[WSO2 ESB][4.9.0] NPE on iterate when sending back - nullpointerexception

Question

Newbie on WSO2 ESB, we start using it as our central point as ESB but we are facing a real issue by doing a simple case :/
Here is the api I wrote (based on that simple) to show you my issue even if our usecase is different.
Users
<?xml version="1.0" encoding="UTF-8" ?>
<api context="/services/users" name="ListUsersAPI" xmlns="http://ws.apache.org/ns/synapse">
<resource methods="GET" protocol="http" url-mapping="/*">
<inSequence>
<payloadFactory media-type="json">
<format>{ "persons":{ "person":[ { "Id":"1", "givenName":"ajith", "lastName":"vitharana", "age":"25", "contactInfos":[ { "InfoId":"1", "department":"1", "contactType":"email", "value":"ajith#abc.org" }, { "InfoId":"2", "department":"1", "contactType":"mobile",
"value":"111111111" }, { "InfoId":"3", "department":"1", "contactType":"home", "value":"Magic Dr,USA" } ] }, { "Id":"2", "givenName":"shammi", "lastName":"jagasingha", "age":"30", "contactInfos":[ { "InfoId":"1", "department":"1", "contactType":"email",
"value":"shammi#abc.org" }, { "InfoId":"2", "department":"1", "contactType":"mobile", "value":"2222222222" }, { "InfoId":"3", "department":"1", "contactType":"home", "value":"Magic Dr,USA" } ] } ] }}</format>
<args/>
</payloadFactory>
<property action="remove" name="NO_ENTITY_BODY" scope="axis2" />
<property name="messageType" scope="axis2" type="STRING" value="application/json" />
<respond/>
</inSequence>
<outSequence/>
<faultSequence/>
</resource>
</api>
Roles
<?xml version="1.0" encoding="UTF-8" ?>
<api context="/services/roles" name="UserRolesAPI" xmlns="http://ws.apache.org/ns/synapse">
<resource methods="GET" protocol="http" uri-template="/{personid}">
<inSequence>
<filter regex="1" source="get-property('uri.var.personid')">
<then>
<payloadFactory media-type="json">
<format>{ "Id":1, "roles":[ { "roleId":1, "personKey":1, "role":"Deverloper" }, { "roleId":2, "personKey":1, "role":"Engineer" } ]}</format>
<args/>
</payloadFactory>
<property action="remove" name="NO_ENTITY_BODY" scope="axis2" />
<property name="messageType" scope="axis2" type="STRING" value="application/json" />
<respond/>
</then>
<else/>
</filter>
<filter regex="2" source="get-property('uri.var.personid')">
<then>
<payloadFactory media-type="json">
<format>{"personId": 2,"roles": [{ "personRoleId": 1, "personKey": 2, "role": "Manager" },{ "personRoleId": 2, "personKey": 2, "role": "QA" }]}</format>
<args/>
</payloadFactory>
<property action="remove" name="NO_ENTITY_BODY" scope="axis2" />
<property name="messageType" scope="axis2" type="STRING" value="application/json" />
<respond/>
</then>
<else/>
</filter>
</inSequence>
<outSequence/>
<faultSequence/>
</resource>
</api>
Finally, the main one, calling the first one, then iterating
<?xml version="1.0" encoding="UTF-8" ?>
<api context="/userdetails" name="UserDetailsAPI" xmlns="http://ws.apache.org/ns/synapse">
<resource methods="GET" protocol="http">
<inSequence>
<call>
<endpoint>
<http method="get" trace="disable" uri-template="http://localhost:8280/services/users" />
</endpoint>
</call>
<iterate attachPath="//jsonObject/persons" expression="//jsonObject/persons/person" id="it1" preservePayload="true" xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/">
<target>
<sequence>
<property expression="$body/jsonObject/persons/person/Id" name="uri.var.Id" scope="default" type="STRING" xmlns:ns="http://org.apache.synapse/xsd" />
<property expression="$body//jsonObject//person" name="response1" scope="default" type="STRING" xmlns:ns="http://org.apache.synapse/xsd" />
<call>
<endpoint>
<http method="get" trace="disable" uri-template="http://localhost:8280/services/roles/{uri.var.Id}" />
</endpoint>
</call>
<loopback/>
</sequence>
</target>
</iterate>
</inSequence>
<outSequence>
<send/>
</outSequence>
<faultSequence>
<sequence key="fault" />
</faultSequence>
</resource>
</api>
Executing the last api (http://localhost:8280/userdetails) is causing the following NPE:
