ibatis 中isNull, isNotNull与isEmpty, isNotEmpty区别（转）

　　

<span style="font-family: Arial, Verdana, sans-serif; white-space: normal; "><strong>isNull, isNotNull与isEmpty, isNotEmpty区别</strong></span>

在iBATIS中

isNull用于判断参数是否为Null，isNotNull相反

isEmpty判断参数是否为Null或者空，满足其中一个条件则其true

isNotEmpty相反，当参数既不为Null也不为空是其为true

 判断之后做相对应的表达式操作

 

     <select id="getCustomerRegNum" resultClass="int" parameterClass="QueryCustomerCondition">
            select count(cus_id) from cus_customer_tbl 
            <dynamic prepend="WHERE">
                <isNotEmpty prepend="AND" property="cusWebFrom">
                    ( CUS_CUSTOMER_TBL.CUS_WEB_FROM LIKE '%$cusWebFrom$%')
                </isNotEmpty>
                <isNotEmpty prepend="AND" property="cusWebAgent">
                    ( CUS_CUSTOMER_TBL.CUS_WEB_AGENT LIKE '%$cusWebAgent$%')
                </isNotEmpty>
            </dynamic>
     </select>

当之传入参数 cusWebForm 而不传入 cusWebAgent 时，产生的SQL语句为：

select count(cus_id) from cus_customer_tbl    WHERE      ( CUS_CUSTOMER_TBL.CUS_WEB_FROM LIKE '%baidu%') 

而当XML代码用<isNotNull > 配置时（注意他们的区别），

     <select id="getCustomerRegNum" resultClass="int" parameterClass="QueryCustomerCondition">
            select count(cus_id) from cus_customer_tbl 
            <dynamic prepend="WHERE">
                <isNotNull prepend="AND" property="cusWebFrom">
                    ( CUS_CUSTOMER_TBL.CUS_WEB_FROM LIKE '%$cusWebFrom$%')
                </isNotNull>
                <isNotNull prepend="AND" property="cusWebAgent">
                    ( CUS_CUSTOMER_TBL.CUS_WEB_AGENT LIKE '%$cusWebAgent$%')
                </isNotNull>
            </dynamic>
     </select>

同样 ，当之传入参数 cusWebForm 而不传入 cusWebAgent 时，产生的SQL语句为： 

select count(cus_id) from cus_customer_tbl     WHERE     ( CUS_CUSTOMER_TBL.CUS_WEB_FROM LIKE '%baidu%')      AND        (CUS_CUSTOMER_TBL.CUS_WEB_AGENT LIKE '%%')

 从Sql 语句就能看出他们的区别。。。。。