JRE vs. JDK, What’s the Difference?

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Understanding Their Roles

  • Java Runtime Environment (JRE) 17:

    • Purpose: Allows you to run Java applications.

    • Components: Includes the Java Virtual Machine (JVM), core libraries, and supporting files.

    • Use Case: Ideal for users who only need to execute existing Java programs.

  • Java Development Kit (JDK) 17:

    • Purpose: Enables you to develop and compile Java applications.

    • Components: Contains everything in the JRE plus development tools like the Java compiler (javac), debuggers, and other utilities.

    • Use Case: Essential for developers or any situation where compiling Java code is necessary.

Why You Need JDK 17 for Paper Spigot

When building a Paper Spigot server, you’re not just running a pre-compiled application—you’re compiling the server from source code using BuildTools.jar. This process requires the Java compiler (javac), which is part of the JDK, not the JRE.

In simpler terms:

  • Running a Java application → JRE is sufficient.

  • Building/Compiling Java source code → JDK is required.

+------------------------------------------+
|                JDK 17                    |
|  +------------------------------------+  |
|  |             JRE 17                 |  |
|  |  (JVM + Core Libraries)            |  |
|  +------------------------------------+  |
|  |  Development Tools (javac, etc.)   |  |
+------------------------------------------+

The JDK encapsulates the JRE and adds tools for development.

Metaphorical Insight: Imagine the JRE as a DVD player—it can play movies (run Java applications) but can’t create them. The JDK is like a filmmaking studio—you have all the equipment to produce, edit, and play movies (develop and run Java applications).

So, What Does This Mean for Your Server Setup?

For Your Paper Spigot Server:

  • Building with BuildTools.jar: Requires JDK 17 because you’re compiling Java source code into bytecode.

  • Running the Server: Technically, once compiled, you could use the JRE 17. However, since the JDK includes the JRE, it’s simpler to keep using the JDK.

 

What's Next?

Now that you understand the importance of the JDK in your setup:

  • Consider Scripting Updates:

    Automate server updates using scripts. Since Paper releases frequent updates, this can save time.

  • Explore Plugin Development:

    With the JDK, you’re set to start creating your own plugins. This can tailor your server experience uniquely.

  • Performance Tuning:

    Use Java arguments to optimize performance. For example, experimenting with garbage collection settings can improve server responsiveness.

Did You Know?

  • OpenJDK vs. Oracle JDK:

    • OpenJDK is open-source and freely available. It’s typically what you get via apt install.

    • Oracle JDK has some commercial features but for your server, OpenJDK 17 is more than adequate.

  • Java 17 Features:

    • Java 17 is an LTS (Long-Term Support) release, meaning it will receive updates for several years, ensuring stability for your server environment.

Going Beyond: Enhancing Your Server

  • Implement a Service Manager:

    Set up your server as a system service using systemd to manage automatic starts and restarts.

  • Monitoring and Logs:

    Utilize tools like screen or tmux for session management and monitor logs with multitail or similar utilities.

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