alibaba/canal · error · IllegalStateException

Extension instance(name: {}, class: {}) could not be instan

Error message

Extension instance(name: {}, class: {})  could not be instantiated: {}

What it means

Error "Extension instance(name: {}, class: {}) could not be instantiated: {}" thrown in alibaba/canal.

Source

Thrown at client-adapter/common/src/main/java/com/alibaba/otter/canal/client/adapter/support/ExtensionLoader.java:177

        return getExtension(cachedDefaultName);
    }

    @SuppressWarnings("unchecked")
    private T createExtension(String name) {
        Class<?> clazz = getExtensionClasses().get(name);
        if (clazz == null) {
            throw new IllegalStateException("Extension instance(name: " + name + ", class: " + type
                                            + ")  could not be instantiated: class could not be found");
        }
        try {
            T instance = (T) EXTENSION_INSTANCES.get(clazz);
            if (instance == null) {
                EXTENSION_INSTANCES.putIfAbsent(clazz, (T) clazz.newInstance());
                instance = (T) EXTENSION_INSTANCES.get(clazz);
            }
            return instance;
        } catch (Throwable t) {
            throw new IllegalStateException("Extension instance(name: " + name + ", class: " + type
                                            + ")  could not be instantiated: " + t.getMessage(),
                t);
        }
    }

    @SuppressWarnings("unchecked")
    private T createExtension(String name, String key) {
        Class<?> clazz = getExtensionClasses().get(name);
        if (clazz == null) {
            throw new IllegalStateException("Extension instance(name: " + name + ", class: " + type
                                            + ")  could not be instantiated: class could not be found");
        }
        try {
            T instance = (T) EXTENSION_KEY_INSTANCE.get(name + "-" + key);
            if (instance == null) {
                EXTENSION_KEY_INSTANCE.putIfAbsent(name + "-" + key, clazz.newInstance());
                instance = (T) EXTENSION_KEY_INSTANCE.get(name + "-" + key);
            }

View on GitHub (pinned to 87be50e876)

Solutions

1. Inspect the instantiation error message; ensure the extension class has a public no-arg constructor and its dependencies are present.
2. Fix classloading conflicts if multiple versions of the adapter jar are on the classpath.

When it happens

Trigger: Thrown at client-adapter/common/src/main/java/com/alibaba/otter/canal/client/adapter/support/ExtensionLoader.java:177 when the library encounters an invalid state.

Common situations: Extension class found but instantiation failed. Require a public no-arg constructor on extensions and propagate the root cause so plugin authors can fix construction errors.

AI-assisted analysis of alibaba/canal@87be50e876 (2026-08-14). Data as JSON: /api/errors/03bcb4facc88984c. Report an issue: GitHub.