Default value for a $PROPERTY in Gradle

Question

How can I specify a default value for this simple build.gradle script:

println "Hello $build_version" 

So that I don't get the error:

A problem occurred evaluating root project 'hello_gradle'.
> Could not find property '$build_version' on root project 'hello_gradle'.

I tried some of the operators, checking for nulls etc, but I think just the reference to the property makes it fail. I could fix that by always providing the property, but that's less than ideal.

gradle -Pbuild_version=World

Solution 1

if (!project.hasProperty("build_version")) {
    ext.build_version = "1.0"
}

Solution 2

This checks if the property exists and assigns a default value if not:

def build_version=project.properties['build_version'] ?: "nokey"

Solution 3

This worked for me:

def AWS_ACCESS_KEY="nokey"
def AWS_SECRET_KEY="nokey"

if (project.hasProperty("AWS_ACCESS_KEY")) {
    AWS_ACCESS_KEY=project.get("AWS_ACCESS_KEY")
}
if (project.hasProperty("AWS_SECRET_KEY")) {
    AWS_SECRET_KEY=project.get("AWS_SECRET_KEY")
}

Solution 4

Another way to make it short and nice:

ext.buildVersion = project.getProperties().getOrDefault("build_version", "1.0")

Solution 5

Starting from Gradle 2.13:

ext.buildVersion = project.findProperty('build_version') ?: '1.0'

View more solutions