Guava: ClassPath.getTopLevelClasses() returns empty list.

[jcoeltjen]

Summary
ClassPath.getTopLevelClasses() returns empty list when the path of the classloader contains special characters.

How to reproduce this error

1. Create a packeage with three classes
2. Create the following unit test

    @Test
    public void testMain() throws Exception {
        ClassLoader loader = this.getClass().getClassLoader();
        ClassPath p = ClassPath.from(loader);
        ImmutableSet<ClassPath.ClassInfo> list = p.getTopLevelClasses("testpackage");
        Assert.assertEquals(3, list.size());
    }

1. Copy the whole project to a folder with special characters in its name (like % for example) and execute it.
2. The test will fail. If you copy the project to a folder without special characters in its path the test will pass.

[cpovirk]

@fluentfuture

[ColinChartier]

Looks to be caused by This line

It's caused because URLs automatically encode file names, while the File class expects raw unencoded input.

[cpovirk]

Previously: https://github.com/google/guava/issues/1899

eamonnmcmanus suggested https://weblogs.java.net/blog/kohsuke/archive/2007/04/how_to_convert.html at that point. I'm not sure whether we had a reason for not doing it that way then.

[bjpe]

This bug just caused us to downgrade Guava from 19.0 to 18.0, so we would be delighted if this issue could be fixed.

[kluever]

/cc @cpovirk Any idea who the right owner should be?

[cpovirk]

Besides @fluentfuture, you could try @eamonnmcmanus and @lukesandberg.

[ghost]

@cpovirk The blog you mentioned at https://weblogs.java.net/blog/kohsuke/archive/2007/04/how_to_convert.html has a comment recommending, i.e., Paths.get (entry.toURI ()).toFile () to handle UNC paths on Windows. Any issues with this approach? (Since Guava is migrating to Java 8 anyway...)

[cpovirk]

Hopefully fixed with the commit mentioned above. Please let us know if you still see problems.

[adabir2]

I'm running into this problem in v21.0. Reverting to v18.0 solved the problem. Could you confirm which version the commit mentioned above ended up in, or is expected to be in?

Thanks

[cpovirk]

Sorry, this will be in 22.0.

[UnAfraid]

This problem still exists in java 9

[schackbrian2012]

I am experiencing this issue with Guava 23.0 and Eclipse 4.72. The following code is the simplest example that I could make. But it just returns an empty collection!

import com.google.common.reflect.*;
import java.io.*;

class Test {
    public static void main(String[] args) {
        try {
            System.out.println(ClassPath.from(Test.class.getClassLoader()).getAllClasses());
        } catch (IOException exception) {
            throw new RuntimeException(exception);
        }
    }
}

https://stackoverflow.com/questions/49267460/how-do-i-use-classpathgetallclasses-in-guava

[UnAfraid]

Try with 24.0, it works for me even on java 9

[schackbrian2012]

@UnAfraid Thank you, updating to version 24 worked!

[tuanhiep12]

Im having a similar issue. I have a springboot project. And this block of code:

ClassPath classPath = ClassPath.from(ClassRegistration.class.getClassLoader());
System.out.println(ClassRegistration.class.getPackage().getName());
System.out.println(classPath.getTopLevelClasses(ClassRegistration.class.getPackage().getName()).size());
System.out.println(classPath.getAllClasses().size());

Output is:

com.techx.htsbr.socket.message.receive  
0  
9247  

I can run on intellij successfully. But when I package project to a jar file and run java -jar <filename.jar>, getTopLevelClasses method returns an emty list while getAllClasses method returns non-empty list. I'm using guava version 25.1-jre. same situation in version 19.0.

[devnullpointer]

I'm having the same issue on Android Studio, where the classpath resources is empty hence no top level classes to return.

        final List<Class> classes = new ArrayList<>();

        try
        {
            final ClassPath classPath = ClassPath.from(Thread.currentThread().getContextClassLoader());
            final ImmutableSet<ClassPath.ClassInfo> topLevel = classPath.getTopLevelClasses(PACKAGE_NAME);

            final Collection<Object> classNames = Collections2.transform(topLevel, input -> input.getSimpleName());
            while (classNames.iterator().hasNext())
            {
                final ClassPath.ClassInfo classInfo = (ClassPath.ClassInfo) classNames.iterator().next();
                classes.add(classInfo.getClass());
            }
        }
        catch (final IOException ex)
        {
            Log.e(TAG, "Unable to get classloader.", ex);
        }

[WilliamMin123]

I can’t got it

[dennis-benzinger-hybris]

@tuanhiep12, in your Spring Boot project you probably package your dependency JARs into the main JAR of your application (JAR in JAR) and use the Spring LaunchedURLClassLoader. The problem is that Guava doesn't understand JARs in JARs.

See https://github.com/spring-projects/spring-boot/issues/5338#issuecomment-192327258 for an alternative.

[Blackdread]

Does guava ClassPath class intend to support the spring boot jar layout?