20160408T101619.566 org.apache.synapse.transport.passthru.PassThroughHttpSender.handleException(PassThroughHttpSender.java:609) [PassThroughMessageProcessor-14] PassThroughHttpSender - Failed to submit the response
java.lang.NullPointerException
at org.apache.synapse.transport.passthru.util.SourceResponseFactory.create(SourceResponseFactory.java:64)
at org.apache.synapse.transport.passthru.PassThroughHttpSender.submitResponse(PassThroughHttpSender.java:462)
at org.apache.synapse.transport.passthru.PassThroughHttpSender.invoke(PassThroughHttpSender.java:267)
at org.apache.axis2.engine.AxisEngine.send(AxisEngine.java:442)
at org.apache.synapse.core.axis2.Axis2Sender.sendBack(Axis2Sender.java:212)
at org.apache.synapse.core.axis2.Axis2SynapseEnvironment.send(Axis2SynapseEnvironment.java:444)
at org.apache.synapse.mediators.builtin.SendMediator.mediate(SendMediator.java:102)
at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:81)
at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:48)
at org.apache.synapse.mediators.base.SequenceMediator.mediate(SequenceMediator.java:149)
at org.apache.synapse.rest.Resource.process(Resource.java:297)
at org.apache.synapse.rest.API.process(API.java:335)
at org.apache.synapse.rest.RESTRequestHandler.dispatchToAPI(RESTRequestHandler.java:97)
at org.apache.synapse.rest.RESTRequestHandler.process(RESTRequestHandler.java:52)
at org.apache.synapse.core.axis2.Axis2SynapseEnvironment.injectMessage(Axis2SynapseEnvironment.java:266)
at org.apache.synapse.mediators.builtin.LoopBackMediator.mediate(LoopBackMediator.java:55)
at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:81)
at org.apache.synapse.mediators.eip.splitter.IterateMediator.mediate(IterateMediator.java:241)
at org.apache.synapse.mediators.base.SequenceMediator.mediate(SequenceMediator.java:267)
at org.apache.synapse.core.axis2.Axis2SynapseEnvironment.mediateFromContinuationStateStack(Axis2SynapseEnvironment.java:679)
at org.apache.synapse.core.axis2.Axis2SynapseEnvironment.injectMessage(Axis2SynapseEnvironment.java:244)
at org.apache.synapse.core.axis2.SynapseCallbackReceiver.handleMessage(SynapseCallbackReceiver.java:529)
at org.apache.synapse.core.axis2.SynapseCallbackReceiver.receive(SynapseCallbackReceiver.java:172)
at org.apache.axis2.engine.AxisEngine.receive(AxisEngine.java:180)
at org.apache.synapse.transport.passthru.ClientWorker.run(ClientWorker.java:251)
at org.apache.axis2.transport.base.threads.NativeWorkerPool$1.run(NativeWorkerPool.java:172)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
20160408T101619.576 org.apache.synapse.core.axis2.Axis2Sender.handleException(Axis2Sender.java:246) [PassThroughMessageProcessor-14] Axis2Sender - Accept:*/*,Accept-Encoding:gzip, deflate, sdch,Accept-Language:fr-FR,fr;q=0.8,en-US;q=0.6,en;q=0.4,Cache-Control:no-cache,Content-Type:application/json; charset=UTF-8,Host:localhost:8280,Postman-Token:3bfb96b7-0c31-964e-8c37-3b5dbd222efe,<?xml version='1.0' encoding='utf-8'?><soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"><soapenv:Body><jsonObject><Id>1</Id><roles><roleId>1</roleId><personKey>1</personKey><role>Deverloper</role></roles><roles><roleId>2</roleId><personKey>1</personKey><role>Engineer</role></roles></jsonObject></soapenv:Body></soapenv:Envelope> Unexpected error sending message back
org.apache.axis2.AxisFault: Failed to submit the response
at org.apache.synapse.transport.passthru.PassThroughHttpSender.handleException(PassThroughHttpSender.java:610)
at org.apache.synapse.transport.passthru.PassThroughHttpSender.invoke(PassThroughHttpSender.java:269)
at org.apache.axis2.engine.AxisEngine.send(AxisEngine.java:442)
at org.apache.synapse.core.axis2.Axis2Sender.sendBack(Axis2Sender.java:212)
at org.apache.synapse.core.axis2.Axis2SynapseEnvironment.send(Axis2SynapseEnvironment.java:444)
at org.apache.synapse.mediators.builtin.SendMediator.mediate(SendMediator.java:102)
at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:81)
at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:48)
at org.apache.synapse.mediators.base.SequenceMediator.mediate(SequenceMediator.java:149)
