Error in JDK 16 #537
Replies: 13 comments 31 replies
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I've had the same problem: I found this solution |
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Can you please turn on verbose logging (call JDK 16 has started enforcing encapsulation, which is breaking things that use reflection all over the Java ecosystem. However, I tried running all the hundreds of ClassGraph unit tests on JDK 16, and they all pass. So we have to dig deeper to figure out what's going on. Thanks. The issue here is that |
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Logs are too big in this comment. And thanks for trying to help. |
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One issue here (but not the one you're running into) is that should instead be: |
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I think the Whereas in JDK 16, this jar is not on the classpath: And on JDK 16, for this project, the jar So the problem is not a ClassGraph problem (I think??), it appears to be a classpath problem. However if other code in the project is able to see and use the Are you able to provide a minimal reproducer project, please? |
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@worldbiomusic Thank you for the minimal test project! I tried to set up the Paper/Bukkit server, but the program just hangs at |
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@lukehutch Or I can help you with screen sharing using Discord. |
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I have I'm not sure how to do screen sharing via Discord -- what's your username and 4-digit tag suffix? |
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I'm |
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I send friend request. |
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@worldbiomusic OK, I figured out what is going on here... Paper uses the Paperclip library to patch the original server jar. It then adds the patched jar to the classpath in a very weird way, by using a Java agent, and by calling This causes (by stepping through a native code method) This causes the jar to be added to Unfortunately the JDK 16 implements strong encapsulation of JDK internals, so there is absolutely no way to get the jar that was added to the classpath from this field. (It is possible to launch with the JVM commandline option This use of However, there is a workaround you could use: read the value of the property However, you can't use the That should do the trick... let me know! |
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So if your then you need to derive the following URL (in a cross-platform way, maybe by converting to a then add that URL to ClassGraph by calling After that, your existing code should work, including this classloading code: |
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With Burningwave it works (OpenJDK 64-Bit Server VM 16+36-2231). I obtain only an exception that is not important for your purpose and that will be solved in the next release in september (as a workaround you can put inside the bw-core.jar a burningwave.properties file that must contain this: |
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Sorry, I just wanted to solve the problem one-by-one with no confusion. ResultAs a result, I succeed in registering all paper-bukkit events with burningwave using MANIFEST.MF. Using MANIFEST.MF
Using maven
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To remove console messages you must add to your runtime classpath the burningwave.static.properties file and add inside it this code |
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@JJBRT if this works with @burningwave, then Burningwave must be scanning more than just the classpath, because the patched jar is not even on the classpath, as I illustrated in my earlier comment. So How does Burningwave determine what to scan here? As far as I can see the only path criteria that are given is via |
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(I suspect that you have the patched jar manually added directly to your Burningwave project's classpath, or Burningwave automatically scans all sibling directories of all jars on the classpath, or something...) |
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Burningwave automatically scan the main class path if no path is manually indicated: in this case no path is indicated in the findEvents method so these paths have been automatically scanned (add the following line to the findEvents method to obtain the log below [12:20:28 INFO]: [Bukkit-ClassGraph] [STDOUT] paper-1.17.1-170.jar |
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Hello, I'm Roberto Gentili the main Burningwave Core developer. The method |
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@burningwave Hello Roberto. I'm curious how on earth Burningwave Core is able to find the patched jar ( More generally, how does Burningwave Core actually find the classpath entries? Just In the example project by @worldbiomusic, the only jar in |
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@worldbiomusic here's some example code that might solve your problem with ClassGraph. (I'm still waiting for @burningwave to respond explaining how Burningwave Core is able to find the patched jar, but as far as I can determine, something like the following is absolutely required in this case to find the classes in the patched jar, since it's not on the normal classpath.) List<URL> cachedDirJarURLs = new ArrayList<>();
for (String cpEntry : System.getProperty("java.class.path").split(File.pathSeparator)) {
File cpFile = new File(cpEntry);
if (cpFile.canRead()) {
File cachedDir = new File(cpFile.isDirectory() ? cpFile : cpFile.getParentFile(), "cached");
if (cachedDir.canRead() && cachedDir.isDirectory()) {
try {
for (File cachedDirJar : cachedDir.listFiles()) {
if (cachedDirJar.getName().toLowerCase().endsWith(".jar")) {
cachedDirJarURLs.add(cachedDirJar.toURI().toURL());
}
}
} catch (MalformedURLException e) {
// Ignore
}
}
}
}
ClassGraph classGraph = new ClassGraph();
if (!cachedDirJarURLs.isEmpty()) {
classGraph.addClassLoader(new URLClassLoader(cachedDirJarURLs.toArray(new URL[0])));
} |
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@burningwave on your "read the opinion of authoritative people": keilw is a Java expert, but in his comment here he clearly has zero experience with classpath scanning -- he has quite obviously just done a Google search to try to figure out what mechanisms are available. This obscure forum response is not something I would call an authoritative source. |
