Guides for SE student projects »

Using PlantUML

The sections below explains how to use PlantUML in a project.

Setting up PlantUML

1. Go to File > Settings to access the Settings page.

2. Go to Settings > Plugins > Marketplace and install the plugin PlantUML integration.

3. Then go to Settings > Languages & Frameworks > PlantUML or search for PlantUML. You can also use a specific version of PlantUML from the releases page.

Creating/editing/exporting diagrams

After installing the PlantUML integration plugin, simply create or open any .puml file to start editing it.

Any changes you make in editor pane on the left will be reflected in the preview pane on the right. However, do take note that these changes will not be reflected in your actual documentation until you export the diagram.

Saving the Diagram as an image

• When using MarkBind as the site generation tool:
  • MarkBind has built-in support for PlantUML. The diagram will be generated and saved as an image automatically. No additional work needed from you. Refer to this section of the MarkBind User Guide for more details.
• When using Jekyll as the site generation tool:
  • The PlantUML integration plugin allows you to export individual diagrams to a location of your choosing. Click the Save Current Diagram Only button and choose the location to export the image file.
  • You will have to git add any new diagrams generated!

Tips and tricks

Maintaining consistency in formatting

It is highly recommended to consistently color your UML diagrams as an visual aid. You can achieve this by creating a dictionary of colors and import it like CSS.

For example, you can create a Style.puml with the contents:

Style.puml.

!define LOGIC_COLOR #3333C4
!define LOGIC_COLOR_T1 #7777DB
!define LOGIC_COLOR_T2 #5252CE
!define LOGIC_COLOR_T3 #1616B0
!define LOGIC_COLOR_T4 #101086

    

    


    
    

Then you can use it in another PlantUML file like this:

UndoSequenceDiagram.puml.

!include Style.puml

box Logic LOGIC_COLOR_T2
participant ":LogicManager" as LogicManager LOGIC_COLOR
participant ":AddressBookParser" as AddressBookParser LOGIC_COLOR
participant ":UndoCommand" as UndoCommand LOGIC_COLOR
end box

    

    


    
    

You can fine-tune the formatting of PlantUML diagrams with the skinparam command. For example, skinparam backgroundColor transparent turns the background of the diagram transparent.

Repositioning elements

While PlantUML’s automatic layout engine usually produces satisfactory results, at times the result can be less than ideal, especially on larger diagrams. Here is an example where the default layout generated by PlantUML has a lot of overlapping lines that are hard to decipher:

Here are some techniques you can use to obtain a more palatable diagram.

Link lengths

By default, a short link (->) points to right and a long link (-->) points downwards. you can extend any link to make it longer (--->).

Link directions

Clever usage of arrow directions will resolve most layout issues. For example, the table below shows how the way in which you specify arrows can results in drastically different layouts for the same diagram.

Table: Link directions

Source	Result
A --> Z B --> Z C --> Z D --> Z A --> 1 B --> 2 C --> 3 D --> 4
'default is down A --> Z 'specify down B -down-> Z 'shorthand for down C -d-> Z 'arrow lengths take priority D -down> Z A -up-> 1 B -up-> 2 C -up-> 3 D -up-> 4
A -up-> Z B -up-> Z C -up-> Z D -up-> Z A --> 1 B --> 2 C --> 3 D --> 4 'Force A B C D A -right[hidden]- B B -right[hidden]- C C -right[hidden]- D

Another technique you can use to influence the layout is to reorder definitions. The layout engine will attempt to order objects in the order in which they are defined. If there is no formal definition, the objects is taken to be declared upon its first usage.

Table: Definition ordering and outcomes

Source	Result
A --> B C --> D
'Class C is defined before A Class C A --> B C --> D
package "Rule Of Thumb";{ Class C A --> B C --> D }

Using reference frames

Reference frames in PlantUML sequence diagrams allow you to group and reuse sequences of interactions, which helps improve readability and reduce repetition in complex scenarios. By encapsulating sequences into reference frames, you can also reduce complexity, making it easier to manage and understand the overall flow of interactions within your diagrams.

Refer to the following example:

@startuml

hide footbox
skinparam sequenceReferenceBackgroundColor #f7807c

actor Player

participant ":TextUi" as TextUi #EE82EE
participant ":MSLogic" as MSLogic #90EE90

Player -> TextUi : mark x y
TextUi -> MSLogic : markCellAt(x, y)
return

TextUi -> MSLogic : getAppearanceOfCellAt(x, y)
MSLogic -> TextUi : getConfig()
TextUi --> MSLogic : config
MSLogic --> TextUi : cellAppearance

TextUi --> Player : Show updated minefield

@enduml

    

    


    
    

The sequence diagram illustrates two main actions: marking a cell and retrieving its appearance. We can simplify the diagram by moving the latter into a new reference frame.

First we update the original diagram as follows:

@startuml

hide footbox
skinparam sequenceReferenceBackgroundColor #f7807c

actor Player

participant ":TextUi" as TextUi #EE82EE
participant ":MSLogic" as MSLogic #90EE90

Player -> TextUi : mark x y
TextUi -> MSLogic : markCellAt(x, y)
return

ref over TextUi, MSLogic
    get minefield appearance
end ref

TextUi --> Player : Show updated minefield

@enduml

    

    


    
    

Then, we create a new diagram for the reference frame.

@startuml

hide footbox

participant ":TextUi" as TextUi #EE82EE
participant ":MSLogic" as MSLogic #90EE90

group sd get minefield appearance
    TextUi -> MSLogic : getAppearanceOfCellAt(x, y)
    MSLogic -> TextUi : getConfig()
    TextUi --> MSLogic : config
    MSLogic --> TextUi : cellAppearance
end

@enduml

    

    


    
    

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Authors:

• Initial Version: Jeffry Lum
• Contributors:
  • MUHAMMAD FIKRI BIN ABDUL KALAM (@mfjkri): added the part on SD reference frames