mule restful proxy throws null pointer exception - pointers

Question

i am building a simple restful proxy using mule. while majority of the rest calls are proxied properly, one of the POST call is throwing a null pointer exception.
Here's the message inbound:
org.mule.DefaultMuleMessage
{
id=c856d080-bd55-11e4-8504-6c40089d7cb6
payload=java.lang.String
correlationId=<not set>
correlationGroup=-1
correlationSeq=-1
encoding=UTF-8
exceptionPayload=<not set>
Message properties:
INVOCATION scoped properties:
INBOUND scoped properties:
accept=text/virl+xml,multipart/mixed
authorization=Basic TmV0U2ltOk5ldFNpbQ==
connection=keep-alive
content-length=1000
content-type=application/xml
host=localhost:9090
http.listener.path=/*
http.method=POST
http.query.params=org.mule.module.http.internal.ParameterMap#330eee18
http.query.string=session=0c603343-49e6-452f-bfdf-1e69cf478f65
http.remote.address=/127.0.0.1:52065
http.request.path=/ank/rest/process
http.request.uri=/ank/rest/process?session=0c603343-49e6-452f-bfdf-1e69cf478f65
http.scheme=http
http.uri.params=org.mule.module.http.internal.ParameterMap#0
http.version=HTTP/1.1
user-agent=Jersey/2.0-rc1 (HttpUrlConnection 1.7.0_71)
OUTBOUND scoped properties:
Content-Type=text/plain;charset=UTF-8
MULE_ENCODING=UTF-8
http.disable.status.code.exception.check=false
SESSION scoped properties:
}
ERROR 2015-02-25 19:21:26,894 [[restproxy].VIRL-UWM-Management-APIs.worker.02] org.mule.exception.CatchMessagingExceptionStrategy:
********************************************************************************
Message : null (java.lang.NullPointerException). Message payload is of type: String
Code : MULE_ERROR--2
--------------------------------------------------------------------------------
Exception stack is:
1. null (java.lang.NullPointerException)
org.mule.module.http.internal.HttpParser:94 (null)
2. null (java.lang.NullPointerException). Message payload is of type: String (org.mule.api.MessagingException)
org.mule.execution.ExceptionToMessagingExceptionExecutionInterceptor:32 (http://www.mulesoft.org/docs/site/current3/apidocs/org/mule/api/MessagingException.html)
--------------------------------------------------------------------------------
Root Exception stack trace:
java.lang.NullPointerException
at org.mule.module.http.internal.HttpParser.parseMultipartContent(HttpParser.java:94)
at org.mule.module.http.internal.request.HttpResponseToMuleEvent.getInboundAttachments(HttpResponseToMuleEvent.java:139)
at org.mule.module.http.internal.request.HttpResponseToMuleEvent.convert(HttpResponseToMuleEvent.java:77)
+ 3 more (set debug level logging or '-Dmule.verbose.exceptions=true' for everything)
********************************************************************************
Have no clue why is it failing. Hitting the actual end point by-passing the proxy works properly. any clues ?
Mule flow:
<?xml version="1.0" encoding="UTF-8"?>
<mule xmlns:tracking="http://www.mulesoft.org/schema/mule/ee/tracking" xmlns:scripting="http://www.mulesoft.org/schema/mule/scripting" xmlns:json="http://www.mulesoft.org/schema/mule/json" xmlns:http="http://www.mulesoft.org/schema/mule/http" xmlns="http://www.mulesoft.org/schema/mule/core" xmlns:doc="http://www.mulesoft.org/schema/mule/documentation"
xmlns:spring="http://www.springframework.org/schema/beans" version="EE-3.6.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-current.xsd
http://www.mulesoft.org/schema/mule/core http://www.mulesoft.org/schema/mule/core/current/mule.xsd
http://www.mulesoft.org/schema/mule/http http://www.mulesoft.org/schema/mule/http/current/mule-http.xsd
http://www.mulesoft.org/schema/mule/json http://www.mulesoft.org/schema/mule/json/current/mule-json.xsd
http://www.mulesoft.org/schema/mule/scripting http://www.mulesoft.org/schema/mule/scripting/current/mule-scripting.xsd
