Maven Shade Plugin: Create Uber-JARs

Maven Shade Plugin: Create Uber-JARs | Generated by AI

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The maven-shade-plugin is a Maven plugin used to create an “uber-JAR” (a single, self-contained JAR file) by combining a project’s compiled code with its dependencies. It’s commonly used in Java projects to package an application and all its required libraries into one executable JAR file, simplifying distribution and deployment.

Key Details:

Group ID: org.apache.maven.plugins (indicates it’s an official Apache Maven plugin).
Artifact ID: maven-shade-plugin (the specific plugin name).
Purpose:
- Shading: Relocates (renames) packages of dependencies to avoid class conflicts (e.g., when multiple libraries use different versions of the same class).
- Packaging: Bundles dependencies into the final JAR, making it standalone.
- Resource Transformation: Can modify resources (e.g., merge configuration files like MANIFEST.MF).
Common Use Cases:
- Creating executable JARs for command-line applications.
- Resolving classpath conflicts in projects with multiple dependencies.
- Simplifying deployment for applications like Spark or Hadoop jobs.
How It Works:
- Configured in the pom.xml file under the <plugins> section.
- During the build process (typically in the package phase), it combines classes and resources, optionally relocates packages, and produces the final JAR.

Example Configuration in pom.xml:

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-shade-plugin</artifactId>
    <version>3.5.0</version> <!-- Use the latest version -->
    <executions>
        <execution>
            <phase>package</phase>
            <goals>
                <goal>shade</goal>
            </goals>
            <configuration>
                <transformers>
                    <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
                        <mainClass>com.example.Main</mainClass>
                    </transformer>
                </transformers>
            </configuration>
        </execution>
    </executions>
</plugin>

This example specifies the main class for an executable JAR and runs the plugin during the package phase.

Key Features:
- Dependency Inclusion: Embeds dependencies into the JAR.
- Package Relocation: Renames packages to avoid conflicts (e.g., com.google.common to shaded.com.google.common).
- Resource Filtering: Merges or transforms resource files.
- Executable JAR: Adds manifest entries to make the JAR executable with java -jar.

When to Use:

When you need a single JAR for easy distribution.
When dealing with dependency conflicts (e.g., different versions of the same library).
For deploying applications to environments where external dependencies are hard to manage.

If you have a specific question about its configuration or use case, let me know!

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