I've followed "Calling PlantUML from Java" https://plantuml.com/api and that exact example works fine.
However, when I use it to render any C4 .puml file, for some reason, java hangs for about a minute after generation before exiting the java process. In fact, main() is done almost immediately. If I hit "pause" in Intellij, I can see that java is "hanging" in:
which has this signature:
private static native void waitForReferencePendingList();
I've narrowed it down to any .puml file that !include-s a https:// file. (For that, I've created a github gist file containing only a one-line comment)
If main() ends with a System.exit(0), it finishes without the 1 min delay, but I shouldn't have to put System.exit(0) in main() - that is usually implied.
Any ideas on how I can get java to avoid waiting one minute in waitForReferencePendingList? I've tried to look at net.sourceforge.plantuml.Run#main, but there are many other things going on and no clues jumped out at me.
Here is a complete reproducible example, with only minor differences from the API example: The addition of the !includeurl and the println().
String source = "@startuml\n";
source += "!includeurl https://gist.githubusercontent.com/pmorch/acc087c40df50c1877d328c0f0afcdfe/raw/3d8109a3725110ee4762506034404c8ad5029aae/emptyfile.puml\n";
source += "Bob -> Alice : hello\n";
source += "@enduml\n";
SourceStringReader reader = new SourceStringReader(source);
final ByteArrayOutputStream os = new ByteArrayOutputStream();
// Write the first image to "os"
String desc = reader.generateImage(os, new FileFormatOption(FileFormat.SVG));
// The XML is stored into svg
final String svg = new String(os.toByteArray(), Charset.forName("UTF-8"));
System.out.println("Done " + new Date());
I've tried multiple PlantUML versions, at least: