We saw many examples in Chapter 3, Managing Task, of adding custom properties to a project using the ext closure. Thus, we will not discuss the topic in this chapter.

Gradle provides a default mechanism of reading the properties file using gradle.properties. You can add the gradle.properties file in any of the following locations:

We will see an example in the next section.

You can define runtime properties on the command line also using the -P and -D options. Using -P, you can define project-specific properties. Using -D, you can define system-level properties. To access system-level properties, you can use System.properties['<propertyname>'].Note that, command line properties override gradle.properties. When you configure properties in multiple places, the following order applies and the last one gets the highest priority:

You might want to use the custom filename for your properties file, for example, login.properties or profile.properties. To use the custom properties, simply read the file using FileInputStream and convert it to the properties object:

task showCustomProp << {
  Properties props = new Properties()
  props.load(new FileInputStream("login.properties"))
  println props
  println props.get('loginKey1')
}

The preceding code will read the login.properties file, and the first println statement will print all the properties while the second println statement will display the value of the loginKey1 property.

Let's take a look at a comprehensive example. We will create one gradle.properties file in the <USER_HOME>/.gradle directory and another gradle.properties file in the project directory:

<USER_HOME>/.gradle/gradle.properties

globalProp1=globalVal1
globalProp2=globalVal2

Chapter6/PropertyExample/Proj1/gradle.properties

Proj1Prop1=Proj1Val1
Proj1Prop2=Proj1Val2
systemProp.sysProp1=sysVal1

Here is our build script, Chapter6/PropertyExample/Proj1/build.gradle:

task showProps << {
  println "local property "+Proj1Prop1
  println "local property "+Proj1Prop2
  println "local property via command line: "+projCommandProp1
  println "global property "+globalProp1
  println "global property "+globalProp2
  println "System property "+System.properties['sysProp1']
  println "System property via command line: "+System.properties['sysCommandProp1']
}

Now, execute the following command:

$gradle -PprojCommandProp1=projCommandVal1-DsysCommandProp1=sysCommandVal1 showProps

:showProps
local property Proj1Val1
local property Proj1Val2
local property via command line: projCommandVal1
global property globalVal1
global property globalVal2
System property sysVal1
System property via command line: sysCommandVal1

BUILD SUCCESSFUL

Here, you can see that the first two lines contain the properties defined in the project's gradle.properties file. The third line shows the property, which the user initialize with the -P option. The fourth and fifth lines show the properties defined in <USER_HOME>/.gradle/gradle.properties. The sixth line shows the system properties defined in the project's gradle.properties file, and finally, the example shows the system property passed in the command line using the -D option.