Is it possible to declare a variable in Gradle usable in Java?

Question

Is it possible to declare a variable in Gradle usable in Java ? Basically I would like to declare some vars in the build.gradle and then getting it (obviously) at build time

Answer 1

None of the above answers gave me any guidelines so I had to spend two hours learning about Groovy Methods.

I wanted be able to go against a production, sandbox and local environment. Because I'm lazy, I only wanted to change the URL at one place. Here is what I came up with:

 flavorDimensions 'environment'
    productFlavors {
        production {
            def SERVER_HOST = "evil-company.com"
            buildConfigField 'String', 'API_HOST', "\"${SERVER_HOST}\""
            buildConfigField 'String', 'API_URL', "\"https://${SERVER_HOST}/api/v1/\""
            buildConfigField 'String', 'WEB_URL', "\"https://${SERVER_HOST}/\""
            dimension 'environment'
        }
        rickard {
            def LOCAL_HOST = "192.168.1.107"
            buildConfigField 'String', 'API_HOST', "\"${LOCAL_HOST}\""
            buildConfigField 'String', 'API_URL', "\"https://${LOCAL_HOST}/api/v1/\""
            buildConfigField 'String', 'WEB_URL', "\"https://${LOCAL_HOST}/\""
            applicationIdSuffix ".dev"
        }
    }

Alternative syntax, because you can only use ${variable} with double quotes in Groovy Methods.

    rickard {
        def LOCAL_HOST = "192.168.1.107"
        buildConfigField 'String', 'API_HOST', '"' + LOCAL_HOST + '"'
        buildConfigField 'String', 'API_URL', '"https://' + LOCAL_HOST + '/api/v1/"'
        buildConfigField 'String', 'WEB_URL', '"https://' + LOCAL_HOST + '"'
        applicationIdSuffix ".dev"
    }

What was hard for me to grasp was that strings needs to be declared as strings surrounded by quotes. Because of that restriction, I couldn't use reference API_HOST directly, which was what I wanted to do in the first place.

Answer 2

How can you insert String result of function into buildConfigField

Here's an example of build date in human-readable format set:

def getDate() {
    return new SimpleDateFormat("dd MMMM yyyy", new Locale("ru")).format(new Date())
}

def buildDate = getDate()

defaultConfig {
    buildConfigField "String", "BUILD_DATE", "\"$buildDate\""
}

Answer 3

You can create build config field overridable via system environment variables during build:

Fallback is used while developing, but you can override the variable when you run the build on Jenkins or another tool.

In your app build.gradle:

buildTypes {
        def serverUrl =  '\"' + (System.getenv("SERVER_URL")?: "http://default.fallback.url.com")+'\"'
        debug{
            buildConfigField "String", "SERVER_URL", serverUrl
        }
        release {
            minifyEnabled true
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
            buildConfigField "String", "SERVER_URL", serverUrl
        }
    } 

The variable will be available as BuildConfig.SERVER_URL.