Quickly Create UML Diagrams in IntelliJ IDEA with PlantUML and Graphviz

Many developers wonder how to draw flowcharts or UML class diagrams; this article introduces the PlantUML plugin for IntelliJ IDEA to quickly create such diagrams.

What is PlantUML

PlantUML is an open‑source project that provides a simple textual language for describing UML relationships and uses the powerful Graphviz rendering engine to generate diagrams, which can be exported as PNG or SVG files.

Advantages of PlantUML

Fully text‑based editing without drag‑and‑drop, automatically adjusts element spacing, and produces clean visuals.

Platform‑independent; any system with the PlantUML JAR can generate diagrams.

Integrates with many editors and IDEs such as IntelliJ IDEA, Eclipse, and Notepad++.

As a Java developer, IntelliJ IDEA is often the preferred IDE, so the following steps focus on using PlantUML within IDEA.

Installing the PlantUML Plugin in IDEA

Navigate to File → Settings → Plugins, search for "PlantUML", locate the "PlantUML integration" entry, and install it.

Installing Graphviz on Windows

Download the installer from the official site:

https://graphviz.gitlab.io/_pages/Download/windows/graphviz-2.38.msi

After installation, configure environment variables:

Add a variable GRAPHVIZ_HOME with the installation path (e.g., D:\WorkWare\Graphviz2.38) and append %GRAPHVIZ_HOME%\bin to the Path variable. Also set GRAPHVIZ_DOT to %GRAPHVIZ_HOME%\bin\dot.exe.

Verify the configuration by opening a Windows command prompt and running dot -version; the version information should be displayed.

Configuring Graphviz in IDEA

Go to File → Settings → Other Settings → PlantUML and set the Graphviz path accordingly.

Using PlantUML to Draw Flowcharts

Create a new .uml file in IDEA and start writing PlantUML code.

Example code:

@startuml
Alice -> Bob: Authentication Request
Bob --> Alice: Authentication Response

Alice -> Bob: Another authentication Request
Alice <-- Bob: another authentication Response
@enduml

The right pane shows a live preview of the diagram.

You can also generate UML class diagrams from existing code.

Other Options

If you prefer not to install Graphviz, you can use the Chrome extension "PlantUML Viewer" to edit PlantUML text directly in the browser and view diagrams instantly.