at org.apache.synapse.rest.Resource.process(Resource.java:297)
at org.apache.synapse.rest.API.process(API.java:335)
at org.apache.synapse.rest.RESTRequestHandler.dispatchToAPI(RESTRequestHandler.java:97)
at org.apache.synapse.rest.RESTRequestHandler.process(RESTRequestHandler.java:52)
at org.apache.synapse.core.axis2.Axis2SynapseEnvironment.injectMessage(Axis2SynapseEnvironment.java:266)
at org.apache.synapse.mediators.builtin.LoopBackMediator.mediate(LoopBackMediator.java:55)
at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:81)
at org.apache.synapse.mediators.eip.splitter.IterateMediator.mediate(IterateMediator.java:241)
at org.apache.synapse.mediators.base.SequenceMediator.mediate(SequenceMediator.java:267)
at org.apache.synapse.core.axis2.Axis2SynapseEnvironment.mediateFromContinuationStateStack(Axis2SynapseEnvironment.java:679)
at org.apache.synapse.core.axis2.Axis2SynapseEnvironment.injectMessage(Axis2SynapseEnvironment.java:244)
at org.apache.synapse.core.axis2.SynapseCallbackReceiver.handleMessage(SynapseCallbackReceiver.java:529)
at org.apache.synapse.core.axis2.SynapseCallbackReceiver.receive(SynapseCallbackReceiver.java:172)
at org.apache.axis2.engine.AxisEngine.receive(AxisEngine.java:180)
at org.apache.synapse.transport.passthru.ClientWorker.run(ClientWorker.java:251)
at org.apache.axis2.transport.base.threads.NativeWorkerPool$1.run(NativeWorkerPool.java:172)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.NullPointerException
at org.apache.synapse.transport.passthru.util.SourceResponseFactory.create(SourceResponseFactory.java:64)
at org.apache.synapse.transport.passthru.PassThroughHttpSender.submitResponse(PassThroughHttpSender.java:462)
at org.apache.synapse.transport.passthru.PassThroughHttpSender.invoke(PassThroughHttpSender.java:267)
... 26 more
I'm afraid, this is the same issue than here (but not sure).
Would you please help me quickly to avoid before we decide to give wso2 away ?
The better would be to have the third part (userdetails) fixed by an answer.
Thank a lot !

Answer 1

In this case your loopback is inside the iterate mediator and that is calling outSequence each time you iterate.
If you move your loopback mediator out of the iterate as shown below, this should send the last response from the iterate to the client. If you want to aggregate your responses from the iteration, you should use aggregate mediator[1].
[1] https://docs.wso2.com/display/ESB490/Aggregate+Mediator
Updated
Unfortunately the above solution does not work, because each time an iteration completes, the flow still continues, so even if we have a loopback outside the iterate, we will be calling the outSequence multiple times. We will have to use an aggregate to be able to use the complete condition to trigger the outSequence once. Please have a look at the below configuration.
<api xmlns="http://ws.apache.org/ns/synapse" name="UserDetailsAPI" context="/userdetails">
<resource methods="GET">
<inSequence>
<call>
<endpoint>
<http trace="disable" method="GET" uri-template="http://localhost:8280/services/users"/>
</endpoint>
</call>
<iterate xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" id="it1" preservePayload="true" attachPath="//jsonObject/persons" expression="//jsonObject/persons/person">
<target>
<sequence>
<property xmlns:ns="http://org.apache.synapse/xsd" name="uri.var.Id" expression="$body/jsonObject/persons/person/Id" scope="default" type="STRING"/>
<property xmlns:ns="http://org.apache.synapse/xsd" name="response1" expression="$body//jsonObject//person" scope="default" type="STRING"/>
<call>
<endpoint>
<http trace="disable" method="GET" uri-template="http://localhost:8280/services/roles/{uri.var.Id}"/>
</endpoint>
</call>
</sequence>
</target>
</iterate>
<aggregate id="it1">
<completeCondition>
<messageCount min="-1" max="-1"/>
</completeCondition>
<onComplete expression="//jsonObject">
<loopback/>
</onComplete>
</aggregate>
</inSequence>
<outSequence>
<send/>
</outSequence>
<faultSequence>
<sequence key="fault"/>
</faultSequence>
</resource>
</api>