How To Add A Dependency So That It Is In The Jar With The Mod

David Muir

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29-12-2024

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Adding dependencies directly into a JAR file for modding isn't a standard practice. JAR files are designed to be self-contained units, meaning they ideally include all the necessary classes and resources within their structure. Directly manipulating a JAR's contents after compilation to include external dependencies is generally discouraged due to potential conflicts and difficulties with version management.

Instead of altering the JAR itself, the recommended approach involves utilizing a build system like Maven or Gradle. These systems manage dependencies effectively and automatically include necessary libraries during the compilation and packaging process.

Here's a breakdown of the proper methods for including dependencies when creating a mod:

Using Build Systems (Recommended)

Maven

Maven uses a pom.xml file to define project dependencies. Within this file, you specify the libraries your mod needs. Maven will then download these libraries and incorporate them into the final JAR file during the build process.

Example pom.xml snippet:

<dependencies>
    <dependency>
        <groupId>com.example</groupId>
        <artifactId>my-dependency</artifactId>
        <version>1.0.0</version>
    </dependency>
</dependencies>

After defining your dependencies, run the Maven build command (typically mvn package or mvn install) to create a JAR file containing your mod and its dependencies.

Gradle

Gradle uses a build.gradle (or build.gradle.kts for Kotlin DSL) file to manage dependencies. Similar to Maven, you specify required libraries in this file. Gradle will then download and integrate them into your project's output JAR.

Example build.gradle snippet:

dependencies {
    implementation 'com.example:my-dependency:1.0.0'
}

Run the Gradle build command (usually ./gradlew build or gradlew.bat build) to create a JAR with all dependencies included.

Understanding the Problem with Direct JAR Manipulation

Modifying a JAR file directly (e.g., using tools like WinRAR or 7-Zip to add files) is problematic for several reasons:

• Classpath Issues: The dependency might not be added correctly to the classpath, resulting in ClassNotFoundException errors when your mod runs.
• Manifest Conflicts: Modifying the manifest file improperly can lead to various issues.
• Version Management: Tracking and updating dependencies become extremely difficult.
• Reproducibility: It makes it challenging for others to reproduce your mod's build.

In conclusion: Use a build system like Maven or Gradle for managing dependencies. This method ensures correct classpath setup, simplifies dependency management, and creates clean, reproducible builds. Avoid directly modifying JAR files—it's an unreliable and ultimately inefficient approach.