Mendix Java Editor

A lightweight Java editor for Studio Pro that lets you view and make quick edits to Java Action source files without leaving the IDE.

TL;DR: Right-click any Java Action in App Explorer, select “Open in Java Editor”, and view or edit the source code directly in Studio Pro. Ideal for quick inspections and small edits. Download it here to get started.

The Problem

Editing Java Actions in Mendix means switching to an external IDE:

Open Studio Pro
Find your Java Action
Switch to VS Code or IntelliJ
Navigate to the correct .java file
Make your changes
Switch back to Studio Pro
Hope everything compiles

That’s a lot of context switching just to check a parameter mapping or fix a one-liner.

The Solution: Java Editor

A Monaco-powered Java editor that lives inside Studio Pro:

No IDE switching. No file hunting. Just right-click → view → edit → save.

Good to know: The editor does not include a Java Language Server (LSP), so you won’t get compile errors, type checking, or import resolution. Think of it as a convenient viewer with editing capabilities - perfect for inspecting code, tweaking parameters, or making small fixes. For heavy refactoring, you’ll still want a full IDE like IntelliJ or VS Code.

Demo

Download

Requirements:

Mendix Studio Pro 11.6 or higher
Extensibility setting must be enabled (see instructions below)

Download the extension

Studio Pro Version	Download
11.6+	mendix-java.zip

Extract to your project

Extract the zip file to your Mendix project’s extensions folder:


<YourMendixProject>/
└── extensions/
    └── mendix-java/
        ├── main.js
        ├── editor.js
        ├── mendix-java.css
        └── manifest.json

Example path: C:\Users\YourName\Mendix\MyProject-main\extensions\mendix-java\

Enable extensibility (if not already enabled)

In Studio Pro, click Edit → Preferences
Go to the Advanced tab
Under “Extension Development”, check “Start Studio Pro in Extension Development Mode. Requires restart of Studio Pro.”
Click OK
Restart Studio Pro

Load the extension

Option 1: Restart Studio Pro

Close Studio Pro completely
Reopen your project

Option 2: Synchronize App Directory (faster!)

In Studio Pro, go to App → Synchronize App Directory
Wait for synchronization to complete

Start using it

Right-click any Java Action in App Explorer
Select Open in Java Editor
Edit your code and click the Save button to save

What It Does

Feature	Description
Context Menu Integration	Right-click any Java Action to open it in the editor
Monaco Editor	Professional code editing with Java syntax highlighting (VS Code’s engine)
Basic Autocomplete	Word-based suggestions (no LSP/type-aware IntelliSense)
Save Controls	Explicit save via the Save button
Status Bar	Shows file path and save status at a glance
Dark Theme	Matches Studio Pro’s look and feel
Minimap	Quick navigation through larger files
Bracket Matching	Bracket pair colorization for easier reading

How It Works

Architecture


┌─────────────────────────────────────────────────────────────┐
│                     MENDIX STUDIO PRO                       │
├─────────────────────────────────────────────────────────────┤
│  ┌─────────────────┐    ┌─────────────────────────────────┐ │
│  │  App Explorer   │    │        Java Editor Tab          │ │
│  │                 │    │  ┌───────────────────────────┐  │ │
│  │   Modules       │    │  │      Status Bar           │  │ │
│  │   ├─ Java       │    │  │  filepath    [Save] saved │  │ │
│  │   │  Actions  ◄─┼────┼──┤───────────────────────────│  │ │
│  │   │             │    │  │                           │  │ │
│  │   └─ ...        │    │  │   Monaco Editor (Java)    │  │ │
│  │                 │    │  │                           │  │ │
│  └─────────────────┘    │  └───────────────────────────┘  │ │
│                         └─────────────────────────────────┘ │
└─────────────────────────────────────────────────────────────┘

When you right-click a Java Action and select “Open in Java Editor”:

The extension resolves the Java Action’s source file path using the loadUnits() API
A new editor tab opens with the action’s name as the tab title
The file content is loaded via Mendix’s file API
Monaco renders the Java source with full syntax highlighting
Changes are saved back to the project when you click Save

Technology Stack

Package	Purpose
`@mendix/extensions-api`	Studio Pro integration
`@monaco-editor/react`	VS Code’s editor engine
`react` + `tailwindcss`	UI framework and styling

Built with Vite and TypeScript for fast, type-safe development.

Resources

Questions or feedback? Find me on LinkedIn or email me at b.thomsin@gmail.com.