Ormlite ForeignCollection with Gson

Question

Been struggling with this all day. I feel like I am one annotation away from the right solution.

I am getting an JSON from an API, and parsing it using Gson inside Volley request into a object. Then I want to store the object in DB, using ORMLite.

The problem is that my JSON has lists of other objects. So I have decided that ForeignCollection are required.

Here is simplified version of what I am getting as JSON:

{
    "b": [
        {"title"="abc","id="24sfs"},
        {"title"="def", "id="532df"}
    ],
    "c": [
        {"description"="abc","id="34325"},
        {"description"="def", "id="34321"}
    ],
    "id"="ejsa"
}

Lets call this whole object class A. The objects inside "b", are B, inside "c", class C.

B and C are the similar. This leads to the following class definitions:

class A {

    @DatabaseField(index = true, unique = true, id = true)
    private String id;
    @ForeignCollectionField(eager = true)
    public Collection<B> bCollection;
    public  ArrayList<B> b;
    @ForeignCollectionField(eager = true)
    public Collection<C> cCollection;
    public ArrayList<C> c;
}

class B  {
    @DatabaseField(foreign=true)
    public A a;
    @DatabaseField(id = true, index = true, unique = true)
    public String id;
    @DatabaseField
    public String title;
}

The reason we need the ArrayList b and c, is so that gson can parse it correctly. So once I have class A in memory, here is what I do to store it

private void storeA(A a) {
    if (a.b != null) {
        getHelper().getDao(B.class).callBatchTasks(new Callable<Void>() {
            @Override
            public Void call() throws Exception {
                for (B b : a.b) {
                    b.a = a;
                    try {
                        getHelper().getDao(B.class).createOrUpdate(b);
                    } catch (Exception e) {
                    }
                }
                return null;
            }
        });
    }

    /*
    Here we start running into problems. I need to move the data from the ArrayList to the Collection
    */
    a.bCollection = a.b; // but this seems to work, since bCollection is a Collection
    a.cCollection = a.c;
    getHelper().getDao(A.class).createOrUpdate(a);
}

So it seems to store correctly, no errors as far as I can tell. But when I try to retrieve as follows, I can't retrieve anything out of bCollection:

private void load() {
    try {
        List<A> as = getHelper().getDao(A.class).queryForEq("id", "ejsa");
        if (as != null && as.size() > 0) {
            A a = as.get(0);
            CloseableWrappedIterable<B> cwi = a.bCollection.getWrappedIterable();

            try {
                for (B b : cwi) {
                    Log.e(b.title);
                }
            } finally {
                cwi.close();
            }
        }
    } catch (Exception e) {
        e.printStackTrace();
    }
}

What am I doing wrong? Do I need to specify foreignColumnName for some of these things? I can't tell if the things are not being stored correctly or if I am just failing to retrieve them correctly?

Answer 1

I would try removing the following two lines:

a.bCollection = a.b;
a.cCollection = a.c;

A's ForeignCollection's should be auto-magically populated for you by ORMLite when you query for A, you do not need to set them yourself.