Develop Reference

Realm: updateOrInsert without index

I have a RealmObject, which is used as a temporary data cache only (there will be many entries). I also wrote a static method add() so I can easily add a new entry, but it seems too complicated. Here is the whole class:
public class ExchangePairPriceCache extends RealmObject {
#Index
private String exchangeName;
#Index
private String baseCurrency;
#Index
private String quoteCurrency;
private float price;
private long lastPriceUpdate;
public ExchangePairPriceCache() {
exchangeName = "";
baseCurrency = "";
quoteCurrency = "";
price = 0;
lastPriceUpdate = 0;
}
public ExchangePairPriceCache(String exchangeName, String baseCurrency, String quoteCurrency) {
this.exchangeName = exchangeName;
this.baseCurrency = baseCurrency;
this.quoteCurrency = quoteCurrency;
price = 0;
lastPriceUpdate = 0;
}
public void setPrice(float price) {
// this needs to be called inside a Realm transaction if it's a managed object
this.price = price;
lastPriceUpdate = System.currentTimeMillis();
}
public float getPrice() {
return price;
}
/* static functions */
public static void add(String exchangeName, String baseCurrency, String quoteCurrency, float price) {
Realm realm = Realm.getDefaultInstance();
realm.executeTransaction(r -> {
ExchangePairPriceCache priceCache = r.where(ExchangePairPriceCache.class)
.equalTo("exchangeName", exchangeName)
.equalTo("baseCurrency", baseCurrency)
.equalTo("quoteCurrency", quoteCurrency).findFirst();
if(priceCache != null) {
priceCache.setPrice(price);
} else {
priceCache = new ExchangePairPriceCache(exchangeName, baseCurrency, quoteCurrency);
priceCache.setPrice(price);
ExchangePairPriceCache finalPriceCache = priceCache;
r.insert(finalPriceCache);
}
});
realm.close();
}
public static ExchangePairPriceCache get(String exchangeName, String baseCurrency, String quoteCurrency) {
Realm realm = Realm.getDefaultInstance();
ExchangePairPriceCache priceCache = realm.where(ExchangePairPriceCache.class)
.equalTo("exchangeName", exchangeName)
.equalTo("baseCurrency", baseCurrency)
.equalTo("quoteCurrency", quoteCurrency)
.greaterThan("lastPriceUpdate", System.currentTimeMillis() - TimeUnit.SECONDS.toMillis(10)).findFirst();
if(priceCache != null)
priceCache = realm.copyFromRealm(priceCache);
realm.close();
return priceCache;
}
public static void deleteAll() {
Realm realm = Realm.getDefaultInstance();
realm.executeTransaction(r -> r.delete(ExchangePairPriceCache.class));
realm.close();
}
}
Questions:
Is this a good design (having static functions for ease of use)? I like how I can insert new entries into cache like ExchangePairPriceCache.add("NASDAQ", "AAPL", "USD", 100.5); and delete all with ExchangePairPriceCache.deleteAll() when needed.
How can I simplify add() function? Right now I check if entry already exists and then update the price and if it doesn't, I create a new object and insert it into Realm. I am not able to use updateOrInsert because I don't have unique index for object.
Maybe I am just questioning myself too much and this is all good as it is. But I'd really appreciate some input from experts who use it daily.

You should use a "Repository design pattern" with a DAO object (Data Access Object), to do all your read/ write transactions in realm.
Model class should be a blind copy of objects just holding entities.
Since you do not have any unique identifiers, you can try below
Cache the Exchange pair in Shared preferences file (if they are added earlier or not)
For faster read/writes : Create a temporary unique identifier with a combination of key-value pair that you already have
eg : (exchangeName + baseCurrency + quoteCurrency) - Cast into proper formats to create some unique key with all these values.

Gson toJson not serializing specific values

I have this project I'm working on and I can't seem to get Gson to behave properly.
Here are the screenshots/files I will be referring to:
https://www.dropbox.com/sh/4qi2skij9knea7n/AACwkRV9x43lZeOoTZeCS3NPa?dl=0
I have my model, Trip:
public class Trip {
#Expose
#SerializedName("Id")
private String mId;
#Expose
#SerializedName("Name")
private String mName;
#Expose
#SerializedName("Date")
private String mShipmentDateString;
#Expose
#SerializedName("State")
private int mState;
#Expose
#SerializedName("Orders")
private List<Order> mOrders;
//Getters and setters
}
And that's it, nothing more.
I have created a separate project to try and understand this problem better, what I do in Main Activity is:
String jsonElement = JsonHelper.getString();
final TripResponse trips = new Gson().fromJson(jsonElement,
TripResponse.class);
TripRequest tripRequest = new TripRequest();
tripRequest.setTrips(trips.getTripList());
Gson gson = new GsonBuilder().serializeNulls().create();
String jsonWithBuilder = gson.toJson(tripRequest);
Gson gsonB2 = new GsonBuilder().excludeFieldsWithoutExposeAnnotation().serializeNulls().create();
String object = gsonB2.toJson(tripRequest);
This is what I get, as you can see even though the dateString exists and has a value it doesn't get serialized:
(look at image1 in the folder).
The funny thing is: if I swap the SerializedName between dateString and name, suddenly it serializes the date and not the name: (as you can see in image2 on dropbox).
Input and output (output starts at line 118) are in the file "INPUTANDOUTPUT" in the dropbox folder.
What am I missing?

