Managing plugins and dependencies

Gradle functionality can be extended using plugins. Here are some plugins commonly used in Java projects.

More info on specific plugins:

• Java -- a built-in plugin that adds Java compilation along with testing and bundling capabilities to a project.
  Application -- a built-in plugin for creating an executable JVM application.
• Checkstyle -- a built-in plugin for using Checkstyle in a project.
• Shadow -- a third-party plugin for creating fat/uber JARs.

The relevant lines for adding the above plugins to the build.gradle are given below:

plugins {
    id 'java'
    id 'application'
    id 'checkstyle'
    id 'com.github.johnrengelman.shadow' version '7.1.2'
}

    

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You can follow the links in the list above to find what tasks are provided by a plugin and how to configure it. For example, run is a task provided by the Application plugin, and you can set the mainClassName (mainClass in some versions) property, to indicate which class should be used as the as the entry point of the application:

application {
    mainClass.set("seedu.duke.Main")
}

    

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Gradle can automate the management of dependencies to third-party libraries too. You just need to add the dependency into the build.gradle file and Gradle will do the rest. For example, to add the Natty (a third-party library used for parsing natural language dates e.g., today), you simply have to add the following line to the dependencies section of the build.gradle file.

implementation group: 'com.joestelmach', name: 'natty', version: '0.13'

    

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Tip: Most third-party libraries specify how to add it as a Gradle dependency (example).

From where does Gradle download dependencies? The public servers Gradle will search to find the specified dependencies are listed in the build.gradle file. e.g.,

repositories {
    mavenCentral()
    maven { url 'https://oss.sonatype.org/content/repositories/snapshots/' }
}

    

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Using Gradle to do some common project activities

Running the application

Run the run task to launch the main class of the application.
e.g. ./gradlew run

Cleaning the project

Run the clean to delete the files created during the previous build tasks (e.g. files in the build folder).
e.g. ./gradlew clean

Running Checkstyle

tasks checkstyleMain and checkstyleTest check if the main code and test code complies with the Checkstyle rules, respectively.
e.g., ./gradlew checkstyleMain checkstyleTest

See our Checkstyle Tutorial for more details.

Running tests

Run the test to run all tests and test-related tasks.
e.g. ./gradlew test

See our JUnit tutorial to find how to use JUnit with Gradle.

Creating JAR files

Run the shadowJar task to create a fat JAR file of the application.
e.g. ./gradlew clean shadowJar

See our JAR tutorial to find more about creating JAR files using Gradle.

Compiling

There is no need to run these Gradle tasks manually as they are called automatically by other relevant Gradle tasks.

• compileJava: Checks whether the project has the required dependencies to compile and run the main program, and download any missing dependencies before compiling the classes.
• compileTestJava: Checks whether the project has the required dependencies to perform testing, and download any missing dependencies before compiling the test classes.

Enabling assertions

To enable assertions when executing Java code, add the following to the build.gradle file.

run {
    enableAssertions = true
}

    

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Resources

• Official Gradle Documentation

Authors:

• Initial Version: Jeffry Lum