Android (0.2.0) / Java (0.6.0)

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1. Overview

The Snowplow Java Tracker allows you to track Snowplow events from your Java-based desktop and server apps, servlets and games. It supports JDK6+.

The Snowplow Android Tracker allows you to track Snowplow events from your Android applications and games. It supports applications using the Android SDK 11 and above.

The tracker should be straightforward to use if you are comfortable with Java development; its API is modelled after Snowplow's Python Tracker so any prior experience with that tracker is helpful but not necessary. If you haven't already, have a look at the Java Tracker Setup or Android Tracker Setup guide before continuing.

1.1 Android specific

The Android Tracker is based off of the Java Tracker core library which was also used by the Java Tracker up to version 0.6.0. Hence, they both very similar in features and with a few differences in them. For sections of this documentation which only apply to Android, we will flag with a sub-section, Android Only.

2 Initialization

Assuming you have completed the Android Tracker Setup or Java Tracker Setup for your project, you are now ready to initialize the Android/Java Tracker.

2.1 Importing the module

Import the Java Tracker's classes into your Java code like so:

java

import com.snowplowanalytics.snowplow.tracker.*;

That's it - you are now ready to initialize a Tracker instance.

2.2 Understanding the module structure for Android

As we've mentioned in the setup guides, the Android Tracker is still based off a Java core library (which was part of the Java Tracker until version 0.6.0 inclusive). This means that for the Android Tracker you'll find a set the core libraries in com.snowplowanalytics.snowplow.tracker.core.*. If you're using the Android Tracker you would use the classes in com.snowplowanalytics.snowplow.tracker.android.*, since it contains class overrides specific to Android. If the class doesn't exist in that module (mostly enums), you can use the ones in the core package instead.

2.3 Creating a Tracker

To instantiate a tracker in your code (can be global or local to the process being tracked) simply instantiate the Tracker interface with one of the following:

java

Tracker(Emitter emitter, String namespace, String appId)
Tracker(Emitter emitter, Subject subject, String namespace, String appId)
Tracker(Emitter emitter, String namespace, String appId, boolean base64Encoded)
Tracker(Emitter emitter, Subject subject, String namespace, String appId, boolean base64Encoded)

For example:

java

Tracker t1 = new Tracker(emitter, user1Subject, "AF003", "cf", true);
Tracker t2 = new Tracker(emitter, "AF003", "cf");

Argument Name	Description	Required?
emitter	The Emitter object you create	Yes
subject	The subject that defines a user	No
namespace	The name of the tracker instance	Yes
appId	The application ID	Yes
base64Encoded	Whether to enable base 64 encoding	No (Default true)

2.3.1 emitter

The emitter to which the tracker will send events. See Emitters for more on emitter configuration.

2.3.2 subject

The user which the Tracker will track. This should be an instance of the Subject class. You don't need to set this during Tracker construction; you can use the Tracker.setSubject method afterwards. In fact, you don't need to create a subject at all. If you don't, though, your events won't contain user-specific data such as timezone and language.

2.3.3 namespace

If provided, the namespace argument will be attached to every event fired by the new tracker. This allows you to later identify which tracker fired which event if you have multiple trackers running.

2.3.4 appId

The appId argument lets you set the application ID to any string.

2.3.5 base64Encoded

By default, unstructured events and custom contexts are encoded into Base64 to ensure that no data is lost or corrupted. You can turn encoding on or off using the Boolean base64Encoded argument.

2.3.6 Change the tracker's platform with setPlatform

You can change the platform by calling:

java

tracker.setPlatform("cnsl");

For a full list of supported platforms, please see the Snowplow Tracker Protocol.

3. Adding extra data: the Subject class

You may have additional information about your application's environment, current user and so on, which you want to send to Snowplow with each event.

