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airbnb
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Description

A simple, annotation-based library for making deep link handling better on Android

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DeepLinkDispatch

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DeepLinkDispatch provides a declarative, annotation-based API to define application deep links.

You can register an

Activity
to handle specific deep links by annotating it with
@DeepLink
and a URI. DeepLinkDispatch will parse the URI and dispatch the deep link to the appropriate
Activity
, along with any parameters specified in the URI.

Example

Here's an example where we register

SampleActivity
to pull out an ID from a deep link like
example://example.com/deepLink/123
. We annotated with
@DeepLink
and specify there will be a parameter that we'll identify with
id
.
@DeepLink("example://example.com/deepLink/{id}")
public class SampleActivity extends Activity {
  @Override protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    Intent intent = getIntent();
    if (intent.getBooleanExtra(DeepLink.IS_DEEP_LINK, false)) {
      Bundle parameters = intent.getExtras();
      String idString = parameters.getString("id");
      // Do something with idString
    }
  }
}

Multiple Deep Links

Sometimes you'll have an Activity that handles several kinds of deep links:

@DeepLink({"foo://example.com/deepLink/{id}", "foo://example.com/anotherDeepLink"})
public class MainActivity extends Activity {
  @Override protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    Intent intent = getIntent();
    if (intent.getBooleanExtra(DeepLink.IS_DEEP_LINK, false)) {
      Bundle parameters = intent.getExtras();
      String idString = parameters.getString("id");
      // Do something with idString
    }
  }
}

Method Annotations

You can also annotate any

public static
method with
@DeepLink
. DeepLinkDispatch will call that method to create the
Intent
and will use it when starting your
Activity
via that registered deep link:
@DeepLink("foo://example.com/methodDeepLink/{param1}")
public static Intent intentForDeepLinkMethod(Context context) {
  return new Intent(context, MainActivity.class)
      .setAction(ACTION_DEEP_LINK_METHOD);
}

If you need access to the

Intent
extras, just add a
Bundle
parameter to your method, for example:
@DeepLink("foo://example.com/methodDeepLink/{param1}")
public static Intent intentForDeepLinkMethod(Context context, Bundle extras) {
  Uri.Builder uri = Uri.parse(extras.getString(DeepLink.URI)).buildUpon();
  return new Intent(context, MainActivity.class)
      .setData(uri.appendQueryParameter("bar", "baz").build())
      .setAction(ACTION_DEEP_LINK_METHOD);
}

If you're using Kotlin, make sure you also annotate your method with

@JvmStatic
.
companion objects
will not work, so you can use an
object declaration
instead:
object DeeplinkIntents {
  @JvmStatic 
  @DeepLink("https://example.com")
  fun defaultIntent(context: Context, extras: Bundle): Intent {
    return Intent(context, MyActivity::class.java)
  }
}

If you need to customize your

Activity
backstack, you can return a
TaskStackBuilder
instead of an
Intent
. DeepLinkDispatch will call that method to create the
Intent
from the
TaskStackBuilder
last
Intent
and use it when starting your
Activity
via that registered deep link:
@DeepLink("http://example.com/deepLink/{id}/{name}")
public static TaskStackBuilder intentForTaskStackBuilderMethods(Context context) {
  Intent detailsIntent =  new Intent(context, SecondActivity.class).setAction(ACTION_DEEP_LINK_COMPLEX);
  Intent parentIntent =  new Intent(context, MainActivity.class).setAction(ACTION_DEEP_LINK_COMPLEX);
  TaskStackBuilder  taskStackBuilder = TaskStackBuilder.create(context);
  taskStackBuilder.addNextIntent(parentIntent);
  taskStackBuilder.addNextIntent(detailsIntent);
  return taskStackBuilder;
}

Query Parameters

Query parameters are parsed and passed along automatically, and are retrievable like any other parameter. For example, we could retrieve the query parameter passed along in the URI

foo://example.com/deepLink?qp=123
:
@DeepLink("foo://example.com/deepLink")
public class MainActivity extends Activity {
  @Override protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    Intent intent = getIntent();
    if (intent.getBooleanExtra(DeepLink.IS_DEEP_LINK, false)) {
      Bundle parameters = intent.getExtras();
      if (parameters != null && parameters.getString("qp") != null) {
        String queryParameter = parameters.getString("qp");
        // Do something with the query parameter...
      }
    }
  }
}

