Spring Integration DSL transformer - spring-integration

Question

Can I have some help here on the below issue:
Calling the transformer to transform the input object to Map Object and calling handler, the handler is missing header values added before.
Why on transforming payload to Map object losing all headers?
//Adding header here setHeader("t", "t");
#ResponseBody
public EmResponse getAuditTrail(#Valid #RequestBody NGAuditTrailEntry auditEntry) {
LOG.info("Audit Service Called, creating new audit " + auditEntry);
AuditCreationFlow.CreateAuditGateway auditGateway = applicationContext.getBean(AuditCreationFlow.CreateAuditGateway.class);
MessageBuilder messageBuilder = MessageBuilder.withPayload(auditEntry).setHeader("t", "t");
Object response = auditGateway.createAudit(messageBuilder.build());
EmResponse res = new EmResponse();
LOG.info("Done with Audit creation. Response " + response);
return res;
}
//Integration flow starts here
public IntegrationFlow createAuditGatewayFlow() {
LOG.debug("Entered to spring integration flow to create the Audit entry");
return IntegrationFlows.from("auditInputChannel")
.handle(auditObjTransformer, "transformToEjbCompatible")
.handle(ejbCaller, "callEjb")
.get();
}
//Transforming payload object to map
#Component
public class AuditObjTransformer {
private final Logger LOG = LoggerFactory.getLogger(this.getClass());
#Transformer
public Object transformToEjbCompatible(NGAuditTrailEntry ngAuditTrailEntry, Map<String, Object> headers) {
LOG.debug("Transforming the NGAuditTrailEntry To AuditEntry object which is EJB compatible");
//#TODO - Tranformation code goes here.
String s = ngAuditTrailEntry.getObjectName();
Map<String, String> m = new HashMap<>();
m.put("x", s);
return m;
}
//Here in this handler, not getting headers what I added in the rest service above.
public class EJBCaller {
private final Logger LOG = LoggerFactory.getLogger(this.getClass());
public Object callEjb(Object payload, Map<String, Object> headers) throws EJBResponseException {
LOG.debug("Calling Audit EJB to crated Audit entry.");
//#TODO EJB calling code goese here.
LOG.debug("Returned from EJB after creating Audit entry. Returned value" + payload);
return payload;
}
If the transform is other than map then no issues in headers.
Thanks,
Siva

Answer 1

callEjb(Object payload, Map<String, Object> headers)
If payload is a Map, you have that payload in the payload and the headers method arguments at the same time.
To make it working and carry exactly headers to that Map argument you should use #Headers annotation on it:
* Annotation which indicates that a method parameter should be bound to the headers of a
* message. The annotated parameter must be assignable to {#link java.util.Map} with
* String keys and Object values.