Saturday, 11 February 2012

PlantUML and NetBeans

If you're looking to integrate PlantUML with Netbeans with Maven, check out my blogpost here.


One of the problems with software designers is that they do not enjoy writing Documentation. I do, but then again, I'm weird.

Now Documentation in the area of Java can be split up into two categories:
  • Javadoc comments, that reside in the Java source code, right where it matters
  • Specs, design documents, etc. which are made when the system is first designed and are then stored on a network drive or (if you're lucky) a version control system. They are never updated, become outdated, and forgotten but are sometimes used to provide new junior designers with a wrong idea of the architecture.
So, ideally, you'd wish to have all the specs on hand in the same fashion as your javadoc, with the hope that any change in the code by dilligent designers is also propagated in the javadoc.6

This is where I find PlantUML1 to be extremely handy.

Installing PlantUML in Netbeans

The following task addition lifted straight from the pages of PlantUML and added to build.xml in the netbeans project.
<!-- task definition -->
<taskdef name="plantuml"
  classpath="plantuml.jar" />

<!-- process ./src files -->
<target depends="javadoc-build" name="build-uml">
    <mkdir dir="${dist.javadoc.dir}/images"/>
    <!-- there is an issue where relative paths do not work -->
    <plantuml output="/home/mrbear/NetBeansProjects/YourProject/${dist.javadoc.dir}/images/" verbose="true">
        <fileset dir="./src">
            <include name="**/*.java" />
            <exclude name="**/*" />
This won't work, as plantuml.jar cannot be found automatically. Once you've downloaded it you can let your project know where it is. A good explanation of this can be found at [3].

Running PlantUML and Javadoc

First of all, we add the uml syntax2 to the javadoc comments.
 * <p>Indicates the different sizes that are possible in the displaying
 * of pictures. BIG being un-scaled.</p>
 * <img src="../../images/ImageSize.png"/>
 * @author maartenl
 * @startuml
 * "java.lang.Enum<ImageSize>" <|-- enum ImageSize
 * ImageSize : +ImageSize BIG
 * ImageSize : +ImageSize LARGE
 * ImageSize : +ImageSize MEDIUM
 * ImageSize : +ImageSize THUMB
 * ImageSize : +getHeight()
 * ImageSize : +getWidth()
 * @enduml

public enum ImageSize

Build the "build-uml" target. It will automatically generate all the javadocs and start off generating uml diagrams. You can do this in the Files explorer in netbeans, right-click on build.xml on toplevel and select the appropriate run target. When the "build-uml" ant target is started in netbeans, the following output is shown:

Starting PlantUML
Nb images generated: 1
BUILD SUCCESSFUL (total time: 0 seconds)

The webpage will look like the image below![5] VoilĂ , uml diagrams!


- Two files have the same name, so they both create the same named image file. And they get copied in the ant task, so only one of them remains!

The easiest solution is to add a filename after the "@startuml" command, to indicate the name of the image. This is especially important if you have two or more diagrams within the same Java file. I found it especially convenient when dealing with UML diagrams in files.

A better solution would be to update the Ant task to take care of this automatically.

- I'm getting "taskdef class net.sourceforge.plantuml.ant.PlantUmlTask cannot be found using the classloader AntClassLoader[]"!

Make sure the plantuml.jar file is reachable in the classpath.

- Auto formatting in Netbeans of my Java source code throws my carefully created UML specs in the Javadoc into disarray!

Yes, while Eclipse has a /* @formatter:on */ editor annotation, I have been unable to find the same in Netbeans.

For now, the only solution I have found it to turn on 'explicit newlines' in formatting of the javadoc comments. You can do this by going in Netbeans to Tools->Options->Editor->Formatting->select Java->Category Comments and turn on "Preserve New Lines".