Configurable path segment placeholders

Configurable path segment placeholders allow your to change configured elements of the URL path at runtime without changing the source of the library where the deeplink is defined. That way a library can be used in multiple apps that are still uniquely addressable via deeplinks. They are defined by encapsulating an id like this

 and are only allowed as a path segment (between two slashes. 
/
:
@DeepLink("foo://cereal.com//nutritional_info")
public static Intent intentForNutritionalDeepLinkMethod(Context context) {
  return new Intent(context, MainActivity.class)
      .setAction(ACTION_DEEP_LINK_METHOD);
}

If you do this you do have to provide a mapping (at runtime) for which values are allowed for creating a match. This is done when you new the

DeeplinkDelegate
class like:
@DeepLinkHandler({ AppDeepLinkModule.class, LibraryDeepLinkModule.class })
public class DeepLinkActivity extends Activity {
  @Override protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    // Configure a map for configurable placeholders if you are using any. If you do a mapping
    // has to be provided for that are used
    Map configurablePlaceholdersMap = new HashMap();
    configurablePlaceholdersMap.put("type_of_cereal", "obamaos");
    // DeepLinkDelegate, LibraryDeepLinkModuleRegistry and AppDeepLinkModuleRegistry
    // are generated at compile-time.
    DeepLinkDelegate deepLinkDelegate = 
        new DeepLinkDelegate(new AppDeepLinkModuleRegistry(), new LibraryDeepLinkModuleRegistry(), configurablePlaceholdersMap);
    // Delegate the deep link handling to DeepLinkDispatch. 
    // It will start the correct Activity based on the incoming Intent URI
    deepLinkDelegate.dispatchFrom(this);
    // Finish this Activity since the correct one has been just started
    finish();
  }
}

This app will now match the Url

foo://cereal.com/obamaos/nutritional_info
to the
intentForNutritionalDeepLinkMethod
method for that app. If you build another app and set
type_of_cereal
to
captnmaccains
that apps version of the
intentForNutritionalDeepLinkMethod
would be called when when opening
foo://cereal.com/captnmaccains/nutritional_info

If you are using configurable path segment placeholders, a mapping has to be provided for every placeholder used. If you are missing one the app will crash at runtime.

Empty configurable path segment placeholders mapping

A mapping can be to an empty string, in that case the element is just ignored. In the above example if

configurablePlaceholdersMap.put("type_of_cereal", "");
is defined
foo://cereal.com/nutritional_info
would map to calling the
intentForNutritionalDeepLinkMethod
method. An empty configurable path segment placeholder is not allowed as the last path element in an URL!

Callbacks

You can optionally register a

BroadcastReceiver
to be called on any incoming deep link into your app. DeepLinkDispatch will use
LocalBroadcastManager
to broadcast an
Intent
with any success or failure when deep linking. The intent will be populated with these extras:
  • DeepLinkHandler.EXTRA_URI
    : The URI of the deep link.
  • DeepLinkHandler.EXTRA_SUCCESSFUL
    : Whether the deep link was fired successfully.
  • DeepLinkHandler.EXTRA_ERROR_MESSAGE
    : If there was an error, the appropriate error message.

You can register a receiver to receive this intent. An example of such a use is below:

public class DeepLinkReceiver extends BroadcastReceiver {
  private static final String TAG = "DeepLinkReceiver";

@Override public void onReceive(Context context, Intent intent) { String deepLinkUri = intent.getStringExtra(DeepLinkHandler.EXTRA_URI); if (intent.getBooleanExtra(DeepLinkHandler.EXTRA_SUCCESSFUL, false)) { Log.i(TAG, "Success deep linking: " + deepLinkUri); } else { String errorMessage = intent.getStringExtra(DeepLinkHandler.EXTRA_ERROR_MESSAGE); Log.e(TAG, "Error deep linking: " + deepLinkUri + " with error message +" + errorMessage); } } }

public class YourApplication extends Application { @Override public void onCreate() { super.onCreate(); IntentFilter intentFilter = new IntentFilter(DeepLinkHandler.ACTION); LocalBroadcastManager.getInstance(this).registerReceiver(new DeepLinkReceiver(), intentFilter); } }

