OSGI BundleHook Implementation

BundleCacheHook.java

package my.hooks;

import org.eclipse.osgi.internal.hookregistry.ClassLoaderHook;
import org.eclipse.osgi.internal.loader.ModuleClassLoader;
import org.eclipse.osgi.internal.loader.classpath.ClasspathEntry;
import org.eclipse.osgi.internal.loader.classpath.ClasspathManager;
import org.eclipse.osgi.internal.loader.classpath.FragmentClasspath;
import org.eclipse.osgi.storage.bundlefile.BundleFile;

import java.util.Enumeration;
import java.util.HashMap;
import java.util.Map;
import java.util.function.Supplier;

/**
 * Hook to scan each bundle and build a caching layer around the entries in the bundle and its ClasspathEntry.
 */
public class BundleCacheHook extends ClassLoaderHook {

    private Map<String, BundleCache> bundleCaches;
    private Supplier<BundleCache> bundleCacheSupplier;

    BundleCacheHook(Supplier<BundleCache> cacheSupplier) {
        bundleCaches = new HashMap<>();
        bundleCacheSupplier = cacheSupplier;
    }

    @Override
    public void classLoaderCreated(ModuleClassLoader classLoader) {
        ClasspathManager classpathManager = classLoader.getClasspathManager();
        BundleCache cache = bundleCaches.computeIfAbsent(
                classLoader.getClasspathManager().getGeneration().getBundleFile().toString(),
                v -> bundleCacheSupplier.get());

        // Scan the host entries first
        for (ClasspathEntry entry : classLoader.getClasspathManager().getHostClasspathEntries()) {
            scanBundle(entry.getBundleFile(), entry, cache);
        }
        // Scan the fragments
        for (FragmentClasspath currentFragment : classpathManager.getFragmentClasspaths()) {
            for (ClasspathEntry entry : currentFragment.getEntries()) {
                scanBundle(entry.getBundleFile(), entry, cache);
            }
        }
    }

    private void scanBundle(BundleFile bundleFile, ClasspathEntry cpEntry, BundleCache cache) {
        // Iterate over the contents of the bundle and populate the cache
        Enumeration<String> entryPaths = bundleFile.getEntryPaths("/", true);
        if (entryPaths != null) {
            while (entryPaths.hasMoreElements()) {
                String path = entryPaths.nextElement();
                cache.put(path, cpEntry);
            }
        }
    }

    @Override
    public ClasspathEntry[] getClassPathEntries(String name, ClasspathManager manager) {
        BundleCache cache = bundleCaches.get(manager.getGeneration().getBundleFile().toString());
        return cache != null ? cache.get(name) : null;
    }

    interface BundleCache {

        ClasspathEntry[] get(String name);

        void put(String name, ClasspathEntry cpEntry);
    }

}