oracle/graal · error · NotSerializableException

UnknownKeyException serialization is not supported.

Error message

UnknownKeyException serialization is not supported.

What it means

Error "UnknownKeyException serialization is not supported." thrown in oracle/graal.

Source

Thrown at espresso/src/com.oracle.truffle.espresso.polyglot/src/com/oracle/truffle/espresso/polyglot/UnknownKeyException.java:123

     * <p>
     * In addition a cause may be provided. The cause should only be set if the guest language code
     * caused this problem. An example for this is a language specific proxy mechanism that invokes
     * guest language code to describe an object. If the guest language code fails to execute and
     * this interop exception is a valid interpretation of the error, then the error should be
     * provided as cause.
     *
     * @param unknownKey the key that could not be accessed
     * @param cause the guest language exception that caused the error
     * @since 21.1.0
     */
    @SuppressWarnings("deprecation")
    public static UnknownKeyException create(Object unknownKey, Throwable cause) {
        return new UnknownKeyException(unknownKey, cause);
    }

    @SuppressWarnings({"static-method", "unused"})
    private void writeObject(ObjectOutputStream outputStream) throws IOException {
        throw new NotSerializableException(UnknownKeyException.class.getSimpleName() + " serialization is not supported.");
    }
}

View on GitHub (pinned to a66e9ccd1d)

Solutions

1. Fix the condition reported by the error: UnknownKeyException serialization is not supported.
2. Check the throwing call site and ensure its documented preconditions (argument values, types, environment, or configuration) are satisfied before the call.

Example fix

Validate inputs and environment so that the failing condition does not occur: UnknownKeyException serialization is not supported.

When it happens

Trigger: Thrown at espresso/src/com.oracle.truffle.espresso.polyglot/src/com/oracle/truffle/espresso/polyglot/UnknownKeyException.java:123 when the library encounters an invalid state.

Common situations: Occurs when a caller violates the contract guarded by this check: UnknownKeyException serialization is not supported.

AI-assisted analysis of oracle/graal@a66e9ccd1d (2026-08-14). Data as JSON: /api/errors/03076aafa9593ae2. Report an issue: GitHub.