PlantUML mostly does a good job organizing elements and arrows in the resulting diagram. But we can help PlantUML by defining the arrow direction in our PlantUML definition. We can use the keywords up, down, left and right inside the arrow definition.

In the following example we have five rectangles connected with arrows. We define the arrow direction for each arrow.

One of the command line options of Gradle is --offline. With this option we run Gradle in offline mode to indicate we are not connected to network resources like the internet. This could be useful for example if we have defined dependencies in our build script that come from a remote repository, but we cannot access the remote repository, and we still want to run the build. Gradle will use the locally cached dependencies, without checking the remote repository. New dependencies, not already cached, cannot be downloaded of course, so in that scenario we still need a network connection.

We can check in our build script if the --offline command line argument is used. We can use this to disable tasks that depend on network resources so the build will not fail. To see if we invoked our build with the --offline option we can access the property gradle.startParameter.offline. The value is true if the command line argument --offline is used and false if the command line argument is not used.

Gradle added an incubation feature to Gradle 4.6 to add command line options for custom tasks. This means we can run a task using Gradle and add command line options to pass information to the task. Without this feature we would have to use project properties passed via the -P or --project-property. The good thing about the new feature is that the Gradle help task displays extra information about the command line options supported by a custom task.

To add a command line option we simply use the @Option annotation on the setter method of a task property. We must make sure the argument for the setter method is either a boolean, Boolean, String, enum, List<String> or List<enum>. The @Option annotation requires an option argument with the name of the option as it must be entered by the user. Optionally we can add a description property with a description about the option. It is good to add the description, because the help task of Gradle displays this information and helps the user of our custom task.

With the Asciidoctor diagram extension we can include diagrams that are written in plain text. For example PlantUML or Ditaa diagrams. The extension offers a block processor where we include the diagram definitions in our Asciidoctor document. But there is also a block macro processor. With the block macro processor we can refer to an external file. The file is processed and the resulting image is in our output document.

In the following example we see how to use the block macro for a Ditaa diagram:

In our Groovy scripts we can use the @Grab annotation. With this annotation we define dependencies for our script and they will be automatically downloaded and added to the class path when we run our script. When we use IntelliJ IDEA we can use a nice intention that is part of the IntelliJ IDEA Groovy support to download the dependencies from our IDE editor. IDEA downloads the dependencies and add it to the project module dependencies. This is useful, because this will also adds code completion for the classes in the dependency to our editor.

Let’s see this with a little example. We have the following Groovy script in our Groovy project in IntelliJ IDEA:

PlantUML has a built-in icon set we can use in our diagram definitions. The icon set is open source icon set OpenIconic. We refer to an icon using the syntax <&iconName>.We can use an icon everywhere where we can use text in our diagrams.

In the following example we use different icons in different places:

PlantUML supports sprites to be used in diagrams. A sprite is text encoded monochrome graphic we can reference using the syntax <$spriteName>. The sprite is defined using hexadecimal values. We can define a set of hexadecimal values to create our sprite, but we can also generate the correct values from for example a PNG image.

We start with a simple example where we create a small triangle using hexadecimal values:

In a previous post we learned how to use a together block to keep elements together. We can also layout elements in a different way: using hidden lines. We define our elements and by using the keyword [hidden] in our line definition the elements are layout as if there was a line, but we don’t see it. This gives us great flexibility on how we layout our elements.

In the following sample we first have a PlantUML definition where we rely on the default layout:

We have a lot of ways to customize our PlantUML diagrams. We can change the colors and we can even set gradients as color. A gradient has two colors and a direction. The direction of the gradient is set by the separator between the two colors. We can use the following separators to set the gradient direction:

If a class implements the Closeable interface Groovy adds the withCloseable method to the class. The withCloseable method has a closure as argument. The code in the closure is executed and then the implementation of the close method of the Closeable interface is invoked. The Closeable object is passed as argument to the closure, so we can refer to it inside the closure.

In the following example we have two objects that implement the Closeable interface. By using withCloseable we know for sure the close method is invoked after all the code in the closure is executed:

When we define a list in Asciidoctor we usually have a list item that is a paragraph. But if we want to have a block as list item we need to add an extra element to make sure the block is parsed correctly as list item. Because a list item starts with a . or a * at the beginning of a line and a block also is defined on the beginning of the line, we must add the extra element. Together with the list item continuation (+) we can have a list with blocks.

In the following example we define a numbered list with three listing blocks:

PlantUML has some features that come from the underlying software to create diagrams. Graphviz is used by PlantUML and we can use Graphviz features in our PlantUML diagrams. For example we can align multi-line text of labels to be either center (default), left or right aligned using a Graphviz feature. When we want to text to be center aligned we simply use the new-line character \n. If we want to have our text left aligned we use \l instead of \n. And to right align the text we use \r.

In the following example we have three labels that are center, left and right aligned: