I am using FCM to create a chat app, therefore both tokens and topics are being used. In my application I've created a POJO which extends RealmObject intended for storing the chat messages from different userIDs as well as the ones I've sent, both in private-chats and groups.
But what I can't understand is, how should I frame the Realm Query to retrieve the received messages and the messages I've sent to a UserID.
I'm thinking of trying:
RealmResults<ChatModel> results=mDatabase.where(TestChatModel.class)
.equalTo("sender",<Person with whom Im chatting's userID >)
.or()
.equalTo("receiver",<Person with whom Im chatting's userID >)
.and()
.equalTo("sender",<My userID >)
.or()
.equalTo("receiver",<My userID >
.sort("timestamp")
.findAll();
But that just seems very inefficient and messed up.
My POJO is:
public class TestChatModel {
private String chatMessage;
private String timestamp;
private String sender;
private String receiver;
private String topicName; // Set to NA is private-chat
private int isTopic; // Set to 0 for private-chat and Set to 1 for
// group
.
.
.
//Associated constructors and getters and setters
.
.
}
The community's help is much appreciated, thanks in advance !
Your query looks fine. All you can do is write down the query logic and then translate in into Realm query syntax. If your intention is to create a query with the criteria being that:
A specific person is either the sender or receiver, AND
The logged in user either the sender or receiver
Then that's probably the best way to do it. This assumes that you have ALL messages to and from everyone in the Realm; if you were to apply some other rule (e.g. that you only have messages including the logged in user in the Realm) then you could ditch clause 2, as this would be implied. An example of this would be if your API only provided messages for a logged in user (which seems like a reasonable scenario). That would improve efficiency and simplify the query.
In terms of other ways to improve efficiency, it's likely (although I have no direct evidence) that using a numerical ID for users rather than a string ID would allow for more efficient comparison and filtering in Realm. This would be preferable, but may depend on your API (again).
Finally, it's probably worth adding 'parentheses' to your query if it remains as above to ensure the operators are evaluated as you expect (i.e. the AND in the middle of the ORs). This can be accomplished with beginGroup and endGroup in the query (as described here).
This question already has answers here:
Create a GUID in Java
(7 answers)
Closed 5 years ago.
I am less acquainted with front end and am just a beginner in back end. I am creating a webpage using servlets that reads data of a person from the database and displays it on the page in a form of a list. Each row of the list, consists of a button to contact. When clicked on the button, a message is sent to the person whose data has been selected. My question is- how do we create a unique id from the button click to generate a message id in the message table of the database awaiting a response from the selected person?
All decent databases provide a way to generate unique IDs. A common way is through the usage of sequences, but it can even be simpler, PostgreSQL for example provides the SERIAL and BIGSERIAL types that automatically create a new id for each inserted row.
Long story made short: if you only need a different id for each row, use the equivalent of SERIAL provided by your database, and if you need greater control directly use a SEQUENCE (or its equivalent).
Use UUID Generator
Starting with Java 5, the UUID class provides a simple means for generating unique ids. The identifiers generated by UUID are actually universally unique identifiers.
Example
import java.util.UUID;
public class GenerateUUID {
public static final void main(String... aArgs){
//generate random UUIDs
UUID idOne = UUID.randomUUID();
UUID idTwo = UUID.randomUUID();
log("UUID One: " + idOne);
log("UUID Two: " + idTwo);
}
private static void log(Object aObject){
System.out.println( String.valueOf(aObject) );
}
}
Example run:
>java -cp . GenerateUUID
UUID One: 067e6162-3b6f-4ae2-a171-2470b63dff00
UUID Two: 54947df8-0e9e-4471-a2f9-9af509fb5889
Please refer : http://www.javapractices.com/topic/TopicAction.do?Id=56
I hope this will help.
I have been having a very unusual behavior when using Realm to insert and read/query data. Here is what is happening to be precise:
Initial Status
When I start to insert data to the database, everything works fine. I have the following code to handle autoIncrementingId since I have not found a version of Realm that offers this out of the box!
