The expression does not evaluate to a type that can be split: java.lang.String

Hi, I am doing simple Mule flow. Reading xml file from file connector and using the Splitter I am dividing the message and writing into different path. Mule Flow: <flow name="write-xml-file-to-pathFlow1">
<file:inbound-endpoint path="./src/main/resources/in" connector-ref="File" responseTimeout="10000" doc:name="File" pollingFrequency="5000" moveToDirectory="./src/main/resources/out"> <file:filename-regex-filter pattern="product.xml" caseSensitive="true"/> </file:inbound-endpoint> <splitter expression="#[xpath3('//product')]" doc:name="Splitter"/> <mulexml:dom-to-xml-transformer doc:name="DOM to XML"/> <file:outbound-endpoint path="./src/main/resources/out" connector-ref="File1" responseTimeout="10000" doc:name="File"/> <logger message="#[payload]" level="INFO" doc:name="Logger"/>

</flow>

And the xml file is:

<Products>

<product>

     <pid>m1</pid>
     <pmodel>mbm1</pmodel>
     <pname>mobile</pname>
     <price>6000.0</price>
     <stock>20</stock>
 </product>
 <product>
     <pid>m2</pid>
     <pmodel>mbm2</pmodel>
     <pname>mobile</pname>
     <price>8000.0</price>
     <stock>10</stock>
 </product>