How to put and get an Class Instance from net.sf.json.JSONObject-CodePudding

I am using net.sf.json package for handling json. I have a Class named CustomerClass. I want to store an instance of this class in a JSON Object and retrieve the class instance later.

My Code :

    import net.sf.json.JSONObject;
    class Test {
        JSONObject test = new JSONObject;
        CustomerClass obj = new CustomerClass();
        test.put("objInstance", (Object) obj);
        CustomerClass retrievedInstance = (CustomerClass) test.get("objInstance"); // throws the error
    }
         
Error Thrown

java.lang.ClassCastException: class net.sf.json.JSONObject cannot be cast to class 
com.CustomerClass (net.sf.json.JSONObject and 
com.CustomerClass are in unnamed module of loader 
org.apache.catalina.loader.ParallelWebappClassLoader @18245eb0)

CodePudding user response：

According to the javadocs of JSONObject here,

The values can be any of these types: Boolean, JSONArray, JSONObject, Number, String, or the JSONNull object

So basically you cannot put any object it JSONObject and retrieve it later. If I try it will put {}.

public class CustomerClass {
 public CustomerClass(String string, String string2) {
 name = string;
 id=string2;
}
 String name;
 String id;
}
        
JSONObject test = new JSONObject();
CustomerClass obj = new CustomerClass("Hello", "Hi");
String testStr = "Hi";
test.put("objInstance",  (Object)obj);
test.put("str", testStr);
Object retrievedInstance =  test.get("objInstance"); // throws the error
String retrivedStr = (String)test.get("str");
System.out.println(retrivedStr);
System.out.println(retrievedInstance);
System.out.println(test);

Output:

Hi
{}
{"objInstance":{},"str":"Hi"}

So way out is you can use GSON library to map your Class CustomerClass to JSONObject and retrieve it later. Read this.