I am new to Jbpm

I have created a workflow in JBPM with business flow having rules and Human task . The workflow accepts a process variable which is a customer object ( Class name Quote) . If I start the workflow using Kie Workbech ,it works fine but when I am trying to start the process from REST API of the Client API , is sends me error as

" "Unexpected HTTP response code when requesting URI

'http://localhost:8080/kie-server/services/rest/server/containers/QuoteManagedRules_1.0.0-SNAPSHOT/processes/QuoteManagedRules.quoteManagedRules/instances'!

Error code: 500, message: \"Unable to create response: [QuoteManagedRules.quoteManagedRules:181 - Quote received:7] -- java.util.LinkedHashMap cannot be cast to com.myspace.quotemanagedrules.QuoteDto\"","

I have tried debugging and turn out that instead of a custom object , if I using String or any other literals it works fine but with the process variable as an Object , it shows error

public static final String SERVER_URL="http://localhost:8080/kie-server/services/rest/server"; 
public static final String LOGIN="wbadmin"; 
public static final String PASSWORD="wbadmin"; 
public static final String CONTAINER="QuoteManagedRules_1.0.0-SNAPSHOT"; 
public static final String processId="QuoteManagedRules.quoteManagedRules"; 
public static void startProcess() 

{  //Client configuration setup 

KieServicesConfiguration config = KieServicesFactory.newRestConfiguration(SERVER_URL, LOGIN, PASSWORD);  

//Add custom classes, such as Obj.class, to the configuration 

Set<Class<?>> extraClassList = new HashSet<Class<?>>(); 

extraClassList.add(QuoteDto.class);
config.addExtraClasses(extraClassList); 
config.setMarshallingFormat(MarshallingFormat.JSON); 

 // ProcessServicesClient setup 
KieServicesClient client = KieServicesFactory.newKieServicesClient(config); 
ProcessServicesClient processServicesClient = client.getServicesClient(ProcessServicesClient.class); 

 // Create an instance of the custom class 
QuoteDto obj = new QuoteDto(); 
obj.setAccountId("1"); 
obj.setCorrelationId("1"); 
obj.setId("12"); 
obj.setOppurtunityId("123"); 
obj.setOppurtunityName("sattu");
obj.setPrice(123); 
obj.setRevision(12);
obj.setVersion("12"); 
Map<String, Object> variables   = new HashMap<String, Object>(); 
variables.put("quote", obj); 

  // Start the process with custom class 
processServicesClient.startProcess(CONTAINER, processId, variables); } 

The above code should start the process . Please let me know how to fix this . Do I need to mention the QuoteDto Class anywhere else as well in order to map it correctly like in kmodule.xml or so ?