foreach的主要用在構建in條件中,它可以在SQL語句中進行迭代一個集合。foreach元素的屬性主要有item,index,collection,open,separator,close。item表示集合中每一個元素進行迭代時的別名,index指定一個名字,用於表示在迭代過程中,每次迭代到的位置,open表示該語句以什么開始,separator表示在每次進行迭代之間以什么符號作為分隔符,close表示以什么結束,在使用foreach的時候最關鍵的也是最容易出錯的就是collection屬性,該屬性是必須指定的,但是在不同情況下,該屬性的值是不一樣的,主要有一下3種情況:
如果傳入的是單參數且參數類型是一個List的時候,collection屬性值為list .
如果傳入的是單參數且參數類型是一個array數組的時候,collection的屬性值為array .
如果傳入的參數是多個的時候,我們就需要把它們封裝成一個Map了,當然單參數也可以封裝成map,實際上如果你在傳入參數的時候,在MyBatis里面也是會把它封裝成一個Map的,map的key就是參數名,所以這個時候collection屬性值就是傳入的List或array對象在自己封裝的map里面的key.
下面我們通過代碼實踐:
數據表:
采用Oracle的HR.Employees表
實體:Employees
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public
class
Employees {
private
Integer employeeId;
private
String firstName;
private
String lastName;
private
String email;
private
String phoneNumber;
private
Date hireDate;
private
String jobId;
private
BigDecimal salary;
private
BigDecimal commissionPct;
private
Integer managerId;
private
Short departmentId;
}
|
映射文件:
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<!--List:forech中的collection屬性類型是List,collection的值必須是:list,item的值可以隨意,Dao接口中參數名字隨意 -->
<
select
id
=
"getEmployeesListParams"
resultType
=
"Employees"
>
select *
from EMPLOYEES e
where e.EMPLOYEE_ID in
<
foreach
collection
=
"list"
item
=
"employeeId"
index
=
"index"
open
=
"("
close
=
")"
separator
=
","
>
#{employeeId}
</
foreach
>
</
select
>
<!--Array:forech中的collection屬性類型是array,collection的值必須是:list,item的值可以隨意,Dao接口中參數名字隨意 -->
<
select
id
=
"getEmployeesArrayParams"
resultType
=
"Employees"
>
select *
from EMPLOYEES e
where e.EMPLOYEE_ID in
<
foreach
collection
=
"array"
item
=
"employeeId"
index
=
"index"
open
=
"("
close
=
")"
separator
=
","
>
#{employeeId}
</
foreach
>
</
select
>
<!--Map:不單單forech中的collection屬性是map.key,其它所有屬性都是map.key,比如下面的departmentId -->
<
select
id
=
"getEmployeesMapParams"
resultType
=
"Employees"
>
select *
from EMPLOYEES e
<
where
>
<
if
test
=
"departmentId!=null and departmentId!=''"
>
e.DEPARTMENT_ID=#{departmentId}
</
if
>
<
if
test
=
"employeeIdsArray!=null and employeeIdsArray.length!=0"
>
AND e.EMPLOYEE_ID in
<
foreach
collection
=
"employeeIdsArray"
item
=
"employeeId"
index
=
"index"
open
=
"("
close
=
")"
separator
=
","
>
#{employeeId}
</
foreach
>
</
if
>
</
where
>
</
select
>
|
Mapper類:
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public
interface
EmployeesMapper {
List<Employees> getEmployeesListParams(List<String> employeeIds);
List<Employees> getEmployeesArrayParams(String[] employeeIds);
List<Employees> getEmployeesMapParams(Map<String,Object> params);
}
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以上所述是小編給大家介紹的MyBatis傳入集合 list 數組 map參數的寫法的全部敘述,希望對大家有所幫助!