http://www.mulesoft.org/schema/mule/ee/tracking http://www.mulesoft.org/schema/mule/ee/tracking/current/mule-tracking-ee.xsd">
<http:listener-config name="VIRL-UWM-Management-APIs" host="0.0.0.0" port="9090" doc:name="HTTP Listener Configuration"/>
<http:request-config name="Actual-Virl-Enpoint-for-UWM" host="virl03.stic.cisco-services.com" port="19399" doc:name="HTTP Request Configuration"/>
<http:listener-config name="AutoNetKit-API" host="0.0.0.0" port="19401" doc:name="HTTP Listener Configuration"/>
<http:request-config name="AutoNetkit-End-Point" host="virl03.stic.cisco-services.com" port="19401" doc:name="HTTP Request Configuration"/>
<flow name="virl-proxyFlow">
<http:listener config-ref="AutoNetKit-API" path="*" allowedMethods="GET" doc:name="HTTP"/>
<set-property propertyName="http.disable.status.code.exception.check" value="false" doc:name="Disable Exception Check"/>
<logger message=" payload is: #[message.payload], method is: #[message.inboundProperties.'http.method'], Request URI is: #[message.inboundProperties.'http.request.uri'], message is: #[message]" level="INFO" doc:name="Logger"/>
<flow-ref name="copy-headers" doc:name="Copy HTTP Headers"/>
<http:request config-ref="AutoNetkit-End-Point" path="#[message.inboundProperties.'http.request.uri']" method="#[message.inboundProperties.'http.method']" responseTimeout="60000" doc:name="AutoNetKit-EndPoint"/>
<flow-ref name="copy-headers" doc:name="Copy HTTP Headers"/>
</flow>
<flow name="VIRL-Restful-Proxy">
<http:listener config-ref="VIRL-UWM-Management-APIs" path="*" doc:name="HTTP"/>
<choice doc:name="GET-vs-POST">
<when expression="#[message.inboundProperties.'http.method' == 'POST']">
<object-to-string-transformer doc:name="Object to String"/>
<logger message="Set the payload of type string - since it's a post request." level="INFO" doc:name="Logger"/>
</when>
<otherwise>
<logger message="Not setting payload transformation as it's a GET request." level="INFO" doc:name="Logger"/>
</otherwise>
</choice>
<set-property propertyName="http.disable.status.code.exception.check" value="false" doc:name="Disable Exception Check"/>
<logger message=" payload is: #[message.payload], method is: #[message.inboundProperties.'http.method'], Request URI is: #[message.inboundProperties.'http.request.uri'], message is: #[message]" level="INFO" doc:name="Logger"/>
<flow-ref name="copy-headers" doc:name="Copy HTTP Headers"/>
<http:request config-ref="Actual-Virl-Enpoint-for-UWM" path="#[message.inboundProperties.'http.request.uri']"
method="#[message.inboundProperties.'http.method']" responseTimeout="60000" doc:name="VIRL End Point"/>
<logger message="response payload: #[message]" level="INFO" doc:name="Logger"/>
<flow-ref name="copy-headers" doc:name="Copy HTTP Headers"/>
<catch-exception-strategy doc:name="Catch Exception Strategy">
<logger level="DEBUG" message="#[exception.exceptions]" doc:name="Logger"/>
</catch-exception-strategy>
</flow>
<sub-flow name="copy-headers" >
<copy-properties propertyName="*" doc:name="Copy All HTTP Headers"/>
<remove-property propertyName="Content-Length" doc:name="Remove Content Length"/>
<remove-property propertyName="MULE_*" doc:name="Remove MULE Properties"/>
<remove-property propertyName="X_MULE*" doc:name="Remove X_MULE Properties"/>
<remove-property propertyName="X-MULE*" doc:name="Remove X-MULE Properties"/>
</sub-flow>
</mule>
thanks

Answer 1

This is a bug in Mule's code: I've reported it as such, you can track MULE-8342.
In the meantime, you can try the following:
If you have control of the remote server, add a Content-Disposition header in its multipart responses.
Temporarily use an http:outbound-endpoint in lieu of http:request, until the above bug is fixed.