quarkusio/quarkus · error · RuntimeException

You cannot invoke ${method.getName()}() directly on an objec

Error message

You cannot invoke ${method.getName()}() directly on an object returned from the bytecode recorder, you can only pass it back into the recorder as a parameter

What it means

Objects returned from @Record method invocations are not real instances — they are proxies that record the invoked method calls into bytecode for later replay. Calling methods like hashCode/toString (other than the specially handled equals) directly on such a proxy cannot be recorded, so Quarkus throws. The proxy may only be passed back into the recorder as an argument of another recorded call.

Source

Thrown at core/deployment/src/main/java/io/quarkus/deployment/recording/BytecodeRecorderImpl.java:1726

                return staticInit;
            }
            if (method.getName().equals("toString")
                    && method.getParameterCount() == 0
                    && method.getReturnType().equals(String.class)) {
                return "Runtime proxy of " + returnType + " with id " + key;
            }
            if (method.getName().equals("hashCode")
                    && method.getParameterCount() == 0
                    && method.getReturnType().equals(int.class)) {
                return System.identityHashCode(proxy);
            }
            if (method.getName().equals("equals")
                    && method.getParameterCount() == 1
                    && method.getParameterTypes()[0] == Object.class
                    && method.getReturnType().equals(boolean.class)) {
                return proxy == args[0];
            }
            throw new RuntimeException(
                    "You cannot invoke " + method.getName()
                            + "() directly on an object returned from the bytecode recorder, you can only pass it back into the recorder as a parameter");
        }
    }

    interface BytecodeInstruction {

    }

    public interface ReturnedProxy {
        String __returned$proxy$key();

        boolean __static$$init();
    }

    static final class StoredMethodCall implements BytecodeInstruction {
        final Class<?> theClass;
        final Method method;

View on GitHub (pinned to e1c734241f)

Solutions

Do not call any methods on the returned proxy except passing it into another recorded recorder call
Exclude the object from logging/debugging code (or use its class name, not the object)
For tests, assert on recorded behavior at runtime rather than on the proxy object

Example fix

// before
System.out.println("got: " + recorder.getThing()); // calls toString
// after
// don't touch the proxy; only pass it on:
otherRecorder.use(recorder.getThing());

Defensive patterns

Strategy: try-catch

Type guard

static boolean isRecorderProxy(Object o) {
    return o != null && Proxy.isProxyClass(o.getClass());
}
// only pass proxies back into recorder calls; never log/store them

Try / catch

try {
    sink.use(recorder.getThing()); // OK: passed back into recorder
} catch (RuntimeException e) {
    if (String.valueOf(e.getMessage()).contains("You cannot invoke")) {
        throw new IllegalStateException("Do not call methods on recorder-returned proxies", e);
    }
    throw e;
}

Prevention

Never log, println, or toString recorder return values
Do not put recorder proxies into HashMaps/HashSets (hashCode is invoked)
Keep recorder return values as opaque handles passed only to other recorded calls

When it happens

Trigger: Logging or debugging a value returned from a recorder-invoked method (accidentally invoking toString()/hashCode()); using the returned object in a Map/Set (which calls hashCode/equals); invoking a business method on it at build time expecting a real result.

Common situations: System.out.println of recorder return values during extension development; storing proxy objects in collections used at build time; assertion failures printing proxies in extension tests.

Related errors

AI-assisted analysis of quarkusio/quarkus@e1c734241f (2026-09-05). Data as JSON: /api/errors/518d88376a8522c2. Report an issue: GitHub.