WSO2 Couldn't save JSON payload - esb

Question

I use WSO2 EI 6.6.0 and Micro Integrator 4.0.0. I have an api to get data, but for this I need to authenticate and get a token to use in a further request. for authentication I use separately created api and call it from first flow. For authentication I need to create a payload and send it in the request body to the server, but I get an error. The problem is repeated on different servers and I do not understand what is the reason.
My Auth API looks like this:
<api context="/auth" name="AuthGateway" xmlns="http://ws.apache.org/ns/synapse">
<resource methods="GET" uri-template="/gateway">
<inSequence>
<payloadFactory media-type="json">
<format>{"username": "adm", "password": "admin"}</format>
<args/>
</payloadFactory>
<call>
<endpoint>
<http method="post" uri-template="https://1537-212-90-188-166.ngrok.io/auth/login">
<suspendOnFailure>
<initialDuration>-1</initialDuration>
<progressionFactor>-1</progressionFactor>
<maximumDuration>0</maximumDuration>
</suspendOnFailure>
<markForSuspension>
<retriesBeforeSuspension>0</retriesBeforeSuspension>
</markForSuspension>
</http>
</endpoint>
</call>
<log separator="
">
<property expression="json-eval($)" name="log_auth"/>
</log>
<respond/>
</inSequence>
<outSequence/>
<faultSequence/>
</resource>
My Data API looks like this:
<resource methods="GET" uri-template="/fieldCard?*">
<inSequence>
<propertyGroup>
<property name="uri.var.version" expression="$url:version" scope="default" type="STRING"/>
<property name="uri.var.size" expression="$url:size" scope="default" type="STRING"/>
<property name="uri.var.page" expression="$url:page" scope="default" type="STRING"/>
</propertyGroup>
<log level="full" separator="
">
<property name="version" expression="$ctx:uri.var.version"/>
<property name="size" expression="$ctx:uri.var.size"/>
<property name="page" expression="$ctx:uri.var.page"/>
</log>
<call>
<endpoint>
<http method="GET" uri-template="http://localhost:8290/auth/gateway"/>
</endpoint>
</call> .......
In the console I get messages:
[2022-05-02 19:16:12,962] ERROR {JsonStreamBuilder} - Error occurred while processing document for application/json java.lang.reflect.InvocationTargetException
Caused by: org.apache.axis2.AxisFault: #Can not parse stream. MessageID: urn:uuid:7ac6a4c9-0ed1-4973-87d4-69dad6d4a950. Error>>> #getNewJsonPayload. Could not save JSON payload. Invalid input stream found. Payload is not a JSON string.
org.apache.synapse.commons.json.JsonStreamBuilder.processDocument(JsonStreamBuilder.java:43)
... 21 more
Caused by: org.apache.axis2.AxisFault: #getNewJsonPayload. Could not save JSON payload. Invalid input stream found. Payload is not a JSON string.
[2022-05-02 19:16:12,963] ERROR {DeferredMessageBuilder} - Error building message org.apache.axis2.AxisFault
[2022-05-02 19:16:12,964] ERROR {RelayUtils} - Error while building Passthrough stream org.apache.axis2.AxisFault
[2022-05-02 19:16:12,964] ERROR {SequenceMediator} - {api:AuthGateway} Error while building message. Error while building Passthrough stream org.apache.axis2.AxisFault: Error while building Passthrough stream
I removed the detailed stack trace. If it is needed to understand the problem - I can add it.
P.S. When calling the auth API directly I get the token and the response is correct.
[2022-05-02 19:20:17,560] INFO {org.apache.synapse.mediators.builtin.LogMediator} - To: http://www.w3.org/2005/08/addressing/anonymous
WSAction:
SOAPAction:
MessageID: urn:uuid:817185a7-39a4-4418-a696-72473672997d
Direction: request
log_auth = {"access_token":"eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9.eyJ1c2VyX2lkIjoiMyIsInVzZXJfbmFtZSI6Im...
Payload: {"access_token":"eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9.eyJ1c2VyX2lkIjoiMyIsInVzZXJfbmFtZSI6Im...
Please help me understand the problem.
UPD: I reinstalled the server because I thought the error might be there or I broke the config files. created a new project and wrote a new same thread, but the error still repeats.

Answer 1

Good. The problem was that Postman has a Header Accept-Encoding option. When this parameter was disabled, the request became correct and the response began to come without errors!