JSON java.lang.Integer cannot be cast to java.lang.Long

[Christian Klugesherz]

Hello all,

I’m completely stuck with an issue.
There is now some days that I'm struggling about that issue :-(
I need really your help :-)

Same code, 2 different behaviors.
I am using json-simple
I have tested several approaches without success.
I know that JSON is returning a Long object.
But, even with that, why  in "Approach 1" the code is working, and not in "Approach 2" ?

With the following code

package pacp.test;

import org.json.simple.JSONObject;
import org.json.simple.parser.JSONParser;
import org.json.simple.parser.ParseException;

public class HelpJSON {

	// =====================================================================================
	// 											MAIN
	// =====================================================================================

	public static void main(String[] args) {

		Enthalpy enthalpy = new Enthalpy();

		// ======================
		// APPROACH 1
		// ======================
		System.out.println("\n APPROACH  1");
		System.out.println("---> Construct JSON data");
		JSONParser parser = new JSONParser(); 
		JSONObject jsonObjectR= null;
		String dataJSON = "{\"enthalpyBkgdImg\":{\"refCurveH1x\":140,\"enthalpyImageFile\":\"R22_A4.png\"},\"nameRefrigerant\":\"R22\",\"xHmin\":140.0}";
		try {
			jsonObjectR = (JSONObject) parser.parse(dataJSON);
		} catch (ParseException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		System.out.println(jsonObjectR);
		System.out.println("\n---> Set the Class Instance with JSON data");
		System.out.println(jsonObjectR);
		enthalpy.setJsonObject(jsonObjectR);

		// ======================
		// APPROACH  2
		// ======================
		System.out.println("\n APPROACH  2");
		System.out.println("---> Construct JSON data");
		JSONObject jsonObj = new JSONObject();
		jsonObj = enthalpy.getJsonObject();
		System.out.println(jsonObj);

		System.out.println("\n---> Set the Class Instance with JSON data");
		System.out.println(jsonObj);
		enthalpy.setJsonObject(jsonObj);

	}

	// =====================================================================================
	// 										CLASS ENTHALPYBKGIMG
	// =====================================================================================

	public static class EnthalpyBkgdImg {

		private String enthalpyImageFile;		
		private int refCurveH1x; 

		// -------------------------------------------------------
		// 						CONSTRUCTOR
		// -------------------------------------------------------

		public EnthalpyBkgdImg() {

			this.enthalpyImageFile = "R22 A4.png";
			this.refCurveH1x = 140; 
		}

		// -------------------------------------------------------
		// 							JSON
		// -------------------------------------------------------

		/**
		 * Construct the JSON data
		 * @return : JSONObject
		 */
		@SuppressWarnings("unchecked")
		public JSONObject getJsonObject() {
			JSONObject jsonObj = new JSONObject();  
			jsonObj.put("enthalpyImageFile", this.enthalpyImageFile);
			jsonObj.put("refCurveH1x", this.refCurveH1x);	
			return jsonObj ;
		}

		/**
		 * Set the JSON d<ata, to the Class instance
		 * @param jsonObj : JSON Object
		 */
		public void setJsonObject(JSONObject jsonObj) {
			this.enthalpyImageFile = (String) jsonObj.get("enthalpyImageFile");
			this.refCurveH1x = Integer.valueOf(((Long) jsonObj.get("refCurveH1x")).intValue()) ;
			//this.refCurveH1x = (int) jsonObj.get("refCurveH1x");
		}

	}

	// =====================================================================================
	// 										CLASS ENTHALPY
	// =====================================================================================

	public static class Enthalpy {

		private String nameRefrigerant;			
		private double xHmin;  					
		private EnthalpyBkgdImg enthalpyBkgdImg;

		// -------------------------------------------------------
		// 						CONSTRUCTOR
		// -------------------------------------------------------

		public Enthalpy() {
			nameRefrigerant = "R22";
			xHmin = 140;  				
			enthalpyBkgdImg = new EnthalpyBkgdImg();
		}

		// -------------------------------------------------------
		// 							JSON
		// -------------------------------------------------------

