Chapter 45. The Application Plugin

To use the application plugin, include the following in your build script:

apply plugin:'application'

To define the main-class for the application you have to set the mainClassName property as shown below

mainClassName = "org.gradle.sample.Main"

Then, you can run the application by running gradle run. Gradle will take care of building the application classes, along with their runtime dependencies, and starting the application with the correct classpath. You can launch the application in debug mode with gradle run --debug-jvm (see JavaExec.setDebug()).

The plugin can also build a distribution for your application. The distribution will package up the runtime dependencies of the application along with some OS specific start scripts. All files stored in src/dist will be added to the root of the distribution. You can run gradle installApp to create an image of the application in build/install/projectName. You can run gradle distZip to create a ZIP containing the distribution.

If your Java application requires a specific set of JVM settings or system properties, you can configure the applicationDefaultJvmArgs property. These JVM arguments are applied to the run task and also considered in the generated start scripts of your distribution.

applicationDefaultJvmArgs = ["-Dgreeting.language=en"]

The Application plugin adds the following tasks to the project.

The application plugin adds some properties to the project, which you can use to configure its behaviour. See the Project class in the API documentation.

One of the convention properties added by the plugin is applicationDistribution which is a CopySpec. This specification is used by the installApp and distZip tasks as the specification of what is to be included in the distribution. In addition to copying the start scripts to the bin dir and necessary jars to lib in the distribution, all of the files from the src/dist directory are also copied. To include any static files in the distribution, simply arrange them in the src/dist directory.

If your project generates files to be included in the distribution, e.g. documentation, you can add these files to the distribution by adding to the applicationDistribution copy spec.

task createDocs {
    def docs = file("$buildDir/docs")
    outputs.dir docs
    doLast {
        docs.mkdirs()
        new File(docs, "readme.txt").write("Read me!")
    }
}

applicationDistribution.from(createDocs) {
    into "docs"
}

By specifying that the distribution should include the task's output files (see Section 15.9.1, “Declaring a task's inputs and outputs”), Gradle knows that the task that produces the files must be invoked before the distribution can be assembled and will take care of this for you.

> gradle distZip
:createDocs
:compileJava
:processResources UP-TO-DATE
:classes
:jar
:startScripts
:distZip

BUILD SUCCESSFUL

Total time: 1 secs