[BUG] PropertyIndex().loadJSON(...) exceeds mem limit (Test Case)

[jsfan3]

After some days of very difficult debugging for the issue "Codename One App killed on iOS only (by jetsam reason per-process-limit), randomly", I found that the main cause of the memory problem is PropertyIndex().loadJSON(...), that in my actual app allocates about ~50.000 instances of a specific PBO, while the necessary number of instances is about ~500. Of course I discovered this bug when I started to count the instances. I have an huge number of PBOs, so this bug is multiplied for all my PBOs... that's why the app exceeds mem limit and crashes on iOS.

I prepared an easy test case with three PBOs.
On the first execution, these PBOs are created and saved to JSON. This is the log:

[EDT] 0:0:0,82 - This is the first execution of the app (no JSON saved)
[EDT] 0:0:0,168 - 1 PBO1 instances
[EDT] 0:0:0,168 - 20 PBO2 instances
[EDT] 0:0:0,168 - 80 PBO3 instances
[EDT] 0:0:0,207 - JSON saved, kill the app and open it again

On the second execution, this is the log:

[EDT] 0:0:0,78 - This is not the first execution of the app, we are going to retrieve data from JSON
[EDT] 0:0:0,190 - 1 PBO1 instances
[EDT] 0:0:0,190 - 400 PBO2 instances
[EDT] 0:0:0,190 - 3200 PBO3 instances

As you can see, in this test case we have 400 instances instead of 20 and 3200 instances instead of 80.

I attach a zip file with the test case made using Netbeans 10 and Java 8:
TestCasePBO_JSON.zip

This is the code:

MainClass

Form hi = new Form("Test Case PBOs to JSON", BoxLayout.y());
        hi.add(new Label("Test Case PBOs to JSON, see logs"));
        hi.show();

        if (!Storage.getInstance().exists("myJSON")) {
            Log.p("This is the first execution of the app (no JSON saved)");

            // I create "1" instance of PBO1
            PBO1 pbo1 = new PBO1();

            // I add "20" PBO2 items to the PBO1 map
            for (int i = 0; i < 20; i++) {
                pbo1.map.put(i + "", new PBO2());
            }

            // Note that each PBO2 instance has a list with "4" PBO3 instances,
            // so now we should have:
            // "1" PBO1 instance
            // "20" PBO2 instances
            // "80" PBO3 instances
            // Let's discover if it's true:
            Log.p(PBO1.getCounter() + " PBO1 instances");
            Log.p(PBO2.getCounter() + " PBO2 instances");
            Log.p(PBO3.getCounter() + " PBO3 instances");

            // Now we save PBO1 to JSON, PBO2 and PBO3 are implicitly included in the saving
            pbo1.getPropertyIndex().storeJSON("myJSON");
            Log.p("JSON saved, kill the app and open it again");

        } else {
            Log.p("This is not the first execution of the app, we are going to retrieve data from JSON");
            PBO1 pbo1 = new PBO1();
            pbo1.getPropertyIndex().loadJSON("myJSON");
            
            Log.p(PBO1.getCounter() + " PBO1 instances");
            Log.p(PBO2.getCounter() + " PBO2 instances");
            Log.p(PBO3.getCounter() + " PBO3 instances");
        }

PBO1.java

public class PBO1 implements PropertyBusinessObject {
    
    private static int counter = 0;
    
    public final Property<String, PBO1> name = new Property<>("name", "MyNameIsPBO1");
    public final MapProperty<String, PBO2, PBO1> map = new MapProperty<>("myMap", String.class, PBO2.class);

    private final PropertyIndex idx = new PropertyIndex(this, "PBO1",
        name, map);
    
    @Override
    public PropertyIndex getPropertyIndex() {
        return idx;
    }

    public PBO1() {
        counter++;
    }

    public static int getCounter() {
        return counter;
    }

}

PBO2.java

public class PBO2 implements PropertyBusinessObject {
    
    private static int counter = 0;
    
    public final Property<String, PBO2> name = new Property<>("name", "MyNameIsPBO2");
    public final ListProperty<PBO3, PBO2> list = new ListProperty<>("myList", PBO3.class, new PBO3(), new PBO3(), new PBO3(), new PBO3());

    private final PropertyIndex idx = new PropertyIndex(this, "PBO2",
        name, list);
    
    @Override
    public PropertyIndex getPropertyIndex() {
        return idx;
    }

    public PBO2() {
        counter++;
    }

    public static int getCounter() {
        return counter;
    }
    
}

PBO3.java

public class PBO3 implements PropertyBusinessObject {
    
    private static int counter = 0;
    
    public final Property<String, PBO3> name = new Property<>("name", "MyNameIsPBO3");

    private final PropertyIndex idx = new PropertyIndex(this, "PBO3",
        name);
    
    @Override
    public PropertyIndex getPropertyIndex() {
        return idx;
    }

    public PBO3() {
        counter++;
    }

    public static int getCounter() {
        return counter;
    }
    
}

[jsfan3]

As proof that storeJSON/loadJSON require too much memory, if I workaround the problem using Storage.writeObject/Storage.readObject the app doesn't crash and the number of PBOs instances is correct. However this workaround is not a proper solution and it's not useful when I need to share PBOs data with the server in JSON format. Moreover, storing to JSON helps to have human readable files.