How to Remove charset=utf-8 in WSO2 ESB - wso2

Question

I have a requirement to call rest service, which accept "Content-Type: application/json" in header but when I try to call it from ESB. WSO2 adds "charset=utf-8" automatically. I am not sure how to remove it.
I have also used ContentType property but no luck.
<property name="HTTP_METHOD" scope="axis2" type="STRING" value="PUT"/>
<property name="ContentType" scope="axis2" type="STRING" value="application/json"/>
<header expression="fn:concat('Basic ', get-property('ENCODED_URL'))" name="Authorization" scope="transport" xmlns:ns="http://org.apache.synapse/xsd"/>
<payloadFactory media-type="json">
<format>{
"name": "XXX_Token",
"type": "XXXX-cf04186e2156_sessionID",
"version": "1.0.1",
"Attribute-N": $1
}
</format>
<args>
<arg expression="$ctx:XXXTokenValue" literal="false" />
</args>
</payloadFactory>
<property name="REST_URL_POSTFIX" scope="axis2" value=""/>
<call>
<endpoint>
<address trace="disable" uri="https://XXXXX:9493/governance/restservices/52b1caba-b507-4f6a-95bc-2ea7b2418e67"/>
</endpoint>
</call>
Logs:
- End : Call mediator - Non Blocking Call
TID: [-1] [ESB] [2017-09-21 14:30:37,785] DEBUG {org.apache.synapse.transport.http.wire} - << "PUT /governance/restservices/5XXXXX2ea7b2418e67 HTTP/1.1[\r][\n]"
TID: [-1] [ESB] [2017-09-21 14:30:37,785] DEBUG {org.apache.synapse.transport.http.wire} - << "X-AspNet-Version: 4.0.30319[\r][\n]"
TID: [-1] [ESB] [2017-09-21 14:30:37,785] DEBUG {org.apache.synapse.transport.http.wire} - << "Authorization: Basic YWRtaW46YWRtaW4=[\r][\n]"
TID: [-1] [ESB] [2017-09-21 14:30:37,785] DEBUG {org.apache.synapse.transport.http.wire} - << "Content-Type: application/json; charset=utf-8[\r][\n]"
TID: [-1] [ESB] [2017-09-21 14:30:37,785] DEBUG {org.apache.synapse.transport.http.wire} - << "X-Powered-By: ASP.NET[\r][\n]"
TID: [-1] [ESB] [2017-09-21 14:30:37,785] DEBUG {org.apache.synapse.transport.http.wire} - << "Cache-Control: private, max-age=0[\r][\n]"
TID: [-1] [ESB] [2017-09-21 14:30:37,785] DEBUG {org.apache.synapse.transport.http.wire} - << "Transfer-Encoding: chunked[\r][\n]"
TID: [-1] [ESB] [2017-09-21 14:30:37,785] DEBUG {org.apache.synapse.transport.http.wire} - << "Host: XXXXXXz:9493[\r][\n]"
TID: [-1] [ESB] [2017-09-21 14:30:37,785] DEBUG {org.apache.synapse.transport.http.wire} - << "Connection: K

Answer 1

This was a bug in ESB 4.9.0 [1]. This might have fixed in later versions.
Please check whether below property is available in "/repository/conf/passthru-http.properties"
http.headers.preserve=Content-Type
(Note that you can add multiple header values as comma separated list)
Btw use the property "messageType" to set the Content type. Please refer the document on messageType and ContentType from [2]
[1] https://wso2.org/jira/browse/ESBJAVA-4620
[2] https://docs.wso2.com/display/ESB500/Generic+Properties#GenericProperties-messageType