The Subject class has a set of set...() methods to attach extra data relating to the user to all tracked events:

• setUserId
• setScreenResolution
• setViewport
• setColorDepth
• setTimezone
• setLanguage

Here are some examples:

java

s1.setUserID("Kevin Gleason");
s1.setLanguage("en-gb");
s1.setScreenResolution(1920, 1080);

After that, you can add your Subject to your Tracker like so:

java

Tracker(emitter, s1, namespace, appId);
// OR
t1.setSubject(s1);

3.2 Set user ID with setUserId

You can set the user ID to any string:

java

s1.setUserId( "{{USER ID}}" )

Example:

java

s1.setUserId("alexd")

3.3 Set screen resolution with setScreenResolution

If your Java code has access to the device's screen resolution, then you can pass this in to Snowplow too:

java

t1.setScreenResolution( {{WIDTH}}, {{HEIGHT}} )

Both numbers should be positive integers; note the order is width followed by height. Example:

java

t1.setScreenResolution(1366, 768)

3.4 Set viewport dimensions with setViewport

If your Java code has access to the viewport dimensions, then you can pass this in to Snowplow too:

java

s.setViewport( {{WIDTH}}, {{HEIGHT}} )

Both numbers should be positive integers; note the order is width followed by height. Example:

java

s.setViewport(300, 200)

3.5 Set color depth with setColorDepth

If your Java code has access to the bit depth of the device's color palette for displaying images, then you can pass this in to Snowplow too:

java

s.setColorDepth( {{BITS PER PIXEL}} )

The number should be a positive integer, in bits per pixel. Example:

java

s.setColorDepth(32)

3.6 Set timezone with setTimezone

This method lets you pass a user's timezone in to Snowplow:

java

s.setTimezone( {{TIMEZONE}} )

The timezone should be a string:

java

s.setTimezone("Europe/London")

3.7 Set the language with setLanguage

This method lets you pass a user's language in to Snowplow:

java

s.setLanguage( {{LANGUAGE}} )

The language should be a string:

java

s.setLanguage('en')

4. Tracking specific events

Snowplow has been built to enable you to track a wide range of events that occur when users interact with your websites and apps. We are constantly growing the range of functions available in order to capture that data more richly.

Tracking methods supported by the Java Tracker at a glance:

Function	*Description
trackScreenView()	Track the user viewing a screen within the application
trackPageView()	Track and record views of web pages.
trackEcommerceTransaction()	Track an ecommerce transaction and its items
trackStructuredEvent()	Track a Snowplow custom structured event
trackUnstructuredEvent()	Track a Snowplow custom unstructured event

4.1 Common

All events are tracked with specific methods on the tracker instance, of the form trackXXX(), where XXX is the name of the event to track.

4.1.1 Custom contexts

In short, custom contexts let you add additional information about the circumstances surrounding an event in the form of a Map object. Each tracking method accepts an additional optional contexts parameter after all the parameters specific to that method:

java

t1.trackPageView(String pageUrl, String pageTitle, String referrer);
t1.trackPageView(String pageUrl, String pageTitle, String referrer, List<SchemaPayload> context);
t1.trackPageView(String pageUrl, String pageTitle, String referrer, double timestamp);
t1.trackPageView(String pageUrl, String pageTitle, String referrer, List<SchemaPayload> context, double timestamp);

The context argument should consist of a List of SchemaPayload representing an array of one or more contexts. The format of each individual context element is the same as for an unstructured event.

If a visitor arrives on a page advertising a movie, the context dictionary might look like this:

json

{
  "schema": "iglu:com.acme_company/movie_poster/jsonschema/2.1.1",
  "data": {
    "movie_name": "Solaris",
    "poster_country": "JP",
    "poster_year": "1978"
  }
}

Note that even if there is only one custom context attached to the event, it still needs to be placed in an array.

4.1.2 Optional timestamp & context argument

In all the trackers, we offer a way to set the timestamp if you want the event to show as tracked at a specific time. If you don't, we create a timestamp while the event is being tracked.