CashOrder cashOrder = new CashOrder();
realm.beginTransaction();
int lastCashOrderId;
RealmResults<CashOrder> cashOrders = realm.where(CashOrder.class).findAll();
cashOrders.sort("id", Sort.ASCENDING);
if (cashOrders.isEmpty()){
cashOrder.setId("0");
}else{
lastCashOrderId = Integer.parseInt(cashOrders.last().getId());
cashOrder.setId(String.valueOf(lastCashOrderId + 1));
}
//the rest of the code here
//then copyToRealm here;
realm.copyToRealm(cashOrder);
realm.commitTransaction();
The problem
Insertion of data into the database works just fine but the moment the id value reaches 10 - implying 11 items in the table since my id starts at (0), I get a Realm Primary Key Exception which basically complains that I am trying to add an already existing object.
I am explicitly calling realm.copyToRealm(obj) instead of realm.copyToRealmOrUpdate(obj) because that is what I want to do. Updates only are allowed when doing an Edit.
I am stuck here and I can't seem to figure out what is causing this issue!
More information
I am using:
compile 'io.realm:realm-android:0.87.4'
I will truly appreciate your help on this! Thanks in advance!
It's because your ID is a STRING and therefore it's ordered as 1, 10, 2, 3, ... 9.
This means when you evaluate the "next ID" when you had already inserted "10",
lastCashOrderId = Integer.parseInt(cashOrders.last().getId());
lastCashOrderId will be 9, and you'll be inserting 10 again.
Solution: use long id for longs, or re-think your auto-increment IDs (f.ex. use UUID.randomString() or something)
P.S. you should use findAllSorted() instead of findAll().sort() for consistent behavior when you update to the newer Realm versions.
EDIT: please use long newId = realm.where(CashOrder.class).max("age").longValue() + 1; to evaluate the new ID, and do this while you're in a transaction.
Messy, complicated question, but here goes. I'm working on an integration project with Google Checkout, and there is a Google Checkout GWT service that returns the currency conversion rates used by the Checkout web interface to convert USD into local currencies. This endpoint is hosted at https://market.android.com/publish/gwt/, and staring at Firebug I see this going to the server:
7|0|6|https://market.android.com/publish/gwt/|FCCA4108CB89BFC2FEC78BA7363D4AF6|com.google.wireless.android.vending.developer.
shared.MerchantService|getCurrencyExchangeRates|com.google.common.money.CurrencyCode/112449834|java.util.ArrayList/4159755760
|1|2|3|4|2|5|6|5|235|6|13|5|18|5|81|5|53|5|72|5|102|5|121|5|177|5|175|5|205|5|204|5|55|5|86|-1|
and this being returned
//OK[235,3,'D0JA',2,86,3,'CXXg',2,55,3,'DW2A',2,204,3,'X9NA',2,205,3,'EuvA',2,175,3,'VIig',2,177,3,'E2Dw',2,121,3,'E4ziA',2,1
02,3,'do$Q',2,72,3,'T82w',2,53,3,'Ds0Q',2,81,3,'Cq5g',2,18,3,'Dlfg',2,13,1,["com.google.common.collect.RegularImmutableList/4
40499227","com.google.common.money.SimpleMoney/627983206","com.google.common.money.CurrencyCode/112449834"],0,7]
Forgive the odd formatting: can't quite get the code block to format right.
Wandering the web for hours on end I was able to determine that the RegularImmutableList class is in the Guava libraries (at http://code.google.com/p/guava-libraries/). What I'm looking for is:
I can't find the com.google.common.money.SimpleMoney or com.google.common.money.CurrencyCode classes anywhere: anyone seen them?
The GWT wire format appears to be an odd JSON string. I see various references to Google Groups messages talking about descriptions of the wire format, but can't find the underlying messages or any coherent reference that would let me reverse this: anyone have a handle on a handy reference? If I can at least understand WHAT the encoding is I might be able to get away without the class files from question 1 above.
I started wandering through the Android Market api library at http://code.google.com/p/android-market-api/, figuring they have to have done SOME of the Android Market communication integration, and they appear to have done so using protobufs. Is there any decent reference for the GWT/protobufs communication bits?
