java-native-access/jna · error · Win32Exception

Win32Exception from native GetLastError when GetThreadPriori

Error message

Win32Exception from native GetLastError when GetThreadPriority returned invalid priority

What it means

getCurrentThreadPriority() calls GetThreadPriority on the current thread's pseudo-handle; GetThreadPriority signals failure by returning THREAD_PRIORITY_ERROR_RETURN, which the library detects via isValidThreadPriority() and reports as a Win32Exception built from GetLastError().

Source

Thrown at contrib/platform/src/com/sun/jna/platform/win32/Kernel32Util.java:1313

     */
    public static void setCurrentProcessBackgroundMode(final boolean enable) {
        // Note: PROCESS_MODE_BACKGROUN_{BEGIN,END} only works with the "current" process handle!
        final DWORD dwPriorityClass = enable ? Kernel32.PROCESS_MODE_BACKGROUND_BEGIN : Kernel32.PROCESS_MODE_BACKGROUND_END;
        if (!Kernel32.INSTANCE.SetPriorityClass(Kernel32.INSTANCE.GetCurrentProcess(), dwPriorityClass)) {
            throw new Win32Exception(Kernel32.INSTANCE.GetLastError());
        }
    }

    /**
     * Gets the priority value of the current thread.
     *
     * @return The priority value of the current thread.
     * @throws Win32Exception if an error occurs.
     */
    public static int getCurrentThreadPriority() {
        final int nPriority = Kernel32.INSTANCE.GetThreadPriority(Kernel32.INSTANCE.GetCurrentThread());
        if (!isValidThreadPriority(nPriority)) {
            throw new Win32Exception(Kernel32.INSTANCE.GetLastError());
        }
        return nPriority;
    }

    /**
     * Sets the priority value for the current thread.
     *
     * @param nPriority The priority value for the thread.
     * @throws Win32Exception if an error occurs.
     */
    public static void setCurrentThreadPriority(final int nPriority) {
        if (!isValidThreadPriority(nPriority)) {
            throw new IllegalArgumentException("The given priority value is invalid!");
        }
        if (!Kernel32.INSTANCE.SetThreadPriority(Kernel32.INSTANCE.GetCurrentThread(), nPriority)) {
            throw new Win32Exception(Kernel32.INSTANCE.GetLastError());
        }
    }

View on GitHub (pinned to d036ad9781)

Solutions

Read Win32Exception.getErrorCode() (often ERROR_ACCESS_DENIED = 5) to identify the native cause.
Use the pseudo-handle from Kernel32.INSTANCE.GetCurrentThread(), which normally always succeeds for queries.
Wrap in try-catch with a THREAD_PRIORITY_NORMAL fallback.
Check that no thread library or mocking layer is corrupting the returned priority value.

Example fix

// before
int prio = Kernel32Util.getCurrentThreadPriority();
// after
int prio;
try {
    prio = Kernel32Util.getCurrentThreadPriority();
} catch (Win32Exception e) {
    LOG.warn("Thread priority query failed: " + e.getErrorCode());
    prio = WinBase.THREAD_PRIORITY_NORMAL;
}

Defensive patterns

Strategy: fallback

Validate before calling

if (!Platform.isWindows()) {
    throw new IllegalStateException("getCurrentThreadPriority is Windows-only");
}

Try / catch

int threadPriority;
try {
    threadPriority = Kernel32Util.getCurrentThreadPriority();
} catch (Win32Exception e) {
    log.warn("GetThreadPriority failed ({}), assuming NORMAL", e.getErrorCode());
    threadPriority = WinBase.THREAD_PRIORITY_NORMAL;
}

Prevention

Treat thread priority reads as best-effort with a THREAD_PRIORITY_NORMAL fallback.
Use the current-thread pseudo-handle so query rights are normally satisfied.
Log e.getErrorCode() to spot security contexts that deny thread queries.
Avoid building control flow that depends on successful priority reads.

When it happens

Trigger: Calling Kernel32Util.getCurrentThreadPriority() when GetThreadPriority fails — e.g. the thread handle is invalid or lacks THREAD_QUERY_INFORMATION rights (unusual with the current-thread pseudo-handle, but possible under strict security contexts or mocks).

Common situations: Security-hardened environments stripping thread access rights; native-layer failures; test harnesses forcing GetThreadPriority to return THREAD_PRIORITY_ERROR_RETURN.

Understand the failure class

Background: Permission denied / not authorized / 403 Forbidden: access-control rejections when the caller lacks the required role, grant, or ownership — this error's family across 18 libraries.

Related errors

AI-assisted analysis of java-native-access/jna@d036ad9781 (2026-09-12). Data as JSON: /api/errors/100a01c6d2dd00af. Report an issue: GitHub.