ibatis 中isNull, isNotNull与isEmpty, isNotEmpty区别

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<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

如下代码：

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<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 [b]cusWebAgent 时，产生的SQL语句为：[/b]

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），



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<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。。。。。