Here is an example:

java

t1.trackPageView("www.page.com", "Example Page", "www.referrer.com");
t1.trackPageView("www.page.com", "Example Page", "www.referrer.com", contextArray);
t1.trackPageView("www.page.com", "Example Page", "www.referrer.com", contextArray, 12348567890);
t1.trackPageView("www.page.com", "Example Page", "www.referrer.com", 12348567890);

4.1.3 Tracker method return values

To be confirmed. As of now, trackers do not return anything.

4.2 Track screen views with trackScreenView()

Use trackScreenView() to track a user viewing a screen (or equivalent) within your app. Arguments are:

Argument	Description	Required?	Validation
name	Human-readable name for this screen	No	String
id	Unique identifier for this screen	No	String
context	Custom context for the event	No	List
timestamp	Optional timestamp for the event	No	Long

Example:

java

t1.trackScreenView("HUD > Save Game", "screen23");
t1.trackScreenView("HUD > Save Game", contextList, 123456);

4.3 Track pageviews with trackPageView()

If you are using Java servlet technology or similar to serve webpages to a browser, you can use trackPageView() to track a user viewing a page within your app.

Arguments are:

Argument	Description	Required?	Validation
page_url	The URL of the page	Yes	String
page_title	The title of the page	Yes	String
referrer	The address which linked to the page	Yes	String
context	Custom context for the event	No	List
timestamp	Optional timestamp for the event	No	Long

Example:

java

t1.trackPageView("www.example.com", "example", "www.referrer.com", contextList);
t1.trackPageView("www.example.com", "example", "www.referrer.com");

4.4 Track ecommerce transactions with trackEcommerceTransaction()

Use trackEcommerceTransaction() to track an ecommerce transaction.

Arguments:

Argument	Description	Required?	Validation
order_id	ID of the eCommerce transaction	Yes	String
total_value	Total transaction value	Yes	Double
affiliation	Transaction affiliation	Yes	String
tax_value	Transaction tax value	Yes	Double
shipping	Delivery cost charged	Yes	Double
city	Delivery address city	Yes	String
state	Delivery address state	Yes	String
country	Delivery address country	Yes	String
currency	Transaction currency	Yes	String
items	Items in the transaction	Yes	List
context	Custom context for the event	No	Map
timestamp	Optional timestamp for the event	No	Long

The items argument is a List of individual TransactionItem elements representing the items in the e-commerce transaction. Note that trackEcommerceTransaction fires multiple events: one transaction event for the transaction as a whole, and one transaction item event for each element of the items List. Each transaction item event will have the same timestamp, order_id, and currency as the main transaction event.

4.4.1 Ecommerce TransactionItem with trackEcommerceTransaction()

To instantiate a TransactionItem in your code, simply use the following constructor signature:

java

trackEcommerceTransactionItem(String order_id, String sku, Double price, Integer quantity, String name, String category, String currency, Map context, long transaction_id)

These are the fields that can appear as elements in each TransactionItem element of the transaction item List:

Field	Description	Required?	Validation
order_id	Order ID	Yes	String
sku	Item SKU	No	String
price	Item price	No	double
quantity	Item quantity	No	int
name	Item name	No	String
category	Item category	No	String
currency	Item currency	No	String
context	Item context	No	List
timestamp	Optional timestamp for the event	No	Long

Example of tracking a transaction containing two items:

java

// Example to come, in the meantime here is the type signature:
t1.trackEcommerceTransaction(String order_id, Double total_value, String affiliation, Double tax_value,Double shipping, String city, String state, String country, String currency, List<TransactionItem> items, List<SchemaPayload> context);
t1.trackEcommerceTransaction("6a8078be", 300, "my_affiliate", 30, 10, "Boston", "Massachusetts", "USA", "USD", items, context);

4.5 Track structured events with trackStructuredEvent()

Use trackStructuredEvent() to track a custom event happening in your app which fits the Google Analytics-style structure of having up to five fields (with only the first two required):

