File gets corrupted when we append data using mule file connector

Question

I'm new to mule soft and I'm trying fetch from salesforce and trying to write it into an excel file. For the first try it works fine, however when I do it again and try to append the the output to the same file my excel file gets corrupted

  <sfdc:config name="Salesforce1" username="*****"
            password="****" securityToken="******"
            doc:name="Salesforce">
            <sfdc:connection-pooling-profile
                initialisationPolicy="INITIALISE_ONE" exhaustedAction="WHEN_EXHAUSTED_GROW" />
        </sfdc:config>
        <data-mapper:config name="contact_to_ms_excel" transformationGraphPath="contact_to_ms_excel.grf" doc:name="contact_to_ms_excel"/>
        <file:connector name="Fileoutput" outputPattern=".xls"  autoDelete="true" outputAppend="true" streaming="true" validateConnections="true" doc:name="File"/>
        <flow name="trial2Flow1" doc:name="trial2Flow1">
            <http:inbound-endpoint exchange-pattern="request-response" host="localhost" port="8081" doc:name="HTTP"/>
            <not-filter doc:name="Not">
                <wildcard-filter pattern="/favicon.ico" caseSensitive="true"/>
            </not-filter>
            <custom-transformer class="Trial" doc:name="Java"/>
            <sfdc:query config-ref="Salesforce1"
                query="select  Phone,Name,Email from Contact WHERE Title ='#[payload]'" doc:name="Salesforce" />
            <data-mapper:transform config-ref="contact_to_ms_excel" doc:name="Contact To MS Excel"/>
            <file:outbound-endpoint path="C:\Users\Suja\exltrial\excel"  responseTimeout="10000" doc:name="File" connector-ref="Fileoutput" outputPattern="Scontact.xls"/>
        </flow>
    </mule> 

Could some one let me know what could be the reason.

Thank you in advance.

Answer 1

You can not append the data from two binary files into a single binary file with an appending file connector. Append the data to a CSV file and then transform that to XLS, or try to find some Java library that can combine two XLS files.