Konloch/bytecode-viewer · error · IllegalArgumentException

null key or factory

Error message

null key or factory

What it means

Static guard in AbstractLoaderFactory.register: the loader-factory registry rejects a registration where the key or the factory instance is null. It ensures the FACTORY_CACHE map only ever holds valid key->factory pairs so later lookups (find/unregister) behave predictably.

Source

Thrown at src/main/java/the/bytecode/club/bytecodeviewer/bootloader/loader/AbstractLoaderFactory.java:45

 * @author Bibl (don't ban me pls)
 * @since 21 Jul 2015 00:18:07
 */
public final class AbstractLoaderFactory
{

    private static final String DEFAULT_KEY = "default-factory";
    private static final Map<String, LoaderFactory<?>> FACTORY_CACHE = new HashMap<>();

    public static void register(LoaderFactory<?> factory)
    {
        register(DEFAULT_KEY, factory);
    }

    public static void register(String key, LoaderFactory<?> factory)
    {
        if (key == null || factory == null)
        {
            throw new IllegalArgumentException("null key or factory");
        }

        if (FACTORY_CACHE.containsKey(key))
        {
            throw new IllegalArgumentException("factory already registered with key: " + key);
        }

        FACTORY_CACHE.put(key, factory);
    }

    public static void unregister(String key)
    {
        if (key == null)
        {
            throw new IllegalArgumentException("null key");
        }

        if (!FACTORY_CACHE.containsKey(key))

View on GitHub (pinned to 31430e0033)

Solutions

1. Ensure the key string is non-null (and sensible: non-empty, unique) before calling register.
2. Ensure the LoaderFactory instance is fully constructed before registration; throw at construction time if it cannot be created.
3. Wrap the register call in validation or null-checks on both arguments.
4. Log/collect config errors at startup rather than passing nulls through.

Example fix

// before
register(cfg.get("loaderKey"), maybeFactory);
// after
String key = cfg.get("loaderKey");
if (key != null && maybeFactory != null) register(key, maybeFactory);

if (key == null || key.isEmpty() || factory == null) { throw new IllegalStateException("register needs non-null key and factory"); }
AbstractLoaderFactory.register(key, factory);

boolean isRegistrable(String key, LoaderFactory<?> f) { return key != null && !key.isEmpty() && f != null; }

try { AbstractLoaderFactory.register(key, factory); }
catch (IllegalArgumentException e) {
    if ("null key or factory".equals(e.getMessage())) throw new ConfigException("loader key/factory missing", e);
    throw e;
}

When it happens

Trigger: Calling AbstractLoaderFactory.register(null, factory), register(key, null), or register(null, null), typically because the key was built from an unchecked config value or the factory construction failed upstream and returned null.

Common situations: Building a plugin/extension system where loader keys come from user config files or environment variables that are unset; factory providers returned null instead of throwing during initialization.

Related errors

• null key
• factory already registered with key: ${key}
• factory doesn't key for key: ${key}
• '${codebase}' is not a directory
• Unknown constant pool tag ${tag}

AI-assisted analysis of Konloch/bytecode-viewer@31430e0033 (2026-09-05). Data as JSON: /api/errors/60fc8b4e51c5e8ab. Report an issue: GitHub.