		/**
		 * Construct the JSON data
		 * @return : JSONObject
		 */
		@SuppressWarnings("unchecked")
		public JSONObject getJsonObject() {
			JSONObject jsonObj = new JSONObject();  
			jsonObj.put("nameRefrigerant", this.nameRefrigerant);
			jsonObj.put("xHmin", this.xHmin);	
			jsonObj.put("enthalpyBkgdImg", enthalpyBkgdImg.getJsonObject());	
			return jsonObj ;
		}

		/**
		 * Set the JSON data, to the Class instance
		 * @param jsonObj : JSON Object
		 */
		public void setJsonObject(JSONObject jsonObj) {
			this.nameRefrigerant = (String) jsonObj.get("nameRefrigerant");
			this.xHmin = (double) jsonObj.get("xHmin");
			JSONObject jsonObjEImg = (JSONObject) jsonObj.get("enthalpyBkgdImg");
			this.enthalpyBkgdImg.setJsonObject(jsonObjEImg); 
		}

	}

}

I get:

APPROACH  1
---> Construct JSON data
{"enthalpyBkgdImg":{"refCurveH1x":140,"enthalpyImageFile":"R22_A4.png"},"nameRefrigerant":"R22","xHmin":140.0}

---> Set the Class Instance with JSON data
{"enthalpyBkgdImg":{"refCurveH1x":140,"enthalpyImageFile":"R22_A4.png"},"nameRefrigerant":"R22","xHmin":140.0}

APPROACH  2
---> Construct JSON data
{"enthalpyBkgdImg":{"refCurveH1x":140,"enthalpyImageFile":"R22_A4.png"},"nameRefrigerant":"R22","xHmin":140.0}

---> Set the Class Instance with JSON data
{"enthalpyBkgdImg":{"refCurveH1x":140,"enthalpyImageFile":"R22_A4.png"},"nameRefrigerant":"R22","xHmin":140.0}
Exception in thread "main" java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.Long
at pacp.test.HelpJSON$EnthalpyBkgdImg.setJsonObject(HelpJSON.java:93)
at pacp.test.HelpJSON$Enthalpy.setJsonObject(HelpJSON.java:144)
at pacp.test.HelpJSON.main(HelpJSON.java:47)

ISSUE is located on

	this.refCurveH1x = Integer.valueOf(((Long) jsonObj.get("refCurveH1x")).intValue()) ;

When I replace that code with

			this.refCurveH1x = (int) jsonObj.get("refCurveH1x");

Vice versa "APPROACH 2" is working and not "APPROACH 1"

I become crazy...
How to fix that ?
Many thanks in advance

Regards

Christian

[Ron McLeod]

Since refCurveH1x is a numeric attribute, jsonObj.get("refCurveH1x") probably returns a type of Number.

If that is true, then you should be able to do: this.refCurveH1x = ((Number) jsonObj2.get("refCurveH1x")).intValue(); if you want to interpret the value as an int.

[Christian Klugesherz]

Thanks this is working... :-)

Nevertheless where is the logic
I read that:
The abstract class Number is the  superclass of platform classes representing numeric values that are convertible to the primitive types byte, double, float, int, long, and short.
as int refCurveH1x; so this.refCurveH1x = ((Number) jsonObj2.get("refCurveH1x")).intValue(); is OK
I'm using  
double xHmin; so normally I should also have the right to cast to "(Number)", for a same approach to JSON .get, but compiler doesn't accept
There is something that I didn't catch..

[Christian Klugesherz]

like:
this.xHmin = (Number) jsonObj.get("xHmin");

--> not accepted

[Christian Klugesherz]

Really sorry, My last answer has been sent to quickly ..

Answer was of course:

this.xHmin = ((Number) jsonObj.get("xHmin")).doubleValue(); 

Which is the logical code approach

Many many thanks

[Ron McLeod]

Christian Klugesherz wrote:like:
this.xHmin = (Number) jsonObj.get("xHmin");

--> not accepted

How about this?: this.xHmin = ((Number) jsonObj.get("xHmin")).doubleValue();

Edit: looks like you figured it out while I was typing

[Christian Klugesherz]

Yes !
Thanks Ron