What causes "Unexpected registry type {}, expected REG_QWORD" in java-native-access/jna?

Use registryGetIntValue for REG_DWORD values, or registryGetStringValue + Long.parseLong for string-stored numbers.

java-native-access/jna · error · RuntimeException

Unexpected registry type {}, expected REG_QWORD

Error message

Unexpected registry type {}, expected REG_QWORD

What it means

registryGetLongValue queries the value's type via RegQueryValueEx and throws this RuntimeException if it is not WinNT.REG_QWORD. The guard ensures the returned 64-bit long is only produced from genuine QWORD data. Note the underlying Windows API returns REG_QWORD data as an 8-byte value that the library reads into a LongByReference.

Source

Thrown at contrib/platform/src/com/sun/jna/platform/win32/Advapi32Util.java:1227

     * Get a registry QWORD value.
     *
     * @param hKey
     *            Parent key.
     * @param value
     *            Name of the value to retrieve.
     * @return Integer value.
     */
    public static long registryGetLongValue(HKEY hKey, String value) {
        IntByReference lpcbData = new IntByReference();
        IntByReference lpType = new IntByReference();
        int rc = Advapi32.INSTANCE.RegQueryValueEx(hKey, value, 0,
                lpType, (char[]) null, lpcbData);
        if (rc != W32Errors.ERROR_SUCCESS
                && rc != W32Errors.ERROR_INSUFFICIENT_BUFFER) {
            throw new Win32Exception(rc);
        }
        if (lpType.getValue() != WinNT.REG_QWORD) {
            throw new RuntimeException("Unexpected registry type "
                    + lpType.getValue() + ", expected REG_QWORD");
        }
        LongByReference data = new LongByReference();
        rc = Advapi32.INSTANCE.RegQueryValueEx(hKey, value, 0,
                lpType, data, lpcbData);
        if (rc != W32Errors.ERROR_SUCCESS
                && rc != W32Errors.ERROR_INSUFFICIENT_BUFFER) {
            throw new Win32Exception(rc);
        }
        return data.getValue();
    }

    /**
     * Get a registry value and returns a java object depending on the value
     * type.
     *
     * @param hkKey
     *            Root key.

View on GitHub (pinned to d036ad9781)

Solutions

Use registryGetIntValue for REG_DWORD values, or registryGetStringValue + Long.parseLong for string-stored numbers.
Read via registryGetValue and convert according to the runtime type (Integer vs Long vs String).
Rewrite the value as REG_QWORD if you control the writer (PowerShell -PropertyType QWord).
Catch RuntimeException and fall back to a type-dispatched read.

Example fix

// before
long ts = Advapi32Util.registryGetLongValue(root, key, "LastRun");

// after
Object v = Advapi32Util.registryGetValue(root, key, "LastRun");
long ts = (v instanceof Long) ? (Long) v
    : (v instanceof Integer) ? ((Integer) v).longValue()
    : Long.parseLong(String.valueOf(v));

Defensive patterns

Strategy: validation

Validate before calling

Object v = Advapi32Util.registryGetValue(root, keyPath, valueName);
if (!(v instanceof Long)) throw new IllegalStateException("Expected REG_QWORD for " + valueName);

Type guard

boolean isQword(Object v) { return v instanceof Long; }

Try / catch

try { return Advapi32Util.registryGetLongValue(root, key, value); }
catch (RuntimeException e) {
  Object v = Advapi32Util.registryGetValue(root, key, value);
  return (v instanceof Number) ? ((Number) v).longValue() : Long.parseLong(String.valueOf(v));
}

Prevention

Match the getter width to the stored type (int getter for DWORD, long getter for QWORD)
Write QWORDs with -PropertyType QWord
Coerce strings with Long.parseLong explicitly
Document the expected registry schema per value name

When it happens

Trigger: Calling Advapi32Util.registryGetLongValue(key, valueName) (or root/key/value overload) on a value stored as REG_DWORD, REG_SZ, REG_BINARY or any type other than REG_QWORD.

Common situations: A timestamp or large counter was written by a legacy tool as two REG_DWORDs or as a string; reading a REG_DWORD value with the 64-bit getter; documentation drift where the stored type changed between product versions.

Understand the failure class

Background: Type mismatch errors: IllegalArgumentException, TypeError and type guards across 150 open-source libraries — this error's family across 150 libraries.

Related errors

AI-assisted analysis of java-native-access/jna@d036ad9781 (2026-09-12). Data as JSON: /api/errors/9e2af8d3079380c9. Report an issue: GitHub.