HB Blog 105: Overview Of Build Automation Tools.

Build automation is the process of automating the creation of a software build and the associated processes including: compiling computer source code into binary code, packaging binary code, and running automated tests.

Basically, a build automation was accomplished through makefiles. A makefile is a file that contains a set of directives used with the make build automation tool. Build automation tool are divided into 2 categories namely,

1. Build automation utility: - Whose primary purpose is to generate build artifacts through activities like compiling and linking the source code.
2. Build automation servers: - These are general web based tools that execute build automation utilities on a scheduled or triggered basis; a continuous integration server is a type of build automation server. 

There are various tools that automates the process of compiling computer source code into binary code based on creation of make file.
Make-based tools such as GNU make, make, mk, etc.
Non-Make-based tools such as Apache Ant, Apache Maven, Gradle, etc.

Earlier, we used to use Eclipse for our Android development where, we used dx, aapt, etc. tools for Apk creation. Now, have you ever wondered why the res folder is in the same directory as your src folder? This is where the build system enters the picture. The build system automatically takes all the source files (.java or .xml), then applies the appropriate tool (e.g. takes java class files and converts them to dex files), and groups all of them into one compressed file, our beloved APK. This build system uses some conventions: an example of one is to specify the directory containing the source files (in Eclipse it is \src folder) or resources files (in Eclipse it is \res folder). Now, in order to automate all these tasks, there has to be a script; you can write your own build system using shell scripting in linux or batch files syntax in windows.

Gradle is another build system that takes the best features from other build systems and combines them into one. It is improved based off of their shortcomings. It is a JVM based build system, what that means is that you can write your own script in Java, which Android Studio makes use of. One more thing about gradle is that it is a plugin based system. This means if you have your own programming language and you want to automate the task of building some package (output like a JAR for Java) from sources then you can write a complete plugin in Java or Groovy, and distribute it to rest of world.

Have a look on few code snippets,

//build.gradle 

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apply plugin: 'com.android.application' android { compileSdkVersion 23 buildToolsVersion "23.0.3" defaultConfig { applicationId "com.example.user.myapplication" minSdkVersion 15 targetSdkVersion 23 versionCode 1 versionName "1.0" } buildTypes { release { minifyEnabled false proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro' } } } dependencies { compile fileTree(dir: 'libs', include: ['*.jar']) testCompile 'junit:junit:4.12' compile 'com.android.support:appcompat-v7:23.3.0' }