How can I use ORMLite with objects that contain ArrayLists of other objects?

Question

I have a Android java project with quite complex datatypes including ArrayLists of other complex datatypes. I’m trying to store my data in a database using ORMLite (4.42).

I have major problems converting between ArrayLists and ForeignCollection, has anyone manage to do this?

I don’t want a continuous sync with the database, instead I have a save method that saves the entire structure and a read method that restores the entire method. After an object is restored from the database, the object is sent via interfaces where the receiver expects a ArrayLists and not orm lite ForeignCollections.

My approach is the following. For each ArrayList I have a complementary ForeignCollection. Before storing an object to the database, the content of the ArrayList is copied to the ForeignCollection, and when read back, vice versa.

When I read out a data structure from the database, I want the ensure that the entire structure is restored since later on, the object will be sent to users that are not aware about orm lite package, thus I set eager = true.

My complex datatype looks like this:

@DatabaseTable(tableName = "accounts")
public class Account {

    @DatabaseField(generatedId = true)
    private int id;

    @ForeignCollectionField (eager = true, maxEagerLevel = 2)
    private ForeignCollection<Order> ordersFoC;
    private ArrayList<Order> ordersArL;

The Problem

Before storing the Account to the database, I tried to do the following. My hope was to copy the objects in the ArrayList to the ForeignCollection and the update the database with the Account object. The object myAccount has the same id as an object in the database so I expect an update of that object.

ordersFoC.addAll(orderArL);
myDao.createOrUpdate(myAccount);

No luck. The addAll method does directly write the orders to the database so I end up with duplicates of all orders since “addAll” adds and does not update any existing records.

So I tried to first remove all the orders from the database, but again with no luck:

ordersFoC.clear(); // Also tried: ordersFoC.removeAll(ordersFoC);
ordersFoC.addAll(orderArL);
myDao.createOrUpdate(myAccount);

The objects are not removed from the database. I read at groups.google.com (by Philip Fu) that this is a “known” problem with ormlite, that eager ForeignCollection does not play well with removeAll() or clear().

Is there a pattern that I have missed that allows me to work with objects that includes ArrayLists of complex types using the ormlite framework?

see http://stackoverflow.com/questions/18441595/how-to-store-the-arraylist-in-ormlite-database/31598771#31598771 for an easier solution — My House, Jul 23 '15 at 22:10

score 4 · Answer 1 · answered Mar 10 '13 at 19:38

I've got my code working with ArrayLists ok. I declared my fields like this:

@ForeignCollectionField(eager = true, maxEagerForeignCollectionLevel = 99)
private Collection<PersonalNameStructure> personalnamestructures = new ArrayList<>();

and the getter as

public List<PersonalNameStructure> getPersonalNameStructures() {
    return new ArrayList<>(personalnamestructures) ;
}

so it creates the ArrayList on the fly rather than trying to maintain it.

Obviously you may realise this already, but you also need to be careful around writing the objects as the eager setting affects reading foreign collections, it doesn't do anything for foreign fields or when writing a record.

You are creating a new instance of `ArrayList` from `personalnamestructures`. But I am just curious, have you checked the type of `personalnamestructures`? Could it be possible that it is of the type `ArrayList` already? — Yuchen, Jun 27 '16 at 20:26

How can I use ORMLite with objects that contain ArrayLists of other objects?

The Problem

1 Answers1