商业转载请保留原文链接：https://www.yiibai.com/mybatis/mybaits\_trim.html

<select id="getUsertList_if_trim" resultMap="resultMap_User">  
        SELECT * 
          FROM user u
        <trim prefix="WHERE" prefixOverrides="AND|OR">  
            <if test="username !=null ">  
                u.username LIKE CONCAT(CONCAT('%', #{username, jdbcType=VARCHAR}),'%')  
            </if>  
            <if test="sex != null and sex != '' ">  
                AND u.sex = #{sex, jdbcType=INTEGER}  
            </if>  
            <if test="birthday != null ">  
                AND u.birthday = #{birthday, jdbcType=DATE}  
            </if>
        </trim>     
    </select>

trim 代替 set

<update id="updateUser_if_trim" parameterType="com.yiibai.pojo.User">  
        UPDATE user  
        <trim prefix="SET" suffixOverrides=",">  
            <if test="username != null and username != '' ">  
                username = #{username},  
            </if>  
            <if test="sex != null and sex != '' ">  
                sex = #{sex},  
            </if>  
            <if test="birthday != null ">  
                birthday = #{birthday},  
            </if>  
             
        </trim>  
        WHERE user_id = #{user_id}  
    </update>

trim (对包含的内容加上 prefix,或者 suffix 等，前缀，后缀)

<select id="dynamicTrimTest" parameterType="Blog" resultType="Blog">
            select * from t_blog 
            <trim prefix="where" prefixOverrides="and |or">
                <if test="title != null">
                    title = #{title}
                </if>
                <if test="content != null">
                    and content = #{content}
                </if>
                <if test="owner != null">
                    or owner = #{owner}
                </if>
            </trim>
        </select>

trim 元素的主要功能是可以在自己包含的内容前加上某些前缀，也可以在其后加上某些后缀，与之对应的属性是 prefix 和 suffix；可以把包含内容的首部某些内容覆盖，即忽略，也可以把尾部的某些内容覆盖，对应的属性是 prefixOverrides 和 suffixOverrides；正因为 trim 有这样的功能，所以我们也可以非常简单的利用 trim 来代替 where 元素的功能。