发布空值

Question

我正在研究REST项目。向端点发出POST请求时，它将接收空值。 这是该课程的摘录：

@POST
    @Consumes(MediaType.APPLICATION_JSON)
    @Produces(MediaType.APPLICATION_JSON)
    @Path("/STK")
    public Response STK(STKUtil stkutil) throws PSQLException, SQLException {
         Body body = stkutil.getBody();
         StkCallback stkcallback = new StkCallback();
         String merchantRequestID=stkcallback.getMerchantRequestID();
         String checkoutRequestID =  stkcallback.getCheckoutRequestID();
         int resultCode = stkcallback.getResultCode();
         String resultDesc = stkcallback.getResultDesc();   
        System.out.println("MerchantRequestID::"+merchantRequestID);     
        System.out.println("CheckoutRequestID::"+checkoutRequestID);  
        System.out.println("ResultCode::"+resultCode);
        System.out.println("ResultDesc::"+resultDesc);
       String stkcallBackResponse = "{\"ResultDesc\":\"Confirmation received succesfully\",\"ResultCode\":\"0\"}";
        System.out.println(stkcallBackResponse);
        return Response.status(201).entity(stkcallBackResponse).build();
}

这是具有getter和setter方法的课程：

public class STKUtil {
 Body BodyObject;


 // Getter Methods 

 public Body getBody() {
  return BodyObject;
 }

 // Setter Methods 

 public void setBody(Body BodyObject) {
  this.BodyObject = BodyObject;
 }
}
public class Body {
 StkCallback StkCallbackObject;


 // Getter Methods 

 public StkCallback getStkCallback() {
  return StkCallbackObject;
 }

 // Setter Methods 

 public void setStkCallback(StkCallback stkCallbackObject) {
  this.StkCallbackObject = stkCallbackObject;
 }
}
public class StkCallback {
 private String MerchantRequestID;
 private String CheckoutRequestID;
 private String ResultCode;
 private String ResultDesc;
 CallbackMetadata CallbackMetadataObject;


 // Getter Methods 

 public String getMerchantRequestID() {
  return MerchantRequestID;
 }

 public String getCheckoutRequestID() {
  return CheckoutRequestID;
 }

 public String getResultCode() {
  return ResultCode;
 }

 public String getResultDesc() {
  return ResultDesc;
 }

 public CallbackMetadata getCallbackMetadata() {
  return CallbackMetadataObject;
 }

 // Setter Methods 

 public void setMerchantRequestID(String MerchantRequestID) {
  this.MerchantRequestID = MerchantRequestID;
 }

 public void setCheckoutRequestID(String CheckoutRequestID) {
  this.CheckoutRequestID = CheckoutRequestID;
 }

 public void setResultCode(String ResultCode) {
  this.ResultCode = ResultCode;
 }

 public void setResultDesc(String ResultDesc) {
  this.ResultDesc = ResultDesc;
 }

 public void setCallbackMetadata(CallbackMetadata CallbackMetadataObject) {
  this.CallbackMetadataObject = CallbackMetadataObject;
 }
}
public class CallbackMetadata {
 ArrayList < Object > Item = new ArrayList < Object > ();

 // Getter Methods 

 // Setter Methods 

}

这是我要发布到端点的json请求：

{
 "Body": 
 {"stkCallback": 
  {
   "MerchantRequestID": "21605-295434-4",
   "CheckoutRequestID": "2017184930742",
   "ResultCode": "0",
   "ResultDesc": "The service request is processed successfully.",
   "CallbackMetadata": 
    { 
     "Item":  
     [
     {
       "Name": "Amount",
       "Value": 1
     },
     {
       "Name": "ReceiptNumber",
       "Value": "T6JSJJS"
     },
     {
       "Name": "Balance"
     },
     {
       "Name": "TransactionDate",
       "Value": 20171104184944
      },
     {
       "Name": "PhoneNumber",
       "Value": 777727894083
     }
     ]
    }
  }
 }
}

以下是成功发布后打印出来的回复：

Info:   MerchantRequestID::null
Info:   CheckoutRequestID::null
Info:   ResultCode::0
Info:   ResultDesc::null
Info:   UUID::f7cdc310-dcdb-445a-bc75-5e207b703415
Info:   {"ResultDesc":"Confirmation received succesfully","ResultCode":"0"}

我很困惑为什么要发布 null 值。