I think it's because your are using two differentes #annotation for the same purpose :
#Expose // serialize the variable as mId
private String mId
#SerializedName("Id") // serialize the variable as Id
private String mId;
You can try to use just #SerializedName
Hope this helps
Sorry for my english.

Realm not saving (or possibly not returning) String values of related object

Realm not saving (or possibly not returning) String values of related object...
i have 3 models:
public class Customer extends RealmObject {
#Expose
#PrimaryKey
private Long id;
#Expose
private Long historicalId;
#Expose
private String versionUUID;
#Expose
private String nameCompany;
#Expose
private String email;
#Expose
private String phoneNumber;
#Expose
private String notes;
#Expose
private boolean active;
#Expose
private boolean currentVersion;
#Expose
private Date lastUpdated;
#Expose
private Date dateCreated;
public Customer() {
}
and
public class Project extends RealmObject {
#PrimaryKey
private Long id;
private Long historicalId;
private String versionUUID;
private String name;
private String description;
private String addressLineOne;
private String addressLineTwo;
private String addressCity;
private String addressState;
private String addressZip;
private String notes;
private Date lastUpdated;
private Date dateCreated;
private boolean active;
private boolean currentVersion;
private Customer customer;
private String customerVersion;
public Project() {
}
and lastly (added for the comment question)
public class Receipt extends RealmObject {
#PrimaryKey
private String id;
private String name;
private String vendor;
private Double amount;
private String description;
private Date dateCreated;
private Date lastUpdated;
private Date dateSynced;
private byte[] imageByteArray;
private Project project;
private String projectVersion;
private int imgWidht;
private int imgHeight;
public Receipt() {
}
i am saving the data via:
public static void syncAllDataToRealm(Context context){
Globals globals = Globals.getInstance();
Realm realm = Realm.getInstance(context);
realm.beginTransaction();
realm.copyToRealmOrUpdate(globals.getAllCustomers());
realm.copyToRealmOrUpdate(globals.getAllProjects());
realm.commitTransaction();
testRealCommit(context);
}
and i am verifying the data via
private static void testRealCommit(Context context){
Realm realm = Realm.getInstance(context);
RealmQuery<Customer> customerRealmQuery = realm.where(Customer.class);
RealmResults<Customer> customerRealmResults = customerRealmQuery.findAll();
logger.debug(LogUtility.generateMessage(TAG, "===== CUSTOMER ======= "));
for(Customer c: customerRealmResults){
logger.debug(LogUtility.generateMessage(TAG, c.getId() + " - " + c.getNameCompany()));
}
logger.debug(LogUtility.generateMessage(TAG, "===== CUSTOMER GLOBAL======= "));
for(Customer c: Globals.getInstance().getAllCustomers()){
logger.debug(LogUtility.generateMessage(TAG, c.getId() + " - " + c.getNameCompany()));
}
RealmQuery<Project> projectRealmQuery = realm.where(Project.class);
RealmResults<Project> projectRealmResults = projectRealmQuery.findAll();
logger.debug(LogUtility.generateMessage(TAG, "===== PROJECT ======="));
for(Project p: projectRealmResults){
logger.debug(LogUtility.generateMessage(TAG, p.getId() + " - " + p.getName()));
}
}
for some reason:
c.getNameCompany()
returns a null in the above code... if i dont add the project data to realm it works fine....
realm is bein set up in my Application file via:
RealmConfiguration config = new RealmConfiguration.Builder(context)
.name("receiptbucket.realm")
.schemaVersion(2)
.build();
Realm.setDefaultConfiguration(config);
any ideas???
found out something else... if i swap the commit order, adding all customers after adding all projects it works
realm.copyToRealmOrUpdate(globals.getAllProjects());
realm.copyToRealmOrUpdate(globals.getAllCustomers());
short term fix but i would like to know why i have to do it this way for the customer data to stick...
(New Issue)
now when i call copyOrUpdate for the Receipt it wipes all the customer data Projects Customer....

