Firebase ServerValue.TIMESTAMP in Java Data Model Objects

Question

I'm new to Firebase, and so far I really enjoyed it. I have a problem's; I am using FirebaseListAdapter, similar to the tutorial diagram here: https://github.com/firebase/AndroidChat

To use the FirebaseListAdapter, I need to use data model objects (for auto-binding to work well). The problem is that I also want to save the timestamp value with this model object, and I want to get the timestamp from the Firebase server.

I am not currently working, this is a DataModelObject class (similar to com.firebase.androidchat.Chat in a demo) with a constructor like:

DataModelObject(String data1, String data2, Map enQTimeStamp) 

which I then try to use as follows:

 DataModelObject dmo = new DataModelObject ("foo", "bar", ServerValue.TIMESTAMP); myFirebaseRef.push().setValue(dmo); 

This throws a JsonMappingException when I try to run this code. I found the code snippet here:

https://www.firebase.com/blog/2015-02-11-firebase-unique-identifiers.html

But it’s worth noting that in line 4 of the Android code example, this will cause a compile-time error (since it tries to put ServerValue.TIMESTAMP on the card, and TIMESTAMP is the card itself)

What is the right way to do this and maintain compatibility with FirebaseListAdapter?

Answer 1

This is similar to this question: When creating POJOs in Firebase, can you use ServerValue.TIMESTAMP?

When creating POJOs used to store / retrieve data other than an empty default constructor, I usually use a constructor like this:

 Param param1; Param param2; HashMap<String, Object> timestampCreated; //required empty constructor public DataObject(){} public DataObject(Param param1, Param param2) { this.param1 = param1; this.param2 = param2; HashMap<String, Object> timestampNow = new HashMap<>(); timestampNow.put("timestamp", ServerValue.TIMESTAMP); this.timestampCreated = timestampNow; } 

Be sure to enable the receiver for the HashMap <> used to store the timestamp:

 public HashMap<String, Object> getTimestampCreated(){ return timestampCreated; } 

Then use the @Exclude annotation to create a recipient that you can use in your code to get the timestamp value if you need it. @Exclude annotation will cause Firebase to ignore this getter and not look for the corresponding property

 @Exclude public long getTimestampCreatedLong(){ return (long)timestampCreated.get("timestamp"); } 

Answer 2

This is how i do it

 //member variable Object createdTimestamp; public YourConstructor(){ createdTimestamp = ServerValue.TIMESTAMP } @Exclude public long getCreatedTimestampLong(){ return (long)createdTimestamp; } 

Answer 3

Your db object should include the following:

 public class FirebaseDbObject { private final Object timestamp = ServerValue.TIMESTAMP; //........ //........ Object getTimestamp() { return timestamp; } @Exclude public long timestamp() { return (long) timestamp; } } 

This will add an extra field called a timestamp to your object.

Edit: The answer posted by MobileMon is not entirely correct, as it does not have a getter method. This is a complete and correct answer.

Answer 4

Kotlin provides an easy way to achieve this using data classes. You can create it like

 data class FirebaseRequestModel( var start_time: Any = ServerValue.TIMESTAMP, var stop_time: Long = 0, var total_time: Long = 0, ) 

and use it directly

 val firebaseModel = FirebaseRequestModel() firebaseRef.setValue(firebaseModel) 

This will get the default values ​​from the data class.

Or even you can initiate your own values ​​by

 val firebaseModel = FirebaseRequestModel(ServerValue.TIMESTAMP, 2134, 0) firebaseRef.setValue(firebaseModel) 

Answer 5

Similar to Urgurkan’s answer, but a little cleaner, so it’s easy for the caller to guess between getTimestamp and timestamp.

 public class FirebaseDbObject { private Object timestamp = ServerValue.TIMESTAMP; //........ //........ @PropertyName("timestamp") Object getRawTimestamp() { return timestamp; } @Exclude public long getTimestamp() { return (long) timestamp; } } 

Answer 6

You can do it:

 public class MyTimeStamp { private Object timestamp; public MyTimeStamp() { } public Object getTimestamp() { return timestamp; } public void setTimestamp(Object timestamp) { this.timestamp = timestamp; } } 

So:

 public static void start(Context context) { MyTimeStamp timeStamp = new MyTimeStamp(); timeStamp.setTimestamp(ServerValue.TIMESTAMP); Log.d(TAG, "start: ", timeStamp.getTimestamp().toString()); } 

Answer 7

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