Custom Annotations

You can reduce the repetition in your deep links by creating custom annotations that provide common prefixes that are automatically applied to every class or method annotated with your custom annotation. A popular use case for this is with web versus app deep links:

// Prefix all app deep link URIs with "app://airbnb"
@DeepLinkSpec(prefix = { "app://airbnb" })
@Retention(RetentionPolicy.CLASS)
public @interface AppDeepLink {
  String[] value();
}
// Prefix all web deep links with "http://airbnb.com" and "https://airbnb.com"
@DeepLinkSpec(prefix = { "http://airbnb.com", "https://airbnb.com" })
@Retention(RetentionPolicy.CLASS)
public @interface WebDeepLink {
  String[] value();
}
// This activity is gonna handle the following deep links:
// "app://airbnb/view_users"
// "http://airbnb.com/users"
// "http://airbnb.com/user/{id}"
// "https://airbnb.com/users"
// "https://airbnb.com/user/{id}"
@AppDeepLink({ "/view_users" })
@WebDeepLink({ "/users", "/user/{id}" })
public class CustomPrefixesActivity extends AppCompatActivity {
    //...
}

Usage

Add to your project

build.gradle
file (Latest version is DeeplinkDispatch version ):
groovy
dependencies {
  implementation 'com.airbnb:deeplinkdispatch:x.x.x'
  annotationProcessor 'com.airbnb:deeplinkdispatch-processor:x.x.x'
}

For Kotlin you should use

kapt
instead of
annotationProcessor

Create your deep link module(s) (new on DeepLinkDispatch v3). For every class you annotate with

@DeepLinkModule
, DeepLinkDispatch will generate a "Registry" class, which contains a registry of all your
@DeepLink
annotations.
/** This will generate a AppDeepLinkModuleRegistry class */
@DeepLinkModule
public class AppDeepLinkModule {
}

Optional: If your Android application contains multiple modules (eg. separated Android library projects), you'll want to add one

@DeepLinkModule
class for every module in your application, so that DeepLinkDispatch can collect all your annotations in one "Registry" class per module:
/** This will generate a LibraryDeepLinkModuleRegistry class */
@DeepLinkModule
public class LibraryDeepLinkModule {
}

Create any

Activity
(eg.
DeepLinkActivity
) with the scheme you'd like to handle in your
AndroidManifest.xml
file (using
foo
as an example):
    
        
        
        
        
    

Annotate your

DeepLinkActivity
with
@DeepLinkHandler
and provide it a list of
@DeepLinkModule
annotated class(es):
@DeepLinkHandler({ AppDeepLinkModule.class, LibraryDeepLinkModule.class })
public class DeepLinkActivity extends Activity {
  @Override protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    // DeepLinkDelegate, LibraryDeepLinkModuleRegistry and AppDeepLinkModuleRegistry
    // are generated at compile-time.
    DeepLinkDelegate deepLinkDelegate = 
        new DeepLinkDelegate(new AppDeepLinkModuleRegistry(), new LibraryDeepLinkModuleRegistry());
    // Delegate the deep link handling to DeepLinkDispatch. 
    // It will start the correct Activity based on the incoming Intent URI
    deepLinkDelegate.dispatchFrom(this);
    // Finish this Activity since the correct one has been just started
    finish();
  }
}

