ibatis 中isNull, isNotNull与isEmpty, isNotEmpty区别

1. <spanstyle="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：

[html]view plaincopy

1. <selectid="getCustomerRegNum"resultClass="int"parameterClass="QueryCustomerCondition">

2.          select count(cus_id) from cus_customer_tbl  

3. <dynamicprepend="WHERE">

4. <isNotEmptyprepend="AND"property="cusWebFrom">

5.                ( CUS_CUSTOMER_TBL.CUS_WEB_FROM LIKE '%$cusWebFrom$%')  

6. </isNotEmpty>

7. <isNotEmptyprepend="AND"property="cusWebAgent">

8.                ( CUS_CUSTOMER_TBL.CUS_WEB_AGENT LIKE '%$cusWebAgent$%')  

9. </isNotEmpty>

10. </dynamic>

11. </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），

[html]view plaincopy

1. <selectid="getCustomerRegNum"resultClass="int"parameterClass="QueryCustomerCondition">

2.          select count(cus_id) from cus_customer_tbl  

3. <dynamicprepend="WHERE">

4. <isNotNullprepend="AND"property="cusWebFrom">

5.                ( CUS_CUSTOMER_TBL.CUS_WEB_FROM LIKE '%$cusWebFrom$%')  

6. </isNotNull>

7. <isNotNullprepend="AND"property="cusWebAgent">

8.                ( CUS_CUSTOMER_TBL.CUS_WEB_AGENT LIKE '%$cusWebAgent$%')  

9. </isNotNull>

10. </dynamic>

11. </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 '%%')