Refer the following data service query configuration which contains a sample input parameter of type "ARRAY" which you can effectively use to get your requirement fulfilled.
<query id="setSalaryForEmployeesQuery" useConfig="default">
<sql>update Employees set salary=:salary where employeeNumber in (:employeeNumbers)</sql>
<param name="salary" ordinal="1" paramType="SCALAR" sqlType="DOUBLE" type="IN"/>
<param name="employeeNumbers" ordinal="2" paramType="ARRAY" sqlType="INTEGER" type="IN"/>
</query>
There, if you refer the input mapping configuration named "employeeNumbers", it basically addresses the same requirement mentioned in your query.
To try this functionality, you can use the "tryIt" functionality provided with each data service(similar to other service types) and the data service request format corresponding to the aforementioned configuration would look like what's depicted below.
<p:setSalaryForEmployees xmlns:p="http://ws.wso2.org/dataservice/samples/rdbms_sample">
<!--Exactly 1 occurrence-->
<xs:salary xmlns:xs="http://ws.wso2.org/dataservice/samples/rdbms_sample">1000</xs:salary>
<!--1 or more occurrences-->
<xs:employeeNumbers xmlns:xs="http://ws.wso2.org/dataservice/samples/rdbms_sample">1011</xs:employeeNumbers>
<xs:employeeNumbers xmlns:xs="http://ws.wso2.org/dataservice/samples/rdbms_sample">1022</xs:employeeNumbers>
</p:setSalaryForEmployees>
The complete data service configuration which contains the above configuration snippet can be located in the "DSS_HOME/sample/dbs/rdbms/RDBMSSample.dbs" which resides in DSS product archive.