of

@DeepLinkHandler({ AppDeepLinkModule.class, LibraryDeepLinkModule.class })
public class DeepLinkActivity extends Activity {
  @Override protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    // Configure a map for configurable placeholders if you are using any. If you do a mapping
    // has to be provided for that are used
    Map configurablePlaceholdersMap = new HashMap();
    configurablePlaceholdersMap.put("your_values", "what should match");
    // DeepLinkDelegate, LibraryDeepLinkModuleRegistry and AppDeepLinkModuleRegistry
    // are generated at compile-time.
    DeepLinkDelegate deepLinkDelegate = 
        new DeepLinkDelegate(new AppDeepLinkModuleRegistry(), new LibraryDeepLinkModuleRegistry(), configurablePlaceholdersMap);
    // Delegate the deep link handling to DeepLinkDispatch. 
    // It will start the correct Activity based on the incoming Intent URI
    deepLinkDelegate.dispatchFrom(this);
    // Finish this Activity since the correct one has been just started
    finish();
  }
}

if you use configurable path segments

Upgrading

When upgrading to 5.x+ you may experience some breaking API changes. Read about them here.

Incremental annotation processing

You must update your build.gradle to opt into incremental annotation processing. When enabled, all custom deep link annotations must be registered in the build.gradle (comma separated), otherwise they will be silently ignored.

Examples of this configuration are as follows:

Standard

groovy
javaCompileOptions {
  annotationProcessorOptions {
    arguments = [
      'deepLink.incremental': 'true',
      'deepLink.customAnnotations': 'com.airbnb.AppDeepLink,com.airbnb.WebDeepLink'
    ]
  }
}

Kotlin kapt

groovy
kapt {
  arguments {
    arg("deepLink.incremental", "true")
    arg("deepLink.customAnnotations", "com.airbnb.AppDeepLink,com.airbnb.WebDeepLink")
  }
}

Performance

Starting with v5 DeeplinkDispatch is designed to be very fast in resolving deep links even if there are a lot of them. To ensure we do not regress from this benchmark tests using

androidx.benchmark
were added.

It is testing the

ScaleTestActivity
in the
sample-benchmarkable-library
which has 2000 deep links. For those on a Pixel 2 running Android 10 we expect the following results:
Started running tests
Timed out waiting for process to appear on google-pixel_2-FA7AW1A04466.
benchmark:        11,520 ns DeeplinkBenchmarks.match1
benchmark:       241,406 ns DeeplinkBenchmarks.match500
benchmark:    12,067,970 ns DeeplinkBenchmarks.newRegistry
benchmark:        12,076 ns DeeplinkBenchmarks.match1000
benchmark:       140,000 ns DeeplinkBenchmarks.match1500
benchmark:       273,230 ns DeeplinkBenchmarks.match2000
benchmark:       148,750 ns DeeplinkBenchmarks.createResultDeeplink1
benchmark:        11,375 ns DeeplinkBenchmarks.parseDeeplinkUrl

Tests ran to completion.

As you can see it taes us about 11ms to create the registry with 2000 entries. A lookup can be done in sub 1ms usually and

createResult
, which includes the lookup for the
match1
case plus actually calling the method that was annotated, can be done in 0.2ms.

The performance tests can be run from Android Studio or via gradle by running

./gradlew sample-benchmark:connectedCheck
(with a device connected). The outoput can be found in
sample-benchmark/build/outputs/connected_android_test_additional_output/
.

Notes

  • Starting with DeepLinkDispatch v3, you have to always provide your own
    Activity
    class and annotate it with
    @DeepLinkHandler
    . It's no longer automatically generated by the annotation processor.
  • Intent filters may only contain a single data element for a URI pattern. Create separate intent filters to capture additional URI patterns.
  • Please refer to the sample app for an example of how to use the library.

Snapshots of the development version are available in Sonatype's

snapshots
repository.

Generated deep links Documentation

You can tell DeepLinkDispatch to generate text a document with all your deep link annotations, which you can use for further processing and/or reference. In order to do that, add to your

build.gradle
file:
groovy
tasks.withType(JavaCompile) {
  options.compilerArgs << "-AdeepLinkDoc.output=${buildDir}/doc/deeplinks.txt"
}

If you are using Kotlin this is how you can enable it for kapt

groovy
kapt {
  arguments {
    arg("deepLinkDoc.output", "${buildDir}/doc/deeplinks.txt")
  }
}

The documentation will be generated in the following format:

* {DeepLink1}\n|#|\n[Description part of javadoc]\n|#|\n{ClassName}#[MethodName]\n|##|\n
* {DeepLink2}\n|#|\n[Description part of javadoc]\n|#|\n{ClassName}#[MethodName]\n|##|\n

You can also generate the output in a much more readable Markdown format by naming the output file

*.md
(e.g.
deeplinks.md
). Make sure that your Markdown viewer understands tables.

