name.remal.reflection.ClassLoaderUtils Maven / Gradle / Ivy

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package name.remal.reflection;

import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.net.URL;
import java.net.URLClassLoader;

import static name.remal.SneakyThrow.sneakyThrow;

@SuppressWarnings("JavaReflectionMemberAccess")
public class ClassLoaderUtils {

    static class ClassLoaderWrapper extends ClassLoader {
        public ClassLoaderWrapper(@Nonnull ClassLoader classLoader) {
            super(classLoader);
        }

        @Nullable
        public Package getPackageOrNull(@Nonnull String name) {
            return this.getPackage(name);
        }
    }

    @Nullable
    public static Package getPackageOrNull(@Nonnull ClassLoader classLoader, @Nonnull String packageName) {
        return new ClassLoaderWrapper(classLoader).getPackageOrNull(packageName);
    }

    private static final Method ADD_URL_METHOD;

    static {
        try {
            ADD_URL_METHOD = URLClassLoader.class.getDeclaredMethod("addURL", URL.class);
            ADD_URL_METHOD.setAccessible(true);
        } catch (NoSuchMethodException e) {
            throw sneakyThrow(e);
        }
    }

    public static void addURLsToClassLoader(@Nonnull ClassLoader classLoader, @Nonnull URL... urls) {
        if (0 == urls.length) return;

        ClassLoader systemClassLoader = ClassLoader.getSystemClassLoader();
        do {
            if (classLoader instanceof URLClassLoader) {
                synchronized (classLoader) {
                    for (URL url : urls) {
                        try {
                            ADD_URL_METHOD.invoke(classLoader, url);
                        } catch (IllegalAccessException | InvocationTargetException e) {
                            throw sneakyThrow(e);
                        }
                    }
                }
                return;
            }
            if (systemClassLoader == classLoader) break;
            classLoader = classLoader.getParent();
            if (null == classLoader) classLoader = systemClassLoader;
        } while (true);

        throw new IllegalStateException("New URL can't be added to system ClassLoader: " + systemClassLoader);
    }

}