The underlying reason for this craziness is that I need to be able to take regular exchange rate values from Google Checkout so when I'm importing sales transactions in foreign currencies I can do the conversion at the prevailing rate at the time of the transaction. The current Checkout reporting formats do NOT provide this, so most folks end up using alternative sources of exchange rates that don't match what Google uses. It is clearly a shortcoming on the part of Google Checkout's integration interface, but if we got started on shortcomings of Google Checkout's interface we'd be here all week. My intention is to poll the Checkout interface for newly fulfilled orders and then request the appropriate exchange rate table so I can figure out in near real-time what the incoming payments are. I've got the polling bit down pat but can't quite get past the exchange rate bit.
While trying to create a script to bulk upload in-app products for my application (CSV upload constantly failed with obscure error messages), I have managed to understand the GWT AJAX protocol.
It's actually pretty simple, except it requires you to know structure of all used classes. Or guess it, as is the case with internal classes used by Google. :)
I'll use examples from the question to explain the protocol in detail.
Request format
7|0|6|https://market.android.com/publish/gwt/|FCCA4108CB89BFC2FEC78BA7363D4AF6|com.google.wireless.android.vending.developer.shared.MerchantService|getCurrencyExchangeRates|com.google.common.money.CurrencyCode/112449834|java.util.ArrayList/4159755760|1|2|3|4|2|5|6|5|235|6|13|5|18|5|81|5|53|5|72|5|102|5|121|5|177|5|175|5|205|5|204|5|55|5|86|-1|
The request is pipe-delimited list of tokens with the following meaning:
7 - protocol version
0 - flags. 1 is FLAG_ELIDE_TYPE_NAMES, 2 is FLAG_RPC_TOKEN_INCLUDED
6 - string token count
6 string tokens:
https://market.android.com/publish/gwt/
FCCA4108CB89BFC2FEC78BA7363D4AF6
com.google.wireless.android.vending.developer.shared.MerchantService
getCurrencyExchangeRates
com.google.common.money.CurrencyCode/112449834
java.util.ArrayList/4159755760
The actual encoded request, which references strings from the list above using 1-based indices:
1 - https://market.android.com/publish/gwt/ - base URL
2 - FCCA4108CB89BFC2FEC78BA7363D4AF6 - some hash, which is references as serializationPolicyStrongName in GWT sources.
3 - com.google.wireless.android.vending.developer.shared.MerchantService - service name
4 - getCurrencyExchangeRates - method name
2 - parameter count. Parameter types follow:
5 - com.google.common.money.CurrencyCode/112449834
6 - java.util.ArrayList/4159755760
Serialized parameters. Each object is represented either by its classname and list of serialized fields or by negative integer back-reference to previously encountered object. In our case we have two objects:
5 - com.google.common.money.CurrencyCode/112449834, which only has one integer field: 235
6 - java.util.ArrayList/4159755760, which has one integer length field 13, followed by 13 serialized list items. Note that 12 of them are CurrencyCode objects serialized just as the above one, and the last one is a backreference (-1) to the very first object we encountered while (de-)serializing this request, i.e. CurrencyCode(235)
Response format
//OK[235,3,'D0JA',2,86,3,'CXXg',2,55,3,'DW2A',2,204,3,'X9NA',2,205,3,'EuvA',2,175,3,'VIig',2,177,3,'E2Dw',2,121,3,'E4ziA',2,102,3,'do$Q',2,72,3,'T82w',2,53,3,'Ds0Q',2,81,3,'Cq5g',2,18,3,'Dlfg',2,13,1,["com.google.common.collect.RegularImmutableList/440499227","com.google.common.money.SimpleMoney/627983206","com.google.common.money.CurrencyCode/112449834"],0,7]
The response is very similar in format to the request except it's JS-formatted array (though not JSON, as it uses invalid single quotes), and it's in reverse order.
The field meaning is as follows:
7 - protocol version
0 - flags, same as for request
Array of string tokens:
com.google.common.collect.RegularImmutableList/440499227
com.google.common.money.SimpleMoney/627983206
com.google.common.money.CurrencyCode/112449834
And then goes one serialized object of type 1 - com.google.common.collect.RegularImmutableList/440499227 with one integer length field 13, followed by 13 serialized objects of class 2 - com.google.common.money.SimpleMoney/627983206. Each SimpleMoney object has two fields, for example:
'Dlfg' - long integer field encoded as base64 number. This particular one is 940000
3, 18 - CurrencyCode object with integer field 18
What you are looking at is GWT-RPC serialization format. Unfortunatelly it is not publicly documented. Fortunatelly GWT is open-source so you could look at the source to see how it is produced.
