JustEnoughItems (JEI)

JustEnoughItems (JEI) is a Minecraft mod designed for viewing items and recipes. It focuses on stability, performance, and ease of use. Key characteristics include:

• Minimalist focus: Provides only items and recipes.
• Developer-friendly: Offers a clean API for mod developers to integrate with.
• Lightweight: It is not a coremod and has no dependencies other than Forge (or the relevant loader like Fabric/NeoForge).

For detailed technical implementation details, developers should refer to the JEI Developer Wiki.

The mezz.jei.api.runtime package provides access to JEI's runtime-specific features. This API allows developers to interact with the user interface elements that appear during gameplay, such as the JEI GUIs.

Key capabilities include:

• Controlling the JEI filter text.
• Opening the recipe GUI.
• Retrieving items currently displayed in JEI that are positioned under the user's mouse cursor.

A Universal Handler is used when a single handler needs to support every category of recipe rather than being restricted to one. This is the preferred approach for:

• Mods with recipe pattern encoding.
• Automated recipe systems (e.g., Applied Energistics pattern encoding), where any recipe can be encoded easily through a single interface.

Recipe Category Extensions is an opt-in feature that allows plugins to extend existing recipe categories. This is useful when you want other plugins to add or modify recipes within your defined categories.

By default, the vanilla crafting recipe category is already compatible with this system. To extend the vanilla crafting category, implement the IModPlugin.registerVanillaCategoryExtensions method in your plugin.

For most standard machine GUIs, you can use a Basic Handler. You simply need to define:

1. The slots required for the recipe.
2. The slots for the inventory (including the player's inventory).

JEI will automatically generate the handler logic based on these slot definitions.

Recipe Transfer Handlers enable the [+] button functionality in JEI. When a player clicks this button on a recipe, JEI moves the required items from the player's inventory directly into the target crafting area or machine slots.

JEI provides three levels of implementation complexity depending on the requirements of the machine or process being supported:

If your machine requires more than basic slot definitions—such as using ghost slots for crafting or interacting with a massive backend storage system—you must implement the IRecipeTransferHandler interface and register it manually.

Important Implementation Details:

• Networking: Because JEI is a client-side mod, you are responsible for sending your own packets to the server to trigger the transfer.
• Safety: You must handle the logic to ensure items are transferred correctly without being deleted or duplicated.
• Helpers: Use IRecipeTransferHandlerHelper to assist with the implementation details.

The following Minecraft versions are available on Maven but are not receiving updates. Use these versions only if your environment specifically requires them and you accept the lack of maintenance.

Available Unsupported Versions by Minecraft Version:

• 1.21.x: 1.21.10, 1.21.9, 1.21.8, 1.21.7, 1.21.5, 1.21.4
• 1.20.x: 1.20.6, 1.20.4, 1.20.2, 1.20
• 1.19.x: 1.19.4, 1.19.3, 1.19.1, 1.19
• 1.18.x: 1.18.1, 1.18
• 1.17.x: 1.17.1
• 1.16.x: 1.16.4, 1.16.3, 1.16.2, 1.16.1
• 1.15.x: 1.15.2, 1.15.1
• 1.14.x: 1.14.4, 1.14.3, 1.14.2
• 1.13.x: 1.13.2, 1.13
• 1.12.x: 1.12.1

Note that for many versions, multiple loaders (NeoForge, Fabric, or Forge) are available via their respective Maven metadata URLs.