Java.addToClasspath() doesn't allow class resource loading inside of a jar

[Phillipus]

We're accessing a Java plantuml.jar[1] in JS like this:

Java.addToClasspath("path_to/plantuml.jar");

Now we are able to access the classes in this jar.

However, within this jar there are various *.PNG files in a directory, "sprites". The plantuml Java code is loading these image resources from within the jar file like this[2]:

InputStream is = SpriteImage.class.getResourceAsStream(path);

And this is failing, because the resource is not being loaded.

I suspect that Java.addToClasspath() is somehow not sufficient for this. Is there anther setting I need to make so that the resources in the jar can be loaded or is this an issue with how jars are accessed?

[1] https://plantuml.com/download
[2] https://github.com/plantuml/plantuml/blob/master/src/net/sourceforge/plantuml/sprite/SpriteImage.java

[Phillipus]

I extracted the contents of plantuml.jar to a directory plantuml and set the classpath as:

Java.addToClasspath("path_to/plantuml");

and it works perfectly.

So, it's a problem accessing resources within a jar.

[woess]

Thanks for the report. I've been able to reproduce this bug using the following script:

Java.addToClasspath("./plantuml.jar");

var SpriteImage = Java.type("net.sourceforge.plantuml.sprite.SpriteImage");
console.log(SpriteImage.fromInternal("archimate/access"));

This seems to happen when a class is loaded from the same jar while a resource stream is open and still being read, because the streams share state that they shouldn't. This only happens with jar files as you discovered.

[Phillipus]

This seems to happen when a class is loaded from the same jar while a resource stream is open and still being read, because the streams share state that they shouldn't. This only happens with jar files as you discovered.

Yes. Loading the class net.sourceforge.plantuml.security.ImageIO first leads to success:

Java.addToClasspath("./plantuml.jar");
var SpriteImage = Java.type("net.sourceforge.plantuml.sprite.SpriteImage");
var ImageIO = Java.type("net.sourceforge.plantuml.security.ImageIO"); // dummy load of class here
console.log(SpriteImage.fromInternal("archimate/access"));

new SpriteImage(ImageIO.read(is)); is the pain point. Creating a new SpriteImage with ImageIO in the constructor with a stream.

[woess]

Should be fixed now (oracle/graal@9e83f61 @master).
Would be great if you could confirm it with one of the next nightly builds (https://github.com/graalvm/graalvm-ce-dev-builds/releases) (after 20210203 - this version does not have the fix yet).

[Phillipus]

@woess Wow that was quick!

Would be great if you could confirm it with one of the next nightly builds

I will try to do this. However, I'm not sure how to get the particular jar files for my Eclipse-based RCP application. I manually download the following jar files from Maven Central and add them to our plug-in:

graal-sdk-20.3.0.jar
js-20.3.0.jar
js-scriptengine-20.3.0.jar
regex-20.3.0.jar
truffle-api-20.3.0.jar
icu4j-67.1

[Phillipus]

I don't know how to get the correct updated jar files in the list in my previous comment to test this. But I'll add a test case here in case someone can test it.

Requirements:

plantuml.jar [1]
Archimate.puml [2]

JavaScript example:

Java.addToClasspath("./plantuml.jar");

var plantUMLText = "@startuml\n";
plantUMLText += "!include ./Archimate.puml\n";
plantUMLText += "Application_Component(Service, Service)\n";
plantUMLText += "@enduml\n";

var fileOutputStream = new Packages.java.io.FileOutputStream("./PlantUMLDemo.png");
var reader = new Packages.net.sourceforge.plantuml.SourceStringReader(plantUMLText);
console.log("Generation result : " + reader.outputImage(fileOutputStream).getDescription());
fileOutputStream.close();

[1] https://plantuml.com/download
[2] https://github.com/plantuml-stdlib/Archimate-PlantUML/blob/master/Archimate.puml

[Phillipus]

Sorry for the long delay in getting back to this one. I tested the above cases in 22.2 and can confirm the problem is fixed.