Chapter 54. The Application Plugin

Table of Contents

54.1. Usage
54.2. Tasks
54.3. Convention properties

The Application plugin facilitates creating an executable JVM application. It makes it easy to start the application locally during development, and to package the application as a TAR and/or ZIP including operating system specific start scripts.

Applying the Application plugin also implicitly applies the Java plugin. The main source set is effectively the “application”.

Applying the Application plugin also implicitly applies the Distribution plugin. A main distribution is created that packages up the application, including code dependencies and generated start scripts.

54.1. Usage

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

Example 54.1. Using the application plugin

build.gradle

apply plugin: 'application'

The only mandatory configuration for the plugin is the specification of the main class (i.e. entry point) of the application.

Example 54.2. Configure the application main class

build.gradle

mainClassName = "org.gradle.sample.Main"

You can run the application by executing the run task (type: JavaExec). This will compile the main source set, and launch a new JVM with its classes (along with all runtime dependencies) as the classpath and using the specified main class. You can launch the application in debug mode with gradle run --debug-jvm (see JavaExec.setDebug(boolean)).

If your 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.

Example 54.3. Configure default JVM settings

build.gradle

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

54.1.1. The distribution

A distribution of the application can be created, by way of the Distribution plugin (which is automatically applied). A main distribution is created with the following content:

Table 54.1. Distribution content

Location	Content
(root dir)	`src/dist`
`lib`	All runtime dependencies and main source set class files.
`bin`	Start scripts (generated by `createStartScripts` task).

Static files to be added to the distribution can be simply added to src/dist. More advanced customization can be done by configuring the CopySpec exposed by the main distribution.

Example 54.4. Include output from other tasks in the application distribution

build.gradle

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

distributions {
    main {
        contents {
            from(createDocs) {
                into "docs"
            }
        }
    }
}

By specifying that the distribution should include the task’s output files (see Section 19.10.1, “Task 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.

Example 54.5. Automatically creating files for distribution

Output of gradle distZip

> gradle distZip
:createDocs
:compileJava
:processResources NO-SOURCE
:classes
:jar
:startScripts
:distZip

BUILD SUCCESSFUL in 0s
5 actionable tasks: 5 executed

You can run gradle installDist to create an image of the application in build/install/projectName. You can run gradle distZip to create a ZIP containing the distribution, gradle distTar to create an application TAR or gradle assemble to build both.

54.1.2. Customizing start script generation

The application plugin can generate Unix (suitable for Linux, macOS etc.) and Windows start scripts out of the box. The start scripts launch a JVM with the specified settings defined as part of the original build and runtime environment (e.g. JAVA_OPTS env var). The default script templates are based on the same scripts used to launch Gradle itself, that ship as part of a Gradle distribution.

The start scripts are completely customizable. Please refer to the documentation of CreateStartScripts for more details and customization examples.

54.2. Tasks

The Application plugin adds the following tasks to the project.

Table 54.2. Application plugin - tasks

Task name	Depends on	Type	Description
`run`	`classes`	`JavaExec`	Starts the application.
`startScripts`	`jar`	`CreateStartScripts`	Creates OS specific scripts to run the project as a JVM application.
`installDist`	`jar`, `startScripts`	`Sync`	Installs the application into a specified directory.
`distZip`	`jar`, `startScripts`	`Zip`	Creates a full distribution ZIP archive including runtime libraries and OS specific scripts.
`distTar`	`jar`, `startScripts`	`Tar`	Creates a full distribution TAR archive including runtime libraries and OS specific scripts.

54.3. Convention properties

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.