How to save file data present in transport vfs to a parameter in WSO2?

I want to pass the csv file data present in local drive as a string parameter to the DB query. How do I save the file data from vfs to a parameter property?

Also, this is a polling process and hence want to make use of transport vfs if it is possible. Not file connector.

<proxy name="CSVFileProcessorPostDemo" startOnLoad="true" transports="http https vfs" xmlns="http://ws.apache.org/ns/synapse">
    <target>
        <inSequence>
            <dblookup>
                <connection>
                    <pool>
                        <driver>org.postgresql.Driver</driver>
                        <url>jdbc:postgresql://**************/**********</url>
                        <user>*********</user>
                        <password>*********</password>
                    </pool>
                </connection>
                <statement>
                    <sql><![CDATA[SELECT * FROM ba_ior_integration.fn_transform_ior_msg_to_idoc(?)]]></sql>
                    <parameter type="VARCHAR" value="{How to read the transport file data?}"/>
                    <result column="1" name="output_db_idoc"/>
                </statement>
            </dblookup>
            <property expression="get-property('output_db_idoc')" name="dbOutput" scope="default" type="STRING" xmlns:ns="http://org.apache.synapse/xsd" xmlns:ns3="http://org.apache.synapse/xsd"/>

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   <parameter name="transport.PollInterval">5</parameter>
    <parameter name="transport.vfs.FileURI">file://D:\ESB\files\input_IOR_files</parameter>
    <parameter name="transport.vfs.ContentType">text/plain</parameter>
    <parameter name="transport.vfs.ActionAfterProcess">MOVE</parameter>
    <parameter name="transport.vfs.MoveAfterFailure">file://D:\ESB\files\failure_IOR_files</parameter>
    <parameter name="transport.vfs.ActionAfterFailure">MOVE</parameter>
    <parameter name="transport.vfs.Append">true</parameter>
    <parameter name="transport.vfs.FileNamePattern">.*.csv</parameter>
    <parameter name="transport.vfs.MoveAfterProcess">file://D:\ESB\files\output_IOR_files</parameter>
</proxy>

Solution

Have searched and found two ways of handling it.

1) It is simply present under $ctx.body tag.

 <property expression="$body//m0:text" name="dbInput" scope="default"
 type="STRING" xmlns:m0="http://ws.apache.org/commons/ns/payload"/>

And then in dbLookup:

 <sql><![CDATA[SELECT * FROM abcde.fn_transform_xyz_msg_to_idoc(?)]]></sql>
                    <parameter expression="synapse:get-property('dbInput')" type="VARCHAR"/>
                    <result column="1" name="output_db_idoc"/>

2) Using Java class mediator. The message string is present in MessageContext object.

context.getMessageString() provides the SoapEnvelope required, using which the required inner text can be extracted.

context.getSOAPEnvelop(): This did not work for me, shall look into it.

The takeaway is that the data of the files considered under vfs are all present sequentially under MessageContext.