运行时GSON对象类型转换

Question

I have a template object type ExternalActionReqBean having an object that any of the class can be set, by indicationg action fields

Lets say, if action="FROZEN" , ExternalActionReqBean->payload will ExternalActionFrozenReqBean class type, if action="UNFROZEN" ExternalActionUnFrozenReqBean class type will be used.

if payload is like following, what is the best practice to make this happen?

{"txnID":"txn","action":"FROZEN","resource":"PNSENDER","payload":{"msisdn_list”:[“xxxx”,”xxx”,”xxx”]}}

ExternalActionReqBean externalActionReqBean = GSON.fromJson(payload, ExternalActionReqBean.class);
             if("FROZEN".equals(externalActionReqBean.getAction())){
               // externalActionFrozenReqBean = GSON.fromJson(externalActionReqBean.getPayload(),ExternalActionFrozenReqBean.class);
             }

@Data
@AllArgsConstructor
public class ExternalActionReqBean {

   private String txnID;
   private String action;
   private String resource;
   private Object payload;

}



@Data
public class ExternalActionFrozenReqBean {

   private List<String> msisdn_list;

}

@Data
public class ExternalActionUnFrozenReqBean {

   private String result;

}

Answer 1

I have changed the ExternalActionReqBean class signature, its type gets converted to Generic, than use TypeToken as following.

@Data
@AllArgsConstructor
public class ExternalActionReqBean<T> {

   private String txnID;
   private String action;
   private String resource;
   private T payload;

}

Code:

 if ("FROZEN".equals(externalActionReqBean.getAction())) {
  Type complexType = new TypeToken<ExternalActionReqBean<ExternalActionFrozenReqBean>>() {}.getType();
  ExternalActionReqBean<ExternalActionFrozenReqBean> result = GSON.fromJson(payload, complexType);

}

Thanks for https://futurestud.io/tutorials/gson-advanced-generics , you can find more under "Deserialization of Generics"