WSO2 ESB aggregate mediator not working properly - xpath

Question

i m using the wso2ESB 4.8.0 and i followed the sample at this url:
https://docs.wso2.org/display/ESB480/Sample+62:+Routing+a+Message+to+a+Dynamic+List+of+Recipients+and+Aggregating+Responses
writing this proxy service:
<?xml version="1.0" encoding="UTF-8"?>
<proxy xmlns="http://ws.apache.org/ns/synapse"
name="adminBroadcastEndpoint"
transports="https,http"
statistics="disable"
trace="disable"
startOnLoad="true">
<target>
<inSequence>
<send>
<endpoint>
<recipientlist>
<endpoint>
<address uri="http://127.0.0.1:8080/RestService/rest/servizio/"/>
</endpoint>
<endpoint>
<address uri="http://127.0.0.1:8081/RestService/rest/servizio/"/>
</endpoint>
</recipientlist>
</endpoint>
</send>
<drop/>
</inSequence>
<outSequence>
<payloadFactory media-type="xml">
<format>
<broadcast>
$1
</broadcast>
</format>
<args>
<arg evaluator="xml" expression="$body/root"/>
</args>
</payloadFactory>
<aggregate>
<completeCondition>
<messageCount/>
</completeCondition>
<onComplete xmlns:soapenv="http://www.w3.org/2003/05/soap-envelope" expression="/">
<send/>
</onComplete>
</aggregate>
</outSequence>
</target>
<description/>
</proxy>
in the recipient list there are two servers who answer with an xml string. The first server answer with
<root>
<codice>0</codice>
<messaggio>MESSAGE1</messaggio>
<result><name>CorreggiPecJob1</name><group>POSTA1</group></result>
<result><name>SchedulaIndiceJob1</name><group>INDICE1</group></result>
</root>
and the second server with:
<root>
<codice>0</codice>
<messaggio>MESSAGE2</messaggio>
<result><name>CorreggiPecJob2</name><group>POSTA2</group></result>
<result><name>SchedulaIndiceJob2</name><group>INDICE2</group></result>
</root>
After the aggregate mediator i should expect a result with all those 2 message merged... but in the response from the proxy service i get just the second server answer or the first one randomly.
If i put a log mediator suddenly after the onComplete tag hawever i the esb prints the whole merged message with the two response, but it seems that on the send mediator something goes lost.
Why does this happen?
Another question is: why xpath expressions like
$body/broadcast//result
don't work rising this exception?
2014-03-02 17:37:32,021] ERROR - AggregateMediator Error evaluating expression: $body/broadcast//result
org.apache.synapse.SynapseException: Could not find matching elements to aggregate.
I realize that if i define a namespace and a prfix to append in the payloadfactory like:
<payloadFactory xmlns:m0="my.namespace" media-type="xml">
<m0:format>
<m0:broadcast>
$1
</m0:broadcast>
</m0:format>
<args>
<arg evaluator="xml" expression="$body/root"/>
</args>
</payloadFactory>
the expression: $body/m0:broadcast work fine... so is it the namespace definition mandatory?
Is it there anything i'm missing? thanks

Answer 1

If the XML elements are in namespaces, than you're XPath must either define and use namespace prefixes, or specify any namespace in the path steps, like this:
$body/*:broadcast

Answer 2

i found the answer here: wso2 ESB : Split / Gather Pattern - Single Response
i solved using the enrich mediator. But i think that the aggregate mediator has not a really correct behaviour... maybe should be checked.