mybatis提取共用代码

  mybatis项目dao层中很多sql语句都会拥有某些相同的查询条件,以<where><if test=””></if></where>的形式拼接在sql语句后,一个两个的sql语句感觉不到什么,但是如果查询语句特别多,但是查询的条件总是类似的,那就可以考虑把<where><if>这部分代码抽取出来,封装一下,然后需要条件搜索的sql语句直接引用就可以了。

  先来看下没有抽取代码之前的条件sql语句

第一条
<select id = "getUserEmailByProvinceAndOrderType" resultType="String">
        select DISTINCT(wo_responsibility) from t_view_workorder
        <where>
            <if test="province != '全国' and province != null">
                wo_province = #{province}
            </if>
            <if test="orderType != '全部' and orderType != null">
                and wo_type = #{orderType}
            </if>
            <if test="email != ''">
                and wo_responsibility = #{email}
            </if>
        </where>
</select>
第二条
<select id = "getUndoneDelayOrderByProvinceAndOrderTypeAndUserEmail" resultType="com.chinamobile.sias.workorder.po.Workorder">
        select * from t_view_workorder
        <where>
        <if test="province != '全国' and province != null">
                wo_province = #{province}
            </if>
            <if test="orderType != '全部' and orderType != null"> and wo_type = #{orderType} </if> <if test="email != ''"> and wo_responsibility = #{email} </if>
        <if test="true"> and (wo_complete_time is null or wo_complete_time='') and (select curdate()) >= wo_regulations_time </if>

    </where>

</select>

以上是两条sql语句,可以看出,两个sql语句中有某些查询条件是相同的

        <if test="province != '全国' and province != null">
            wo_province = #{province}
        </if>
        <if test="orderType != '全部' and orderType != null">
            and wo_type = #{orderType}
        </if>
        <if test="email != ''">
            and wo_responsibility = #{email}
        </if>    

此时我们就可以对此段判断条件进行提取。如下:

<sql id="common_where_if">
        <if test="province != '全国' and province != null">
            wo_province = #{province}
        </if>
        <if test="orderType != '全部' and orderType != null">
            and wo_type = #{orderType}
        </if>
        <if test="email != ''">
            and wo_responsibility = #{email}
        </if>
</sql>

此时把<where>标签下相同的判断条件提去了出来,id自己取,这里定为 common_where_if.

那么如何使用这段代码呢,如下:

<include refid="common_where_if"/>

格式如下:

<select id = "getUserEmailByProvinceAndOrderType" resultType="String">
        select DISTINCT(wo_responsibility) from t_view_workorder
        <where>
            <include refid="common_where_if"/>
        </where>

</select>

此时就在<where>标签中引用了共用的判断条件,再多的sql语句,再多的查询条件,只需要一个<include>就能解决重复的代码。

 

    原文作者:MyBatis
    原文地址: https://www.cnblogs.com/EnzoDin/p/6445281.html
    本文转自网络文章,转载此文章仅为分享知识,如有侵权,请联系博主进行删除。
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