Argument	Description	Required?	Validation
category	The grouping of structured events which this action belongs to	Yes	String
action	Defines the type of user interaction which this event involves	Yes	String
label	A string to provide additional dimensions to the event data	Yes	String
property	A string describing the object or the action performed on it	Yes	String
value	A value to provide numerical data about the event	Yes	Int
context	Custom context for the event	No	List
timestamp	Optional timestamp for the event	No	Long

Example:

java

t1.trackStructuredEvent("shop", "add-to-basket", "Add To Basket", "pcs", 2);
t1.trackStructuredEvent("shop", "add-to-basket", "Add To Basket", "pcs", 2, 123456.7);

4.6 Track unstructured events with trackUnstructuredEvent()

Custom unstructured events are a flexible tool that enable Snowplow users to define their own event types and send them into Snowplow.

When a user sends in a custom unstructured event, they do so as a JSON of name-value properties, that conforms to a JSON schema defined for the event earlier.

Use trackUnstructuredEvent() to track a custom event which consists of a name and an unstructured set of properties. This is useful when:

• You want to track event types which are proprietary/specific to your business (i.e. not already part of Snowplow), or
• You want to track events which have unpredictable or frequently changing properties

The arguments are as follows:

Argument	Description	Required?	Validation
eventData	The properties of the event	Yes	SchemaPayload
context	Custom context for the event	No	List
timestamp	Optional timestamp for the event	No	Long

Example:

java

t1.trackUnstructuredEvent(eventData, contextList);

For more on JSON schema, see the blog post.

5. Sending event: Emitter

Events are sent using an Emitter class. You can initialize an class with a collector endpoint URL with various options to choose how these events should be sent. Here are the Emitter interfaces that can be used:

java

Emitter(String URI)
Emitter(String URI, HttpMethod httpMethod)
Emitter(String URI, RequestCallback callback)
Emitter(String URI, HttpMethod httpMethod, RequestCallback callback)

For example:

java

Emitter e1 = new Emitter("d3rkrsqld9gmqf.cloudfront.net");
Emitter e2 = new Emitter("d3rkrsqld9gmqf.cloudfront.net", HttpMethod.POST);
Emitter e3 = new Emitter("d3rkrsqld9gmqf.cloudfront.net", new RequestCallback() {...});
Emitter e4 = new Emitter("d3rkrsqld9gmqf.cloudfront.net", HttpMethod.POST, new RequestCallback() {...});

Argument Name	Description	Required?
URI	The collector endpoint URI events will be sent to	Yes
httpMethod	The HTTP method events should be sent	No
callback	Lets you pass a callback class to handle succes/failure in sending events.	No

Android Only

For Android, the Emitter class is virtually the same in the way it is instantiated with the addition of an extra parameter to accept a Context. The Context is used for caching events in an SQLite database in order to avoid losing events to network related issues.

Here are what the Emitter interfaces for Android looks like:

java

Emitter(String URI, Context context)
Emitter(String URI, Context context, HttpMethod httpMethod)
Emitter(String URI, Context context, RequestCallback callback)
Emitter(String URI, HttpMethod httpMethod, RequestCallback callback, Context context)

For example, if you're creating an Emitter in an Activity class:

java

Emitter e1 = new Emitter("snowplow-collector.acme.com", this);
Emitter e2 = new Emitter("snowplow-collector.acme.com", this, HttpMethod.POST);
Emitter e3 = new Emitter("snowplow-collector.acme.com", this, new RequestCallback() {...});
Emitter e4 = new Emitter("snowplow-collector.acme.com", this, HttpMethod.POST, new RequestCallback() {...});

Argument Name	Description	Required?
URI	The collector endpoint URI events will be sent to	Yes
context	Used to use to open or create an SQLite database	Yes
httpMethod	The HTTP method events should be sent	No
callback	Lets you pass a callback class to handle succes/failure in sending events.	No

5.1 Using a buffer

A buffer is used to group events together in bulk before sending them. This is especially handy to reduce network usage. By default, the Emitter buffers up to 10 events before sending them. You can change this to send evenets instantly as soon as they are created like so:

java

Emitter e1 = new Emitter("d3rkrsqld9gmqf.cloudfront.net");
e1.setBufferOption(BufferOption.Instant);
// OR
e1.setBufferOption(BufferOption.Default);

Here are all the posibile options that you can use:

Option	Description
Instant	Events are sent as soon as they are created
Default	Sends events in a group when 10 events are created

5.2 Choosing the HTTP method

Snowplow supports receiving events via GET requests, but will soon have POST support. In a GET request, each event is sent in individual request. With POST requests, events are bundled together in one request.

