CODEWITHSUNDEEP
javaandroidgreendao
Emanuel
Emanuel

Reputation: 923

GreenDao getter for related entities returns empty list

I have an android app in which I use greenDAO to model my database. I have an easy scenario but I don't understand how I can make it work. I've followed the documentation but I must be missing something.

I have 3 entities: User, Picture and Address. A User has Pictures and Addresses. My getters for Picture and Address always return null.

    userEntity.getPicture(); -> returns null
    userEntity.getAddress(); -> returns null

Here is my GreenDAO setup

    Entity userEntity = schema.addEntity("User");
    userEntity.addIdProperty();
    userEntity.addStringProperty("firstName");
    userEntity.addStringProperty("lastName");

    Entity picture = schema.addEntity("Picture");
    picture.addIdProperty();
    picture.addByteArrayProperty("image");
    picture.addStringProperty("imageName");

    Entity address = schema.addEntity("Address");
    address.addIdProperty();
    address.addStringProperty("street");
    address.addIntProperty("houseNumber");
    address.addIntProperty("zipcode");
    address.addStringProperty("city");

    // a user can have multiple pictures but a picture is connected to one user
    Property pictureIdProperty = picture.addLongProperty("userId").getProperty();
    picture.addToOne(userEntity, pictureIdProperty).setName("user");
    userEntity.addToMany(picture, pictureIdProperty).setName("picture");

    // a user can have multiple addresses but an address is only connected to one user
    Property addressIdProperty = address.addLongProperty("userId").getProperty();
    address.addToOne(userEntity, addressIdProperty).setName("user");
    userEntity.addToMany(address, addressIdProperty).setName("address");

Here is my testclass to test the relations

    DevOpenHelper helper = new DaoMaster.DevOpenHelper(getApplication(), "relation_test_db", null);
    SQLiteDatabase db = helper.getWritableDatabase();
    DaoMaster daoMaster = new DaoMaster(db);
    this.daoSession = daoMaster.newSession();

    UserDao userDao = this.daoSession.getUserDao();
    PictureDao pictureDao = this.daoSession.getPictureDao();
    AddressDao addressDao = this.daoSession.getAddressDao();

    // clear all data
    userDao.deleteAll();
    pictureDao.deleteAll();
    addressDao.deleteAll();

    /**
     * create data
     */
    User bill = new User(null);
    bill.setFirstName("Bill");
    bill.setLastName("Murray");

    Picture billsPicture = new Picture(null);
    billsPicture.setImage("BillsExamplePictureByteArray".getBytes());
    billsPicture.setImageName("BillsPictureName");

    Address billsAddress = new Address(null);
    billsAddress.setStreet("BillsStreet");
    billsAddress.setHouseNumber(42);
    billsAddress.setZipcode(12345);
    billsAddress.setCity("Wilmette");

    billsPicture.setUser(bill);
    billsAddress.setUser(bill);

    userDao.insert(bill);
    pictureDao.insert(billsPicture);
    addressDao.insert(billsAddress);

    User user = userDao.queryBuilder().list().get(0);
    ArrayList<Picture> billsPictureList = (ArrayList<Picture>) user.getPicture();
    ArrayList<Address> billsAddressList = (ArrayList<Address>) user.getAddress();

    if (billsPictureList == null || billsPictureList.size() == 0) {
        // contact Markus
        Toast.makeText(this, "Contact Stackoverflow", Toast.LENGTH_SHORT).show();
        return;
    }

    if (billsAddressList == null || billsAddressList.size() == 0) {
        // contact Markus
        Toast.makeText(this, "Contact Stackoverflow", Toast.LENGTH_SHORT).show();
        return;
    }

Upvotes: 4

Views: 2640

Answers (1)

Sergii N.
Sergii N.

Reputation: 315

Emanuel,

I am facing some similar issues when trying to save objects with 1-to-1 relations.

After spending pretty enough time with greenDAO I have found, that all "relational" objects should have appropriate mapping IDs of their "parents" before being saved to DB.

So I may suggest, that if you take a look at setUser methods of your generated Picture and Address entities, you will see something like: 

public void setUser(User user) {
    synchronized (this) {
        this.user = user;
        userId = user == null ? null : user.getId();
        user__resolvedKey = userId;
    }
}

Crucial is userId = user == null ? null : user.getId();

There are race conditions, as your created User object will not get ID until it is actually saved to DB. And if it does not have ID, there is a chance, that setUser of its relational entities will not work normally.

In your case you may try to change save sequence to: 

//1. Save user to DB, this will give it ID  
userDao.insert(bill);  

//2. Set user entity with ID to its relational entities  
billsPicture.setUser(bill);  
billsAddress.setUser(bill);  

//3. Save relational entities  
pictureDao.insert(billsPicture);  
addressDao.insert(billsAddress);

Hope my answer will be helpful to you.

Upvotes: 3

Related Questions