Adding Aspect to Android

Programming AspectJ with Android

AspectJ is the defacto choice for AOP program. So far I did not see any one trying AOP concept in Android. However, I did read one blog mentioning, it should be possible, hence I tried it.

AspectJ puts in pointcut across code and can execute advices around those pointcuts. The beautify of this is once you compile your java source, you add these pointcuts and advices to your program by injecting them in the byte code (of already generated class files).

Knowing this I knew aspectJ can be used in Android, as dex relies on .class files.

Stage 1- Let Java compile java to .class files

Stage 2- Let AspectJ compiler inject point cuts and advices to the .class files

Stage 3- Let Dex take these new class files and create .dex file.

There you should have AspectJ working for Android applications.

Case Study: Inject Tracing code to existing Android source.

Given the case that we have an existing android project, we want to trace the call graph of each thread (showing depth) and we also want to show the cumulative time for each method.

Step 1: Create an HelloWorld Android Project

Step 2: Add some code, so we can show some call graph

Run the program and you will see this on your android emulator

Also on the DDMS Log you will see

What we want to achieve?

We want to show the call graph for this flow. We know that the flow is this way

At the same time we would like to print the commutative time each method took

We would like to print this call graph by using AOP concepts. We would like to define pointcuts around all methods of all classes in package "com.test" and print these statements there.

Step 3: Add aspectjrt.jar to classpath of android

Step 4: Add Aspect file - Trace.aj

Following is the cut down version of the same Trace.aj file. See the inline comments

Step 5 - Compile using AspectJ

As we mentioned above we want to

1. Compile java to .class files using javac

2. Inject pointcuts and advices in .class files using aspectj compile

3. Compile these injected .class files into .dex file

For this we will use ant.

Here is the ant build.xml which I used to put aspectj compilation step between compile->dex target

Here is a snippet of my build.xml around compile and dex targets

Here is the complete build.xml for your reference

Run on command prompt or through eclipse

$> ant install

You should see following output for ant

Step 6 - Run the APK which has aspectj integrated into it (after ant install)

The log looks like as follows, just as we wanted.

Source Code

1. DOWNLOAD ANDROID PROJECT ZIP

2. CHECKOUT FROM code.google.com

Cheers,

Rohit Ghatol