How to Create JAR, WAR, and EAR Files with Gradle

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Gradle is a versatile build automation tool that allows you to create different types of archive files, such as JAR, WAR, and EAR. In this guide, we will walk through the steps to create each of these archive types using Gradle, ensuring that we use the latest dependency versions.

Creating a JAR File

A JAR (Java ARchive) file is used to bundle Java classes and associated metadata and resources into a single file for distribution.

Step 1: Setting Up the Project

Create a new directory for your project and navigate into it:

mkdir gradle-jar-example
cd gradle-jar-example

Initialize a new Gradle project:

gradle init --type java-application

Step 2: Configuring the build.gradle File

Open the build.gradle file and update it as follows:

plugins {
    id 'java'
    id 'application'
}

repositories {
    mavenCentral()
}

dependencies {
    implementation 'org.apache.commons:commons-lang3:3.12.0'
    implementation 'com.google.guava:guava:31.1-jre'
    testImplementation 'org.junit.jupiter:junit-jupiter-api:5.10.0'
    testRuntimeOnly 'org.junit.jupiter:junit-jupiter-engine:5.10.0'
}

application {
    mainClassName = 'com.example.App'
}

test {
    useJUnitPlatform()
}

Step 3: Creating Source Code

Create a simple Java application in src/main/java/com/example/App.java:

package com.example;

public class App {
    public static void main(String[] args) {
        System.out.println("Hello, World!");
    }
}

Step 4: Building the JAR File

To build the JAR file, run:

gradle jar

The JAR file will be created in the build/libs directory.

Creating a WAR File

A WAR (Web Application Archive) file is used to package a web application for deployment on a server.

Step 1: Setting Up the Project

Create a new directory for your project and navigate into it:

mkdir gradle-war-example
cd gradle-war-example

Initialize a new Gradle project:

gradle init --type java-library

Step 2: Configuring the build.gradle File

Open the build.gradle file and update it as follows:

plugins {
    id 'java'
    id 'war'
}

repositories {
    mavenCentral()
}

dependencies {
    implementation 'javax.servlet:javax.servlet-api:4.0.1'
    testImplementation 'org.junit.jupiter:junit-jupiter-api:5.10.0'
    testRuntimeOnly 'org.junit.jupiter:junit-jupiter-engine:5.10.0'
}

war {
    archiveFileName = 'example.war'
}

test {
    useJUnitPlatform()
}

Step 3: Creating a Simple JSP File

Create a simple JSP file in src/main/webapp/index.jsp:

<%@ page contentType="text/html;charset=UTF-8" %>
<html>
<head>
    <title>Hello World</title>
</head>
<body>
    <h1>Hello, World!</h1>
</body>
</html>

Step 4: Building the WAR File

To build the WAR file, run:

gradle war

The WAR file will be created in the build/libs directory.

Step 5: Deploying to Tomcat

To deploy the WAR file to a Tomcat server, follow these steps:

  1. Download Tomcat: Download the latest version of Tomcat from the official website.
  2. Deploy the WAR File: Copy the example.war file to the webapps directory of your Tomcat installation.
  3. Start Tomcat: Start the Tomcat server. The application will be accessible at http://localhost:8080/example.

Creating an EAR File

An EAR (Enterprise Archive) file is used to package multiple JAR and WAR files for deployment on a Java EE server.

Step 1: Setting Up the Project

Create a new directory for your project and navigate into it:

mkdir gradle-ear-example
cd gradle-ear-example

Initialize a new Gradle project:

gradle init --type basic

Step 2: Configuring the build.gradle File

Open the build.gradle file and update it as follows:

plugins {
    id 'java'
    id 'ear'
}

repositories {
    mavenCentral()
}

dependencies {
    deploy project(':jar-module')
    deploy project(':war-module')
}

subprojects {
    apply plugin: 'java'

    repositories {
        mavenCentral()
    }
}

project(':jar-module') {
    dependencies {
        implementation 'org.apache.commons:commons-lang3:3.12.0'
    }
}

project(':war-module') {
    apply plugin: 'war'

    dependencies {
        implementation 'javax.servlet:javax.servlet-api:4.0.1'
    }

    war {
        archiveFileName = 'example.war'
    }
}

ear {
    deploymentDescriptor {
        version = '7'
        applicationName = 'ExampleEAR'
    }
}

Step 3: Creating Subprojects

Create subprojects for the JAR and WAR modules:

  1. JAR Module:

    • Create the directory jar-module/src/main/java/com/example and add a simple Java class.

  2. WAR Module:

    • Create the directory war-module/src/main/webapp and add a simple JSP file.

Step 4: Building the EAR File

To build the EAR file, run:

gradle ear

The EAR file will be created in the build/libs directory.

Conclusion

In this guide, we have covered how to create JAR, WAR, and EAR files using Gradle. We also demonstrated how to set up a simple Java application, a web application with JSP, and an enterprise application with multiple modules. By following these steps, you can effectively package and deploy your Java applications using Gradle.

For more detailed information on Gradle, refer to the Gradle User Guide.

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