From your last description, I think the problem is the Project list returned by globals.getAllProjects() contains some Customer which has null value for nameCompany .
The reason is your Customer class has an id which is annotated with #PrimaryKey, when realm.copyToRealmOrUpdate(globals.getAllProjects()) called, Realm will create or update related objects recursively. (That is the whole point of update here).
If it finds a customer which has the same id and already saved in the Realm, it will just use all new values from Project.customer to update the one existed in the Realm. If the Procject.customer.nameCompany is null, you will have the problem you described above.
The solution would be make the globals.getAllProjects() return the latest value you want to update, since there is no way for Realm to understand whether the null values are something you want to ignore or update to.

i was able to overcome the last error by querying realm and reattaching the Customer that was getting nulled out to the Project which is part of the Receipt....
so then i started playing.... I was loading realm from Global data... I stopped that and loaded realm right when i got the data from my rest service...
upon doing that everything started just working correctly, lol...

Realm query with List

I'm using realm to store my data on Android. Awesome framework! Now the only problem I'm now having is:
I got a array list strings with id's of Countries in my database.
Now I retrieve my Drinks that contains a relationship to countries.
Is there a way that I could to do a query like this:
String [] ids;
realm.where(Drinks.class).equalsTo("country.id", ids);
Something like that?
Or do I really need to do a query to get me all drinks and then filter the list manually?
EDIT:
My classes:
public class Drinks extends RealmObject {
#PrimaryKey
private String id;
private String name;
private Country country;
}
public class Country extends RealmObject {
#PrimaryKey
private String id;
private String name;
}

What you want to do is possible with link queries in theory (searching for "country.id"), however link queries are slow. Also you'd need to concatenate a bunch of or() predicates together, and I would not risk that with a link query.
I would recommend using the following
public class Drinks extends RealmObject {
#PrimaryKey
private String id;
private String name;
private Country country;
#Index
private String countryId;
}
public class Country extends RealmObject {
#PrimaryKey
private String id;
private String name;
}
And when you set the Country in your class, you also set the countryId as country.getId().
Once you do that, you can construct such:
RealmQuery<Drinks> drinkQuery = realm.where(Drinks.class);
int i = 0;
for(String id : ids) {
if(i != 0) {
drinkQuery = drinkQuery.or();
}
drinkQuery = drinkQuery.equalTo("countryId", id);
i++;
}
return drinkQuery.findAll();

Since the Realm database has added RealmQuery.in() with the version 1.2.0
I suggest using something like this.
//Drinks
public class Drinks extends RealmObject {
#PrimaryKey
private String id;
private String name;
private String countryId;
//getter and setter methods
}
//Country
public class Country extends RealmObject {
#PrimaryKey
private String id;
private String name;
//getter and setter methods
}
The code to use inside activity/fragments to retrieve drink list
String[] countryIdArray = new String[] {"1","2","3"} //your string array
RealmQuery<Drinks> realmQuery = realm.where(Drinks.class)
.in("countryId",countryIdArray);
RealmResults<Drinks> drinkList = realmQuery.findAll();

In latest version of Realm 7+, you can use anyOf to match a field against a list of values.
anyOf("name", new String[]{"Jill", "William", "Trillian"})
in older versions, use in instead of anyOf and with kotlin use oneOf instead of in.
see this issue

To match a field against a list of values, use in. For example, to find the names “Jill,” “William,” or “Trillian”, you can use in("name", new String[]{"Jill", "William", "Trillian"}). The in predicate is applicable to strings, binary data, and numeric fields (including dates).
Doc.-> https://realm.io/docs/java/latest#queries

Manually updating a foreign key.

I am pretty much aware of the absence of foreign keys in Realm. But I encountered this issue. I receive data in a normalised way and I have to figure out how to properly persist the relations.
Example:
class User{
private int id;
private Email email;
}
class Email{
private int id;
private String address;
}
And I receive something like:
{user={id:1, emailId:1}}
How can I store this type of data in my existing realm object ?

You will have to parse the JSON yourself to setup the links. From your description it isn't clear if you User and Email is already in Realm, but if that is the case I would do something like this:
class User{
#PrimaryKey
private int id;
private Email email;
}
class Email{
#PrimaryKey
private int id;
private String address;
}
JSONObject json = new JSONObject("{id:1, emailId:1}");
realm.beginTransaction();
User user = realm.where(User.class).equalTo("id", json.getInt("id")).findFirst();
Email email = realm.where(Email.class).equalTo("id", json.getInt("emailId")).findFirst();
user.setEmail(email);
realm.commitTransaction();