View source for Passing Configuration to a Gradle Build via Custom Environment Variables

=Internal=

* [[Gradle_Variables_and_Properties#Passing_Configuration_to_a_Gradle_Build_via_Custom_Environment_Variables|Gradle Variables and Properties]]
* [[Gradle_Operations#Pass_Configuration_via_Custom_Environment_Variables|Gradle Operations]]

=Overview=

This article describes a generic method to pass configuration to a Gradle build using custom environment variables. This method could prove useful when Gradle builds are executed in containers, as it is the case for [[AWS_CodeBuild_Concepts#Build_Project|AWS CodeBuild builds]].

=Playground=

{{External|https://github.com/ovidiuf/playground/tree/master/gradle/custom-environment-variables}}

=Procedure=

The method consists in defining a [[Gradle_Variables_and_Properties#Extra_Properties|project extra property]] that is initialized with the value of the custom environment variable, or to a default value if the environment variable is not defined. The following code sequence is added to build.gradle, in the [[Gradle_Variables_and_Properties#ext_Closure|ext closure]]:

<syntaxhighlight lang='groovy'>
ext {

    projectExtPropertyInformedByEnvironmentVariable = "default value"

    String s = System.getenv("CUSTOM_ENVIRONMENT_VARIABLE");
    if (s != null) {

        projectExtPropertyInformedByEnvironmentVariable = s;
    }
}
</syntaxhighlight>

The following task displays the property value:

<syntaxhighlight lang='groovy'>
ask display {

    println projectExtPropertyInformedByEnvironmentVariable
}
</syntaxhighlight>

If CUSTOM_ENVIRONMENT_VARIABLE is not set, executing the "display" task results in:

 gradle display
 > Configure project :
 default value
 BUILD SUCCESSFUL in 0s

Setting the environment variable propagates it to the build:

 export CUSTOM_ENVIRONMENT_VARIABLE=BLAH
 gradle display
 > Configure project :
 BLAH
 BUILD SUCCESSFUL in 0s

If you need to stop the build with an error if the environment variable is not found in the environment, see: {{Internal|Stop a Gradle Build with an Error|Stop a Gradle Build with an Error}}