- The image shows errors, something like the image below.
Dot Executable: /usr/bin/dot
File does not exist
Cannot find Graphviz. You should try



java -jar plantuml.jar -testdot

It means you haven't installed the graphviz4 package that takes care of a lot of rendering.

root@localhost:~# apt-get install graphviz
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following extra packages will be installed:
  libcgraph5 libgvpr1
Suggested packages:
The following NEW packages will be installed:
  graphviz libcgraph5 libgvpr1
0 upgraded, 3 newly installed, 0 to remove and 197 not upgraded.
Need to get 553 kB of archives.
After this operation, 1,741 kB of additional disk space will be used.
Do you want to continue [Y/n]? y
Get:1 natty/main libcgraph5 i386 2.26.3-5ubuntu1 [47.8 kB]
Get:2 natty/main libgvpr1 i386 2.26.3-5ubuntu1 [198 kB]
Get:3 natty/main graphviz i386 2.26.3-5ubuntu1 [307 kB]
Fetched 553 kB in 0s (563 kB/s) 
Selecting previously deselected package libcgraph5.
(Reading database ... 163396 files and directories currently installed.)
Unpacking libcgraph5 (from .../libcgraph5_2.26.3-5ubuntu1_i386.deb) ...
Selecting previously deselected package libgvpr1.
Unpacking libgvpr1 (from .../libgvpr1_2.26.3-5ubuntu1_i386.deb) ...
Selecting previously deselected package graphviz.
Unpacking graphviz (from .../graphviz_2.26.3-5ubuntu1_i386.deb) ...
Processing triggers for man-db ...
Setting up libcgraph5 (2.26.3-5ubuntu1) ...
Setting up libgvpr1 (2.26.3-5ubuntu1) ...
Setting up graphviz (2.26.3-5ubuntu1) ...
Processing triggers for libc-bin ...
ldconfig deferred processing now taking place
Thank the Heavens that I'm still running an old Ubuntu, that downloads the proper (read: old) version of GraphViz. PlantUML, I hear, has issues with the new and improved GraphViz 2.28. 1 2

Unfortunately, I was unable to use a relative path in the output attribute in the build.xml. I hope I can fix this later.

Update: changed ImageSizeEnum to ImageSize. Naming should not contain data type names, according to uncle Bob.

Second Update
: PlantUML according to this now works with the newest Graphviz version.

Third Update: Updated NetBeans javadoc formatting problem with a better solution.


[1] PlantUML
[2] Drawing UML with PlantUML - Language Reference Guide (Version 5737)
[3] NetbeansFAQ
[4] Graphviz
[5] Example
[6] "To keep documentation maintained, it is crucial that it be incorporated in the source program, rather than kept as a separate document ... even high-level language syntax does not at all convey purpose." [DRY principle]
The Mythical Man-Month (Frederick P. Brooks, Jr.)



  2. Do you if it is possible to change to default layout? If I have lot's classes (or packages) depending on each other then the default hierarchical layout is useless ..

    Netbeans used to support UML diagramming with something called organic layout which was fantastic, till some genius at Oracle decided to remove to old (but very good!) UML support.

    Would be nice if PlantUML could recreate this .. I think graphviz has support for this, but I don't know how to tell PlantUML to tell graphviz to use a different layout (if such a parametrization is even possible at the moment).


    1. PlantUML is very inflexible when it comes to creating a specific layout. As far as I know there are limited options to tell if items should be to the left/top/bottom/right of the current item.

      If you do have a large hierarchy, you might wish to split it up into several UML diagrams, or shop for an UML drawing tool instead.

      Sorry 'bout that.

  3. Help I'm stuck in this error:
    ant -f C:\\Users\\Kuma\\Documents\\NetBeansProjects\\myProject clean jar
    Target "javadoc-build" does not exist in the project "myProject". It is used from target "build-uml".

    1. Hmm, don't know what to say. The dependency "javadoc-build" is defined in "/nbproject/build-impl.xml". Can you find it there?

  4. This comment has been removed by the author.

  5. Can netbeans illustrate the class diagrams according to what we write? I know that diagrams schemas are shown or did you use a tool like creately ?