Plummy is a CLI tool for automatically running Java image generators (such as PlantUML) in a background daemon, without requiring to restart the JVM on every call. This can significantly speed up static site generation when using such Java tools to process specialized markup.
Each invocation takes at least a few seconds, which makes it painful to use for static site generation, where you may have to process hundreds of UML diagrams at once.
PlantUML server also runs a stable PlantUML instance as daemon, which cuts down the invocation time significantly, but it has many limitations that Plummy is trying to fix:
- PlantUML Server is built as a classic (non-embedded) Java Servlet application, and distributed as a WAR file, so it's far from trivial to setup and requires setting up your own server, complete with a few nice XML files and Web 1.0 era Java EE knowledge. The official docker container makes running PlantUML server a lot simpler, but it's still too heavyweight for what should have been handled by one fat jar file.
- There is no CLI wrapper, so client tools (like site-generators or editor plugins) have to integrate with the server themselves, and each has to be specially set up to know the port where PlantUML is served.
- The user needs to run the server manually and keep track of the server state.
- PlantUML Server does not support external resources very well (e.g. included files, fonts, images)
Mermaid is a Javascript UML diagram generator. It supports a dialect that is similar to PlantUML, but different enough to be incompatible for even the most basic diagrams.
Since mermaid runs on Node.js, invocation start-up times are much faster than running PlantUML directly. Unfortunately, mermaid also lacks many features supported by PlantUML. The lack of advanced styling features, makes it harder to generate clean-looking diagrams for more complex cases.