pinpoint-apm/pinpoint · error · PinpointException

transformCallbackClass must be static inner class. class:

Error message

transformCallbackClass must be static inner class. class:

What it means

TransformCallbackChecker.validate enforces that a TransformCallback supplied to TransformTemplate is either a top-level class or, if it is an inner (nested) class, that it is declared static. A non-static inner class cannot be instantiated by the instrumentation layer without an enclosing instance, so a PinpointException is thrown naming the offending class.

Source

Thrown at agent-module/bootstraps/bootstrap-core/src/main/java/com/navercorp/pinpoint/bootstrap/instrument/transformer/TransformCallbackChecker.java:45

public final class TransformCallbackChecker {
    private TransformCallbackChecker() {
    }

    public static void validate(Class<? extends TransformCallback> transformCallbackClass) {
        validate(transformCallbackClass, null);
    }
    public static void validate(Class<? extends TransformCallback> transformCallbackClass, Class<?>[] parameterTypes) {
        Objects.requireNonNull(transformCallbackClass, "transformCallbackClass");

        // check inner class
        final Class<?> enclosingClass = transformCallbackClass.getEnclosingClass();
        if (enclosingClass != null) {
            // inner class state

            // check static class
            int modifiers = transformCallbackClass.getModifiers();
            if (!Modifier.isStatic(modifiers)) {
                throw new PinpointException("transformCallbackClass must be static inner class. class:" + transformCallbackClass.getName());
            }
        }
//        final Method enclosingMethod = transformCallbackClass.getEnclosingMethod();
//        if (enclosingMethod != null) {
//            throw new PinpointException("Local Inner class not support " + transformCallbackClass.getName());
//        }

        try {
            // check default constructor
            transformCallbackClass.getConstructor(parameterTypes);
        } catch (NoSuchMethodException e) {
            throw new PinpointException("constructor not found " + transformCallbackClass.getName(), e);
        }
    }
}

View on GitHub (pinned to 744c3d3075)

Solutions

1. Add the static modifier to the nested TransformCallback class
2. Move the callback to a top-level class instead of nesting it
3. If a local/anonymous class is used, promote it to a named static nested or top-level class

Example fix

// before
class Plugin {
    class MyCallback implements TransformCallback { ... } // non-static inner
}
// after
class Plugin {
    static class MyCallback implements TransformCallback { ... }
}

Class<?> cb = MyCallback.class;
if (cb.getEnclosingClass() != null && !Modifier.isStatic(cb.getModifiers())) {
    throw new IllegalStateException("TransformCallback inner class must be static: " + cb.getName());
}

boolean isValidCallbackClass(Class<?> c) {
    return c.getEnclosingClass() == null || Modifier.isStatic(c.getModifiers());
}

try {
    transformer.transform(name, cb, null, null);
} catch (PinpointException e) {
    if (e.getMessage().startsWith("transformCallbackClass must be static inner class")) {
        logger.error("declare the callback as a static nested or top-level class", e);
    } else { throw e; }
}

When it happens

Trigger: Passing a non-static inner class (an inner class that implicitly holds a reference to its enclosing instance) as the transformCallbackClass argument to TransformTemplate.transform().

Common situations: Defining the TransformCallback as an inner class of a plugin class without the static keyword; refactoring a top-level callback into a nested one and losing static; Kotlin/Java nesting mistakes.

Understand the failure class

Background: "Must be a positive integer", "Invalid value", "Unsupported": the invalid-argument-value error family, when a library rejects the value you pass — this error's family across 35 libraries.

Related errors

• null parameterType not supported
• Invalid time unit provided.
• unsupported type:
• constructor not found
• not found

AI-assisted analysis of pinpoint-apm/pinpoint@744c3d3075 (2026-09-07). Data as JSON: /api/errors/db059ca3abeb6a66. Report an issue: GitHub.