Spring integration tcp outbound and http inbound don t work properly - json

Question

Hey I am sitting in front of Spring Integration for several days without speedy progress. Hope you can help me:
My trace:
Client.Input (POJO)
-> Client.[tcp-outbound].defaultserializer
-> Server.[tcp-inbound].defaultserializer
-> Server.[http-outbound] -> transform(POJO-to-Json)
-> Spring MVC Controller : return same POJO (automatic transform to json)
-> Server -> transform(Json-to-POJO)
-> Server -> defaultserializer
-> Client -> defaultserializer
Here the configuration:
Client-Side:
<int:channel id="input" />
<int-ip:tcp-connection-factory id="client"
type="client"
host="192.168.178.28"
port="5678"
serializer="javaSerializer"
deserializer="javaDeserializer"/>
<int-ip:tcp-outbound-gateway id="outboundGateway"
request-channel="input"
connection-factory="client"
request-timeout="10000"
reply-timeout="10000"/>
Server-Side:
<int-ip:tcp-connection-factory id="connectionFactory"
type="server"
port="6000"
serializer="javaSerializer"
deserializer="javaDeserializer"/>
<int-ip:tcp-inbound-gateway id="inboundGateway"
connection-factory="connectionFactory"
request-channel="requestChannel"
reply-channel="outboundChannel"/>
<int:channel id="requestChannel" />
<int:channel id="toMvcChannel" />
<int:channel id="toTcpChannel" />
<int:channel id="outboundChannel" />
<int:object-to-json-transformer input-channel="requestChannel"
output-channel="toMvcChannel"/>
<int:header-enricher input-channel="toMvcChannel">
<int:header name="Content-Type" value="application/json" />
</int:header-enricher>
<int-http:outbound-gateway
url="http://localhost:10100/arx/dataset/receiveGateway"
request-channel="toMvcChannel"
reply-channel="toTcpChannel"/>
<int:json-to-object-transformer input-channel="toTcpChannel"
output-channel="outboundChannel"/>
SimpleGateway:
public interface SimpleGateway {
public DefinitionServer send(DefinitionServer definition);}
I cannot understand why I get the error message below on Client side ON RECEIVE (last step in the routing):
No converter found capable of converting from type [java.lang.String] to type [...DefinitionServer]
Thanks in advance!