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I have a mobile app where a user fills out a form, say an Event, and when they save I want to submit the data as JSON to the server. CN1 has the feature to generate JSON easily using PropertyBusinessObject so my Event is defined as follows:

public class Event implements PropertyBusinessObject {

public final Property<Long, Event> eventId = new Property<>("eventId");
public final Property<EventLocation, Event> eventLocation = new Property<>("eventLocation", EventLocation.class);
public final Property<List<EventItinerary>, Event> eventItineraryList = new Property<>("eventItineraryList", XXX);
private final PropertyIndex idx...

}

Both EventLocation and EventItinerary implement PropertyBusinessObject and I've found that when I generate the JSON for Event, EventLocation generates fine but not EventItinerary. When I try and use EventItinerary.class in the "XXX" section above, I get the following error...

Exception: java.lang.ClassCastException - class java.util.ArrayList cannot be cast to class com.codename1.properties.PropertyBusinessObject

which occurs at line 484 of com.codename1.properties.PropertyIndex.toMapRepresentationImpl()

When I use List.class for "XXX" or nothing i.e. new Property<>("eventItineraryList"); then it posts to the server but the JSON contains the name of the class and its memory address i.e.

{
"eventId": 3425567,
"eventLocation" : {
...
},
"eventItineraryList": [
"com.myapp.event.EventItinerary@cdc543c",
"com.myapp.event.EventItinerary@39987ocb",
"com.myapp.event.EventItinerary@cd5t776c",
]
}

My question is what should I put in "XXX" to have the EventItinerary objects have the correct JSON representation?

Gabriel Kazama
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1 Answers1

0

You need to use a ListProperty so we can traverse into it and the ListProperty should refer to a different PropertyBusinessObject. So this should look roughly like this:

public final ListProperty<EventItinerary, Event> eventItineraryList = new ListProperty<>("eventItineraryList", EventItinerary.class);

Notice the EventItinerary.class which is important. The generic valuegets lost due to erasure. The argument lets us reconstruct the object with the right object types when loading from JSON.'

Also again, for this to work EventItinerary must be a PropertyBusinessObject too.

Shai Almog
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  • Thanks Shai. Did not see an example in the Developer guide and missed it in the API - was looking at things named PropertyXXX... – Gabriel Kazama Jun 29 '21 at 09:34
  • That is indeed an omission. I cover these in the courses/book and neglected the developer guide. This should be fixed. – Shai Almog Jun 30 '21 at 01:30