AndroidAspectExample

Project to show examples of leveraging Aspect-Oriented Programming (AOP) techniques

Aspects are defined in AspectLogging.java and affect MainActivity.java. In order to see that the code has been injected, build the app and check the app/build directory for the ajc-transform.log file which will show which advices have been added to the project during the build process.

If you run the app, the aspects added will simply log when a button is clicked or onCreate happens.

Created as a sample for my article "Aspect-Oriented Programming in Android".

Releases

Please see the GitHub Releases Page for this example if you want to see details for a specific Android Gradle Plugin (AGP) version. Each release version for this sample project will correspond to the same AGP version.

Notes

Important: AGP 9.0.0 and AndroidAspectExample EOL

It seems this project is on its last legs with the introduction of AGP 9.0.0. It shouldn't matter too much since this is just a sample project, but heads up that since AGP will be updating their DSL in 9.0.0 and removing it in the near future, this project will stop working. This is because the underlying Aspect library gradle-aspectj-pipeline-plugin is no longer maintained since 2023 so has not updated to the new DSL.

For now, i.e. at least the first major release of AGP 9, this can be worked around by using the following flag in gradle.properties:

android.newDsl=false

As mentioned below, I do not personally recommend AspectJ anymore but if you still prefer to use it, there do seem to be alternatives out there under active development, such as AndroidAOP. I have not personally vetted that library but it does appear to be pretty active and have a decent amount of stars.

This project will be updated until the newDsl flag is removed after which I will probably archive the project.

Plugin Change

As of v4.1.0, this sample project leverages the following Gradle Plugin for weaving aspects:

gradle-aspectj-pipeline-plugin

Previously, this project was leveraging android-gradle-aspectj. For information on why I made the switch, you might be interested in reading my article "Switching AspectJ Plugins in Android".

Code required using either plugin is the same since they both use the same aspectjrt library under the hood. The only difference is the required plugin setup in our gradle files.

Kotlin 1.5.0 Support

This is more of an issue with AspectJ than this project or even the gradle-aspectj-pipeline-plugin project, but Kotlin code compiled with Kotlin version 1.5.0 now uses invokedynamic to to compile Single Abstract Method functions (see here for information in the documentation). This means that lambdas in Kotlin using this version or above will not be weaved as expected as the compiled bytecode will not be able to be matched by AspectJ pointcuts.

To get around this for now, enable the following in project-level build.gradle files:

kotlinOptions {
    freeCompilerArgs = ["-Xsam-conversions=class"]
}

If you are using a version of Kotlin/AGP where kotlinOptions has been deprecated or removed, you can use the following

kotlin {
    compilerOptions {
        freeCompilerArgs = ["-Xsam-conversions=class"]
    }
}

You can read more about the issue here if interested.

Using newer versions of AspectJ

If you are using AspectJ for some other reason and so want to leverage a different version of the library other than the one suggested by the Ibotta Plugin (1.9.6), which is used to compile the plugin, you can generally do so freely up until version 1.9.21 of the AspectJ Plugin (org.aspectj:aspectjrt).

If you have a minSdk of 25 or lower, 1.9.22 will likely give you problems. My testing seems to indicate that this can be fixed by desugaring.

First, make sure the requisite compile option is set

compileOptions {
    coreLibraryDesugaringEnabled true
}

Then, include the desugaring dependency

coreLibraryDesugaring("com.android.tools:desugar_jdk_libs:2.0.4")

Make sure to update this dependency to latest as required.

Why I don't recommend AOP in 2023

In late January 2023, the AOP plugin that this project uses, gradle-aspectj-pipeline-plugin, indicated that the project would no longer be maintained due to issues with the upcoming AGP 8.0.0 updates removing required APIs. In response, I wrote "Why I Don't Recommend Aspect-Oriented Programming in Android in 2023", an article that explains why I would be hesitant to use AOP in an enterprise application in 2023.

I did do some research and came to the conclusion that the plugin would not be broken by AGP 8.0.0 and as such I will continue updating this sample project (playing both sides??) until the plugin begins to stop working with AGP or Kotlin updates.

That being said, even though I am going to continue updating this sample app for the foreseeable future, I would recommend reading "Why I Don't Recommend Aspect-Oriented Programming in Android in 2023" and really thinking about if you actually need to leverage AOP in your project before continuing on and playing around with the sample project.