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@burningwave FYI I asked on the JDK mailing list a few days ago to try to get the https://mail.openjdk.java.net/pipermail/core-libs-dev/2021-August/080462.html |
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By the way @burningwave, every one of your wiki pages still has a footer that says "Burningwave core is a fully indipendent, advanced, free and open source Java frameworks building library that contains THE MOST POWERFUL CLASSPATH SCANNER." Well, you can make whatever claims you want, it's your own project, but I don't think the claim is accurate. Even putting that aside, "powerful" is such a vague claim that it's just not helpful. Maybe you can update your claim to say why you think it's the most powerful (is it the fastest? The most flexible? Able to find more classes than any other scanner?), and actually directly compare it with other scanners if you want to issue smack talk like this, rather than just making this unsubstantiated claim? You're misleading potential users if you're making a claim that can't be backed up. https://github.com/burningwave/core/wiki/In-depth-look-to-ClassHunter-and-configuration-guide |
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Some methods in sun.misc.Unsafe used by Burningwave have been removed
As suggested by JJBRT privately I changed the sentence a few days ago out of respect for Classgraph and the other scanning engines. Burningwave Core is open source and you can explore the code to find the answers to all your questions and even if it uses tricks the results it returns are clean, precise and exact |
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You changed it on the front page, but you didn't change it in the footer on all your Wiki pages, such as the one I linked. |
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@worldbiomusic I just thought of something else you could try. Please try the following, without the changes I suggested above for finding the patched jar. Instead just call This will create a placeholder I totally forgot about this mechanism! But this was designed to solve exactly this sort of problem. It should work for superclasses, interfaces, and annotations that are named but not found during the scan. |
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keep in mind that the classloader you are using with Classgraph**: ... Is a new URLClassloader which is not the same Classloader that the server will use to load the classes and therefore events may not be intercepted. And Burningware Core seems to try to find all files. As mentioned here in the official documentation: "If no path will be passed to SearchConfig, the scan will be executed on the paths indicated by the 'paths.hunters.default-search-config.paths' property of the burningwave.properties file that has the following default value": IF YOU NEED TO SCAN ONLY ONE OR SOME JARS YOU MUST SPECIFY IT: Try it and tell us how long it takes and **check also that classes count returned by Classgraph and by Burningwave Core is the same. |
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I know how Classgraph works and as @JJBRT has already told it is faster and leaner than Burningwave Core: in Burningwave Core the initial choice was to create a scan engine based on query through nestable criteria on the native elements of Reflection that would have been used by the class generator (ClassFactory) to search for classes, intelligently, in case of failure during compilation at runtime by parsing the error messages even through nested archive files (zip, jar, war, ear and jmods). Building such engine based on bytecode would have taken a long time so I opted for a Reflection based scan engine. With Burningwave Core I was able to create also a dependencies shrinker also usable as an application adapter (take a look at Burningwave Tools project) |
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@burningwave makes sense, and I agree with you that we need a diversity of tools for different jobs. This is why from the beginning of ClassGraph, I posted a list of alternative libraries that can also scan the classpath, so that right up front people can consider the pros and cons of different scanning solutions. @JJBRT asked me to add Burningwave Core to this list, and I was very happy to do so. https://github.com/classgraph/classgraph#alternatives I'm still curious what you have done differently for JDK 17. What did the JDK team change between JDK 16 and JDK 17 that required a change for Burningwave Core? |
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For the moment I can only tell you that we have a fully functional version of Burningwave Core for both jdk 17 ea and 18 ea (if you have any doubts I can send you test videos) that we have not yet published on github. Unfortunately we are undecided for particular reasons (which I will only be able to tell you privately via skype) whether to publish it with the release of JDK 17 or 18. Also privately I will be able to explain other techniques used by Burningwave |
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@burningwave Sure, I would love to hear what you discovered. As it is, the only classpath entries ClassGraph can't find are the ones directly added to |
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Sorry, I haven't used it in a while. It's luke.hutch, not lukehutch. |
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Followup: @worldbiomusic tested the |
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@JJBRT I spoke with Roberto Gentili (@burningwave) and I am very happy to report I was completely wrong. Roberto is a genius, and he did in fact find a way to achieve what neither I nor anyone else in the Java world has been able to achieve. It's such a subtle and clever trick that I didn't even understand how it worked until he explained the code. He has generously offered to let me use his code in ClassGraph, so ClassGraph will be able to handle this highly unusual corner case (of Java agents extending the classpath). Grazie, Roberto! |
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Thank you so much Luke I am happy to collaborate with you and the Classgraph team :-) |
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Hello
I have used calssgraph library for Minecraft Bukkit API classes without problems.
But after Minecraft 1.17 update forced users to use JDK 8 to 16 and I have this error.
Error
registerAllEventHandler()java code (from Minecraft Spigot Forum)Java code
How can i fix it?
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