PlantUML Diagrams in Markdown

PlantUML is a leading component in the text-to-diagram ecosystem. While Mermaid excels on the web, PlantUML provides strict, powerful adherence to UML (Unified Modeling Language) standards.

Using MarkdownToPrettyPDF, you can write PlantUML simply by wrapping it in a plantuml language block.

1. Sequence Diagrams

Sequence diagrams are PlantUML’s most popular feature, offering extensive styling and grouping features impossible in simpler tools.

syntax @startuml actor User participant "First Class" as A participant "Second Class" as B participant "Last Class" as C User -> A: DoWork activate A A -> B: Create Request activate B B -> C: DoWork activate C C --> B: WorkDone destroy C B --> A: Request Created deactivate B A --> User: Done deactivate A @enduml

PlantUML

Notes and Grouping

PlantUML allows you to attach notes alongside lines and create group boxes seamlessly:

syntax @startuml Alice -> Bob : Authentication Request note right of Bob: Bob thinks about it Bob -> Alice : Authentication Response alt successful case Alice -> Bob: Logged in else some kind of failure Alice -> Bob: Authentication Failure end @enduml

PlantUML

2. Class Diagrams

Class diagrams represent the static structure of an application—its classes, methods, and visibility.

Visibility Modifiers

• - private
• # protected
• ~ package private
• + public

Example Class Diagram

syntax @startuml class Dummy { -field1 #field2 ~method1() +method2() } class Flight { flightNumber : Integer departureTime : Date } Flight o-- Airplane : aggregation Flight *-- Passenger : composition Dummy <|-- Flight : inheritance @enduml

PlantUML

3. Use Case Diagrams

Use case diagrams describe the interactions between actors (users or external systems) and the system itself.

syntax @startuml left to right direction actor "Food Critic" as fc rectangle Restaurant { usecase "Eat Food" as UC1 usecase "Pay for Food" as UC2 usecase "Drink" as UC3 } fc --> UC1 fc --> UC2 fc --> UC3 @enduml

PlantUML

Why PlantUML?

PlantUML is extraordinarily mature. It supports state, object, activity, deployment, and Gantt charts. By leveraging the plantuml syntax within Markdown, technical writers can version-control complex system architectures without managing binary image files.