I’m trying to Serialize and Deserialize a Collection of data. But I’m still stuck on how to implement the handlers.
public interface Resource {
// Some logic goes here
}
public class Patient implements Resource {
//Patient Resource logic
}
public class Location implements Resource {
//Location Resource logic
}
@Test
public void dummyTest() {
List<Patient> patients = getPatients();
List<Location> locations = getLocations();
//Add the Resources to a Collection
HashMap<String, List<Resource>> resourceMap = new HashMap<String, List<Resource>>();
resourceMap.add("Patient", patients);
resourceMap.add("Location", locations);
//Serialize
String data = gson.toJson(resourceMap); // Works fine
//deserialize
HashMap deserializedObj = gson.fromJson(data, HashMap.class);
//Attempt getting a Patient object.
List<Resource> patientResources = deserializedObj.get("Patient");
for (Resource pat : patientResources) {
Patient patient = (Patient) pat; //Ooopppss, this throws an Exception."ClassCastException : gson.internal.LinkedTreeMap cannot be cast to Patient.class"
}
}
So I realized I had to implement my own customized Deserialization Handler. So I cameup with a ResourceDeserialization Handler.
public class ResourceDeserializer implements JsonDeserializer<Resource> {
@Override
public Resource deserialize(JsonElement json, Type type, JsonDeserializationContext context)
throws JsonParseException {
JsonObject jsonObject = json.getAsJsonObject();
if (jsonObject != null) {
return context.deserialize(jsonObject, getClassInstance(jsonObject.getAsString()));
}
return null;
}
private Class getClassInstance(String className) {
try {
return (Class)Class.forName(className);
} catch (ClassNotFoundException e) {
throw new JsonParseException(e.getMessage());
}
}
}
Now the challenge I face is here! Whats really next?
public HashMap<String, List<Resource>> deserialize(String json) {
Gson gson = new GsonBuilder().registerTypeAdapter(Resource.class, new ResourceDeserializer()).create();
// How can I do the actual Deserialization . This has blocked me a while.
/**
gson.fromJson(json, 'What goes here?');
*/
}
This has blocked me from completing the importing part of the module. Could someone help me here.
Its for exporting and importing Patient data. So I had planned to store the data in a Map<String, Resource> . Is there a better implementation?
So I’m planning to serialize the Map with data. The challenge is with deserialization. Actually casting a Resource to its type to be more specific.
Around. I tried to implement a deserialization handler but I need guidance here.
Btw, I made a mistake up there which am gonna edit. The Map looks like
Map<String, ArrayList<Resource>> store;
where we could add data like
List<Patient> patients = new ArrayList<Patient>();
List<Location> locations = new ArrayList<Location>();
// TODO :- Add some data to the lists.
HashMap<String, Resource> store = getStore();
//Add patient data to be serialized.
store.add("Patient", patients);
store.add("Location", locations);
//Serialize
String json = gson.toJson(store);
//Deserialize
HashMap<String, ArrayList<Resource>> deserializedData = gson.fromJson(json, HashMap<String, ArrayList<Resource>>);
//Try to retrieve Patient data.
List<Resource> patients = deserializedData.get("Patient");
for(Resource pat : patients) {
Patient patient = (Patient)pat;//Ooooppsss, throws ClassCastException : gson.internal.LinkedTreeMap cannot be cast to Patient.class
}
Now I realised I had to implement a deserialization Handler. Thats were I need yr help.
The above code my have typos. I have been just typing it from here just quickly
