@mermaid-js/mermaid-zenuml

MermaidJS plugin for ZenUML integration - A powerful sequence diagram rendering engine.

A Sequence diagram is an interaction diagram that shows how processes operate with one another and in what order.

Mermaid can render sequence diagrams with ZenUML. Note that ZenUML uses a different syntax than the original Sequence Diagram in mermaid.

zenuml
    BookLibService.Borrow(id) {
      User = Session.GetUser()
      if(User.isActive) {
        try {
          BookRepository.Update(id, onLoan, User)
          receipt = new Receipt(id, dueDate)
        } catch (BookNotFoundException) {
          ErrorService.onException(BookNotFoundException)
        } finally {
          Connection.close()
        }
      }
      return receipt
    }

Installation

With bundlers

npm install @mermaid-js/mermaid-zenuml

import mermaid from 'mermaid';
import zenuml from '@mermaid-js/mermaid-zenuml';

await mermaid.registerExternalDiagrams([zenuml]);

With CDN

<script type="module">
  import mermaid from 'https://cdn.jsdelivr.net/npm/mermaid@11/dist/mermaid.esm.min.mjs';
  import zenuml from 'https://cdn.jsdelivr.net/npm/@mermaid-js/[email protected]/dist/mermaid-zenuml.core.mjs';
  await mermaid.registerExternalDiagrams([zenuml]);
</script>

[!NOTE]
ZenUML uses experimental lazy loading & async rendering features which could change in the future.

Basic Usage

Once the plugin is registered, you can create ZenUML diagrams using the zenuml syntax:

zenuml
    Controller.Get(id) {
        Service.Get(id) {
            item = Repository.Get(id)
            if(item) {
                return item
            } else {
                return null
            }
        }
        return result
    }

ZenUML Syntax Reference

Participants

The participants can be defined implicitly as in the first example on this page. The participants or actors are rendered in order of appearance in the diagram source text. Sometimes you might want to show the participants in a different order than how they appear in the first message. It is possible to specify the actor's order of appearance by doing the following:

zenuml
    title Declare participant (optional)
    Bob
    Alice
    Alice->Bob: Hi Bob
    Bob->Alice: Hi Alice

Annotators

If you specifically want to use symbols instead of just rectangles with text you can do so by using the annotator syntax to declare participants as per below.

zenuml
    title Annotators
    @Actor Alice
    @Database Bob
    Alice->Bob: Hi Bob
    Bob->Alice: Hi Alice

Available annotators include:

• @Actor - Human figure
• @Database - Database symbol
• @Boundary - Boundary symbol
• @Control - Control symbol
• @Entity - Entity symbol
• @Queue - Queue symbol

Aliases

The participants can have a convenient identifier and a descriptive label.

zenuml
    title Aliases
    A as Alice
    J as John
    A->J: Hello John, how are you?
    J->A: Great!

Messages

Messages can be one of:

1. Sync message
2. Async message
3. Creation message
4. Reply message

Sync message

You can think of a sync (blocking) method in a programming language.

zenuml
    title Sync message
    A.SyncMessage
    A.SyncMessage(with, parameters) {
      B.nestedSyncMessage()
    }

Async message

You can think of an async (non-blocking) method in a programming language. Fire an event and forget about it.

zenuml
    title Async message
    Alice->Bob: How are you?

Creation message

We use new keyword to create an object.

zenuml
    new A1
    new A2(with, parameters)

Reply message

There are three ways to express a reply message:

zenuml
    // 1. assign a variable from a sync message.
    a = A.SyncMessage()

    // 1.1. optionally give the variable a type
    SomeType a = A.SyncMessage()

    // 2. use return keyword
    A.SyncMessage() {
    return result
    }

    // 3. use @return or @reply annotator on an async message
    @return
    A->B: result

The third way @return is rarely used, but it is useful when you want to return to one level up.

zenuml
    title Reply message
    Client->A.method() {
      B.method() {
        if(condition) {
          return x1
          // return early
          @return
          A->Client: x11
        }
      }
      return x2
    }

Advanced Features

Nesting

Sync messages and Creation messages are naturally nestable with {}.

zenuml
    A.method() {
      B.nested_sync_method()
      B->C: nested async message
    }

Comments

It is possible to add comments to a sequence diagram with // comment syntax. Comments will be rendered above the messages or fragments. Comments on other places are ignored. Markdown is supported.

zenuml
    // a comment on a participant will not be rendered
    BookService
    // a comment on a message.
    // **Markdown** is supported.
    BookService.getBook()

Loops

It is possible to express loops in a ZenUML diagram. This is done by any of the following notations:

1. while
2. for
3. forEach, foreach
4. loop

while(condition) {
    ...statements...
}

Example:

zenuml
    Alice->John: Hello John, how are you?
    while(true) {
      John->Alice: Great!
    }

Alt (Alternative paths)

It is possible to express alternative paths in a sequence diagram. This is done by the notation

if(condition1) {
    ...statements...
} else if(condition2) {
    ...statements...
} else {
    ...statements...
}

Example:

zenuml
    Alice->Bob: Hello Bob, how are you?
    if(is_sick) {
      Bob->Alice: Not so good :(
    } else {
      Bob->Alice: Feeling fresh like a daisy
    }

Opt (Optional)

It is possible to render an opt fragment. This is done by the notation

opt {
  ...statements...
}

Example:

zenuml
    Alice->Bob: Hello Bob, how are you?
    Bob->Alice: Not so good :(
    opt {
      Bob->Alice: Thanks for asking
    }

Parallel

It is possible to show actions that are happening in parallel.

This is done by the notation

par {
  statement1
  statement2
  statement3
}

Example:

zenuml
    par {
        Alice->Bob: Hello guys!
        Alice->John: Hello guys!
    }

Try/Catch/Finally (Break)

It is possible to indicate a stop of the sequence within the flow (usually used to model exceptions).

This is done by the notation

try {
  ...statements...
} catch {
  ...statements...
} finally {
  ...statements...
}

Example:

zenuml
    try {
      Consumer->API: Book something
      API->BookingService: Start booking process
    } catch {
      API->Consumer: show failure
    } finally {
      API->BookingService: rollback status
    }

Contributing

This package is part of the Mermaid project. See the main repository for contributing guidelines.

Contributors

• Peng Xiao
• Sidharth Vinod
• Dong Cai

License

MIT

Links

• ZenUML Official Website
• Mermaid Documentation
• GitHub Repository