Note: This format might change between GWT versions (I known it did in 2.2). This is most likelly also a reason why Google does not document it - if they did they'd need to keep it backward compatible.
Class names that you see are Java classes that Google Checkout uses internally. When GWT is compiled to JS the names get mangled so you don't see them any more.
As noted this is GWT-RPC.
What you are trying to do is reverse-engineer Google internal APIs. I wouldn't do that because, a. It might change without notice, breaking your app and, b. I'm sure Goog wouldn't like it and it probably violates the service agreement (have you read it?).
I have some code made in VB that may be useful for you to realize how to parse GWT Serialized strings. "Datos" contains the string you received.
aAux = Split(Datos, ",[")
aAux(1) = Replace(aAux(1), "],0,7]", "")
aAux(0) = Replace(aAux(0), "//OK[", "")
aAux(0) = Replace(aAux(0), "'", "")
aDescripcion = Split(aAux(1), """,""")
aValor = Split(aAux(0), ",")
InvertirArray aValor
For X = 0 To UBound(aValor)
If Not IsNumeric(aValor(X)) Then
Exit For
End If
If adescripcion(Int(aValor(X))-1) = "gov.senasa.embalajemadera.shared.domain.Pais/3238585366" Then
For Y = X + 1 To UBound(aValor)
If Int(aValor(Y)) = "" Then '- Do what you want
end if
If adescripcion(Int(aValor(Y))) = "java.lang.Integer/3438268394" Then
'- Do what you want
Next Y
End If
Next X
Of course you have to adapt it to your needs and you will have to play a little bit with the arrays...
InvertirArray:
Public Sub InvertirArray(ByRef Arr() As String)
'- el array va tiene que empezar en 0
Dim X As Long
Dim Hasta As Long
Dim Tmp As String
If UBound(Arr) Mod 2 = 0 Then
'- Es impar
Hasta = UBound(Arr) + 1
Else
Hasta = UBound(Arr)
End If
For X = LBound(Arr) To UBound(Arr) \ 2
Tmp = Arr(X)
Arr(X) = Arr(UBound(Arr) - X)
Arr(UBound(Arr) - X) = Tmp
Next X
end sub
And of course you need to decode and encode Long Numbers and dates. So:
Public Function EncodeDateGwt(Numero As Double, Optional isDate As Boolean = False) As String
Dim s As String
Dim a As Double
Dim i As Integer
Dim u As Integer
Dim Base As String
Numero = IIf(isDate, Numero * 1000, Numero)
Base = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_$"
Do While Val(Numero) <> 0
a = Numero
i = 0
Do While a >= 64
i = i + 1
a = a / 64
Loop
If i <> u - 1 And u <> 0 Then EncodeDateGwt = EncodeDateGwt & String(u - i - 1, Left(Base, 1))
a = Int(a)
EncodeDateGwt = EncodeDateGwt + Mid(Base, a + 1, 1)
Numero = Numero - a * (64 ^ i)
u = i
Loop
EncodeDateGwt = EncodeDateGwt & String(i, Left(Base, 1))
End Function
Public Function DecodeDateGwt(Texto As String, Optional isDate As Boolean = False) As Long
Dim Base As String
Dim a As Integer
Base = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_$"
For a = 1 To Len(Texto)
DecodeDateGwt = DecodeDateGwt + (InStr(Base, Mid(Texto, a, 1)) - 1) * (Len(Base) ^ ((Len(Texto) - (a))))
Next
DecodeDateGwt = IIf(isDate, DecodeDateGwt / 1000, DecodeDateGwt)
'devuelve timestamp
End Function
If what you need to encode/decode is a date, then you need to do this before:
Call encodegwtdate(date2unix("20/02/2016"),true)
Public Function Date2Unix(ByVal vDate As Date) As Long
Date2Unix = DateDiff("s", Unix1970, vDate)
End Function
Public Function Unix2Date(vUnixDate As Long) As Date
Unix2Date = DateAdd("s", vUnixDate, Unix1970)
End Function
Hope you solve it. By the way, does anyone knows what negative numbers means?????