Graphviz: Required for most diagram types. Verify with dot -V.
Java: Required runtime. Verify with java -version.
If Graphviz is missing, sequence diagrams still render (they use the built-in lambda renderer), but other diagram types will fail.
Security & Trust Notes
This skill is a local diagram-generation helper. It does not require credentials, account access, production data access, or background automation. It only documents how to write PlantUML source and render it with local Java/Graphviz tooling.
Rendering PlantUML executes the local PlantUML Java jar and, for most non-sequence diagrams, local Graphviz. Treat .puml files as source code: review diagrams before rendering when they come from untrusted input, and render inside a controlled workspace.
Most examples use PlantUML's local stdlib. A few optional icon examples in references/stdlib-guide.md show external !include URLs for AWS/Azure/devicons; those may fetch resources from GitHub at render time. For sensitive/offline environments, mirror icon libraries locally or avoid URL-based includes.
@startuml DiagramName
left to right direction
skinparam packageStyle rectangle
skinparam actorStyle awesome
actor User
actor Admin
rectangle "System Name" {
usecase "Login" as UC1
usecase "Do Something" as UC2
}
User --> UC1
User --> UC2
UC2 .> UC1 : <<include>>
@enduml
Class Diagram
plantuml
@startuml DiagramName
skinparam classAttributeIconSize 0
abstract class Shape {
+ draw(): void
}
class Circle {
- radius: double
}
Shape <|-- Circle
Circle "1" --> "0..*" Point : contains >
@enduml
Sequence Diagram
plantuml
@startuml DiagramName
actor User
participant ":System" as SYS
User -> SYS : request()
activate SYS
SYS --> User : response()
deactivate SYS
alt success
SYS --> User : ok
else failure
SYS --> User : error
end
@enduml
Activity Diagram
plantuml
@startuml DiagramName
start
:Step 1;
if (Condition?) then (yes)
:Step 2a;
else (no)
:Step 2b;
endif
stop
@enduml
@startuml DiagramName
component [Web App] as WA
component [API Server] as API
interface "REST API" as REST
WA -right- REST
REST -right- API
@enduml
Deployment Diagram
plantuml
@startuml DiagramName
node "Web Server" as WS {
component [Web App] as WA
}
node "DB Server" as DB {
database [Database] as D
}
WA ..> D : JDBC
@enduml
C4 Architecture (System Context)
plantuml
@startuml C4Context
!include <C4/C4_Context>
Person(user, "End User", "Uses the system through web/mobile.")
System(sys, "Order System", "Handles ordering, billing, and fulfilment.")
System_Ext(payment, "Payment Gateway", "Third-party PCI processor.")
Rel(user, sys, "Places orders")
Rel(sys, payment, "Processes payments", "HTTPS/JSON")
@enduml
