Is there a way to call a transformer method to change the payload in spring integration flow - spring

Question

In the below code I'm transforming the payload to a different payload and sending it as a request body to a POST API call. I want to outsource that transformation through a external method call. Is that possible?
#Bean
public IntegrationFlow flow3(){
return integrationFlowDefinition -> integrationFlowDefinition
.channel(c -> c.executor(Executors.newCachedThreadPool())).log()
// .split("payload.employee")
// .transform(Transformers.toJson()).log()
.transform(Transformers.fromJson(Map.class)).log("json payload to Map object")
.<Map<String, String>, Map<String,String>>transform(
payload -> {
payload.put("name","Somnath Mukhopadhyay");
payload.put("company","xyz");
// payload.put("salary", "20000");
return payload;
}
).log("Modifying the payload")
.transform(Transformers.toJson()).log("modified Map object to JSON")
.enrichHeaders(headerEnricherSpec -> headerEnricherSpec.header("ContentType","application/json"))
.handle(Http.outboundGateway("http://localhost:8888/Employee")
.httpMethod(HttpMethod.POST)
.expectedResponseType(String.class)
)
.log("Getting response back from flow3");
}

Answer 1

There is this one for you:
/**
* Populate the {#code MessageTransformingHandler} for the {#link MethodInvokingTransformer}
* to invoke the service method at runtime.
* #param service the service to use.
* #param methodName the method to invoke.
* #return the current {#link BaseIntegrationFlowDefinition}.
* #see MethodInvokingTransformer
*/
public B transform(Object service, String methodName) {
Read javadocs for those DSL operators.