Matching and edge cases

Deeplink Dispatchs matching algo is designed to match non ambiguous structured URI style data very fast but because of the supported featureset it comes with some edge cases.

We organize the URI data (of all URIs that are in your app) in a tree structure that is created per module. The URI is dissolved into that tree structure and inserted into that graph at build time. We do not allow duplicates inside the tree at built time and having them will fail the build. However this is currently only guaranteed for each module not across modules.)

Example of a DeeplinkDispagch match graph

At runtime we traverse the graph for each module to find the correct action to undertake. The algo just walks the input URI until the last element and never backtracks inside the graph. The children of each element are checked for matches in alphabetic order:

elements without any variable element -> elements containing placeholders -> elements that are a configurable path segment

Edge cases

  • Duplicates can exist between modules. Only the first one found will be reported as a match. Modules are processed in the order the module registries are listed in your
    DeepLinkDelegate
    creation.
  • Placeholders can lead to duplications at runtime e.g.
    dld://airbnb/dontdupeme
    will match both
    @Deeplink('dld://airbnb/{qualifier}dupeme')
    and
    @Deeplink('dld://airbnb/dontdupeme')
    . They can both be defined in the same module as they are not identical. If they are defined in the same module the algo will match
    @Deeplink('dld://airbnb/dontdupeme')
    as it would check litereal matches before looking at elements containing placeholders. If they are not defined in the same module the one defined in the registry listed first in
    DeeplinkDelegate
    will be matched.
  • Configurable path segments can lead to duplicates. e.g.
    dld://airbnb/obamaos/cereal
    will match both
    @Deeplink('dld://airbnb/obamaos/cereal/')
    and
    @Deeplink('dld://airbnb//cereal')
    if
     is configured to be 
    obamaos
    . The same match rules as mentioned before apply here.
  • Configurable path segments can have empty values e.g.
     can be set to 
    ""
    in the previous example. Which would then match
    dld://airbnb/cereal
    . If a deeplink like that is defined already somewhere else the same match rules as mentioned before apply to which match actually gets found.
  • Because of limitations of the algo the last path element (the item behind the last slash) cannot be a configurable path segment with it's value set to
    ""
    . Currently the system will allow you to do this but will not correctly match in that case.

Proguard Rules

-keep @interface com.airbnb.deeplinkdispatch.DeepLink
-keepclasseswithmembers class * {
    @com.airbnb.deeplinkdispatch.DeepLink ;
}

Note: remember to include Proguard rules to keep Custom annotations you have used, for example by package:

-keep @interface your.package.path.deeplink.
-keepclasseswithmembers class * {
    @your.package.path.deeplink. ;
}

Testing the sample app

Use adb to launch deep links (in the terminal type:

adb shell
).

This fires a standard deep link. Source annotation

@DeepLink("dld://example.com/deepLink")

am start -W -a android.intent.action.VIEW -d "dld://example.com/deepLink" com.airbnb.deeplinkdispatch.sample

This fires a deep link associated with a method, and also passes along a path parameter. Source annotation

@DeepLink("dld://methodDeepLink/{param1}")

am start -W -a android.intent.action.VIEW -d "dld://methodDeepLink/abc123" com.airbnb.deeplinkdispatch.sample

You can include multiple path parameters (also you don't have to include the sample app's package name). Source annotation

@DeepLink("http://example.com/deepLink/{id}/{name}")

am start -W -a android.intent.action.VIEW -d "http://example.com/deepLink/123abc/myname"

Note it is possible to call directly

adb shell am ...
however this seems to miss the URI sometimes so better to call from within shell.

License

Copyright 2015-2020 Airbnb, Inc.

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

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