There is a common situation, that multiple tasks depend on the existence of a directory. Of course you can
deal with this by adding a
mkdir
to the beginning of those tasks. But this is kind of bloated. There is a better solution (works only if the
tasks that need the directory have a
dependsOn
relationship):
Example 14.1. Directory creation with mkdir
build.gradle
classesDir = new File('build/classes') task resources << { classesDir.mkdirs() // do something } task compile(dependsOn: 'resources') << { if (classesDir.isDirectory()) { println 'The class directory exists. I can operate' } // do something }
Output of gradle -q compile
> gradle -q compile The class directory exists. I can operate
Gradle offers a variety of ways to add properties to your build. With the -D
command line
option you can pass a system property to the JVM which runs Gradle. The -D
option of the
gradle command has the same effect as the -D
option of the
java command.
You can also directly add properties to your project objects using properties files. You can place a
gradle.properties
file in the Gradle user home directory (defaults to
) or in your project directory. For
multi-project builds you can place USER_HOME
/.gradlegradle.properties
files in any subproject directory.
The properties of the gradle.properties
can be accessed via the project object. The
properties file in the user's home directory has precedence over property files in the project directories.
You can also add properties directly to your project object via the -P
command line option. For more exotic use cases you can even pass properties directly
to the project object via system and environment properties. For example if you run a build on a continuous
integration server where you have no admin rights for the machine. Your build script
needs properties which values should not be seen by others. Therefore you can't use the -P
option. In this case you can add an environment property in the project administration section (invisible to
normal users).
[6]
If the environment property follows the pattern
ORG_GRADLE_PROJECT_
,
propertyName
=somevaluepropertyName
is added to your project object. We also support the same mechanism for
system properties. The only difference is the pattern, which is
org.gradle.project.
.
propertyName
With the gradle.properties
files you can also set system properties. If a property
in such a file has the prefix systemProp.
the property and its value are added to the
system properties, without the prefix.
Example 14.2. Setting properties with a gradle.properties file
gradle.properties
gradlePropertiesProp=gradlePropertiesValue systemPropertiesProp=shouldBeOverWrittenBySystemProp envProjectProp=shouldBeOverWrittenByEnvProp systemProp.system=systemValue
build.gradle
task printProps << {
println commandLineProjectProp
println gradlePropertiesProp
println systemProjectProp
println envProjectProp
println System.properties['system']
}
Output of gradle -q -PcommandLineProjectProp=commandLineProjectPropValue -Dorg.gradle.project.systemProjectProp=systemPropertyValue printProps
> gradle -q -PcommandLineProjectProp=commandLineProjectPropValue -Dorg.gradle.project.systemProjectProp=systemPropertyValue printProps commandLineProjectPropValue gradlePropertiesValue systemPropertyValue envPropertyValue systemValue
You can access a project property in your build script simply by using its name as you would use a
variable. In case this property does not exists, an exception is thrown and the build fails. If your
build script relies on optional properties the user might set for example in a gradle.properties file,
you need to check for existence before you can access them. You can do this by using the method
hasProperty('propertyName')
which returns
true
or false
.
You can configure the current project using an external build script. All of the Gradle build language is available in the external script. You can even apply other scripts from the external script.
Example 14.3. Configuring the project using an external build script
build.gradle
apply from: 'other.gradle'
other.gradle
println "configuring $project" task hello << { println 'hello from other script' }
Output of gradle -q hello
> gradle -q hello configuring root project 'configureProjectUsingScript' hello from other script
You can configure arbitrary objects in the following very readable way.
Example 14.4. Configuring arbitrary objects
build.gradle
task configure << { pos = configure(new java.text.FieldPosition(10)) { beginIndex = 1 endIndex = 5 } println pos.beginIndex println pos.endIndex }
Output of gradle -q configure
> gradle -q configure 1 5
You can also configure arbitrary objects using an external script.
Example 14.5. Configuring arbitrary objects using a script
build.gradle
task configure << { pos = new java.text.FieldPosition(10) // Apply the script apply from: 'other.gradle', to: pos println pos.beginIndex println pos.endIndex }
other.gradle
beginIndex = 1; endIndex = 5;
Output of gradle -q configure
> gradle -q configure 1 5
To improve responsiveness Gradle caches all compiled scripts by default. This includes all build scripts,
initialization scripts, and other scripts. The first time you run a build for a project, Gradle creates a
.gradle
directory in which it puts the compiled script. The next time you run this
build, Gradle uses the compiled script, if the script has not changed since it was compiled. Otherwise the
script gets compiled and the new version is stored in the cache. If you run Gradle with the
--recompile-scripts
option, the cached script is discarded and the script is compiled and stored
in the cache. This way you can force Gradle to rebuild the cache.