You can set the HTTP method in the Emitter constructor:

java

Emitter e1 = new Emitter("d3rkrsqld9gmqf.cloudfront.net", HttpMethod.POST);

Here are all the posibile options that you can use:

Option	Description
GET	Sends events as GET requests
POST	Sends events as POST requests

5.3 Method of sending HTTP requests

An Emitter sends requests synchronously by default. If you want events to be sent asynchronously you can set this using setRequestMethod(RequestMethod):

java

Emitter e1 = new Emitter("d3rkrsqld9gmqf.cloudfront.net");
e1.setRequestMethod(RequestMethod.Asynchronous);

Here are all the possible options that you can use:

Option	Description
Synchronous	Sends events synchronously
Asynchronous	Sends events asynchronously

Android Only

For Android, we only send events asynchronously so we've deprecated the setRequestMethod method.

5.4 Emitter callback

If an event fails to send because of a network issue, you can choose to handle the failure case with a callback class to react accordingly. The callback class needs to implement the EmitterCallback interface in order to do so. Here is a sample bit of code to show how it could work:

java

Emitter emitter = new Emitter(testURL, HttpMethod.GET, new RequestCallback() {
  @Override
  public void onSuccess(int bufferLength) {
    System.out.println("Buffer length for POST/GET:" + bufferLength);
  }

  @Override
  public void onFailure(int successCount, List<Payload> failedEvent) {
    System.out.println("Failure, successCount: " + successCount + "\nfailedEvent:\n" + failedEvent.toString());
  }
});

In the example, we we can see an in-line example of handling the case. If events are all successfully sent, the onSuccess method returns the number of successful events sent. If there were any failures, the onFailure method returns the successful events sent (if any) and a list of events that failed to be sent (i.e. the HTTP state code did not return 200).

6. Payload

A Payload interface is used for implementing a TrackerPayload and SchemaPayload, but accordingly, can be used to implement your own Payload class if you choose.

6.1 Tracker Payload

A TrackerPayload is used internally within the Java Tracker to create the tracking event payloads that are passed to an Emitter to be sent accordingly.

6.2 Schema Payload

A SchemaPayload is used primarily as a wrapper around a TrackerPayload. After creating a TrackerPayload, you create a SchemaPayload and use setData with the Payload, followed by, setSchema to set the schema that the payload will be used against.

This is mainly used under the hood, in the Tracker class but is useful to know if you want to create your own Tracker class.

Here's a short example:

java

// This is our TrackerPayload that we created
TrackerPayload trackerPayload = new TrackerPayload();
trackerPayload.add("key", "value");

// We wrap that payload in a SchemaPayload before sending it.
SchemaPayload schemaPayload = new SchemaPayload();
schemaPayload.setData(trackerPayload);
schemaPayload.setSchema("iglu:com.snowplowanalytics.snowplow/example/jsonschema/1-0-0");

7. Logging

Logging in the Tracker is done using SLF4J. Majority of the logging set as DEBUG so will not overly populate your own logging.

Android Only

Logging in the Android Tracker uses Android's native logger set as DEBUG or ERROR with the [tag]([https://developer.android.com/reference/android/util/Log.html#d(java.lang.String](https://developer.android.com/reference/android/util/Log.html#d(java.lang.String), java.lang.String)) as the class name.

For example:

java

private final String TAG = Emitter.class.getName();
Log.e(TAG, "Cannot change RequestMethod: Asynchronous requests only available.");