WSO2 ESB - sending unwanted empty JSON payload when passing through tier from backend

Question

I am very new to WSO2 development so this could be an easy fix for someone!

I'm creating a demo API to familiarise myself more with WSO2 development. I'm currently stuck with passing a payload in ESB from a back-end (mocked using Wiremock) to another endpoint. I can see in the ESB logs that the payload is coming into ESB but it leaves as 0 or what I presume as empty.

Is there anything extra I should add? I'm just placing a send mediator within a switch statement (checking for HTTP status eg 200). I've played around with a payloadFactory but it does the same.

ESB log:

TID: [0] [ESB] [2018-03-28 15:56:48,652] DEBUG {org.apache.synapse.transport.http.wire} -  >> "[\r][\n]" {org.apache.synapse.transport.http.wire}
TID: [0] [ESB] [2018-03-28 15:56:48,652] DEBUG {org.apache.synapse.transport.http.wire} -  >> "{"result": 1}" {org.apache.synapse.transport.http.wire}
TID: [0] [ESB] [2018-03-28 15:56:48,699] DEBUG {org.apache.synapse.transport.http.wire} -  << "HTTP/1.1 200 OK[\r][\n]" {org.apache.synapse.transport.http.wire}
TID: [0] [ESB] [2018-03-28 15:56:48,700] DEBUG {org.apache.synapse.transport.http.wire} -  << "CorrelationId: 685454f5-e5f6-4837-b0b0-1e9e53798ea9[\r][\n]" {org.apache.synapse.transport.http.wire}
TID: [0] [ESB] [2018-03-28 15:56:48,700] DEBUG {org.apache.synapse.transport.http.wire} -  << "Content-Type: application/json[\r][\n]" {org.apache.synapse.transport.http.wire}
TID: [0] [ESB] [2018-03-28 15:56:48,700] DEBUG {org.apache.synapse.transport.http.wire} -  << "Date: Wed, 28 Mar 2018 14:56:48 GMT[\r][\n]" {org.apache.synapse.transport.http.wire}
TID: [0] [ESB] [2018-03-28 15:56:48,700] DEBUG {org.apache.synapse.transport.http.wire} -  << "Server: WSO2-PassThrough-HTTP[\r][\n]" {org.apache.synapse.transport.http.wire}
TID: [0] [ESB] [2018-03-28 15:56:48,700] DEBUG {org.apache.synapse.transport.http.wire} -  << "Transfer-Encoding: chunked[\r][\n]" {org.apache.synapse.transport.http.wire}
TID: [0] [ESB] [2018-03-28 15:56:48,700] DEBUG {org.apache.synapse.transport.http.wire} -  << "Connection: Keep-Alive[\r][\n]" {org.apache.synapse.transport.http.wire}
TID: [0] [ESB] [2018-03-28 15:56:48,700] DEBUG {org.apache.synapse.transport.http.wire} -  << "[\r][\n]" {org.apache.synapse.transport.http.wire}
TID: [0] [ESB] [2018-03-28 15:56:48,701] DEBUG {org.apache.synapse.transport.http.wire} -  << "0[\r][\n]" {org.apache.synapse.transport.http.wire}
TID: [0] [ESB] [2018-03-28 15:56:48,701] DEBUG {org.apache.synapse.transport.http.wire} -  << "[\r][\n]" {org.apache.synapse.transport.http.wire}

JSON Payload sent from wiremock to ESB:

{"result": 1}

I played around with using a payloadFactory but I got the same result regardless. I'll include the payloadFactory code I used if it helps:

<payloadFactory media-type="json">
<format>{"amount": $1}</format>
<args>
<arg evaluator="json" expression="$.result"/>
</args>
</payloadFactory>
<property name="messageType" value="application/json" scope="axis2"/>
<property name="contentType" value="application/json" scope="axis2"/>

Any help to solving this or things to try will be much appreciated!

Answer 1

尝试使用<arg evaluator="Xml" expression="//*[local-name()='result']"/>而不是<arg evaluator="json" expression="$.result"/>

Answer 2

I solved this in the end. Turned out to be a conflict between message builders in my axis2.xml properties so the message was never getting built correctly. Thanks for the suggestions anyway!