java-native-access/jna · error · RuntimeException

Unexpected registry type {}, expected REG_SZ

Error message

Unexpected registry type {}, expected REG_SZ

What it means

registryGetMultiStringValue sizes the value with RegQueryValueEx and then asserts that the reported type is WinNT.REG_MULTI_SZ; if not, it throws this RuntimeException. The message text says 'expected REG_SZ', but the actual check is against REG_MULTI_SZ - the thrown message is misleading about the expected type. The guard prevents interpreting non multi-string data as a String[].

Source

Thrown at contrib/platform/src/com/sun/jna/platform/win32/Advapi32Util.java:952

     * Get a registry REG_MULTI_SZ value.
     *
     * @param hKey
     *            Parent Key.
     * @param value
     *            Name of the value to retrieve.
     * @return String value.
     */
    public static String[] registryGetStringArray(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_MULTI_SZ) {
            throw new RuntimeException("Unexpected registry type "
                    + lpType.getValue() + ", expected REG_SZ");
        }
                // Allocate enougth memroy to hold value and ensure terminating
                // double NULL chars are present
        Memory data = new Memory(lpcbData.getValue() + 2 * Native.WCHAR_SIZE);
        data.clear();
        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 regMultiSzBufferToStringArray(data);
    }

    /**
     * Convert the null-delimited buffer of strings returned from registry values of
     * type {@link WinNT#REG_MULTI_SZ} to an array of strings.

View on GitHub (pinned to d036ad9781)

Solutions

1. Check the value's type with registryQueryInfoKey or registryGetValue and use the matching typed getter.
2. If the value is a single REG_SZ, use registryGetStringValue and wrap it in a one-element array.
3. Recreate the registry value with type REG_MULTI_SZ (e.g. via PowerShell New-ItemProperty -PropertyType MultiString).
4. Catch RuntimeException and fall back to a single-string read joined into an array.

Example fix

// before
String[] list = Advapi32Util.registryGetMultiStringValue(root, key, "Servers");

// after
Object v = Advapi32Util.registryGetValue(root, key, "Servers");
String[] list = (v instanceof String[])
    ? (String[]) v
    : new String[]{ String.valueOf(v) };

Object v = Advapi32Util.registryGetValue(root, keyPath, valueName);
if (!(v instanceof String[])) throw new IllegalStateException("Expected REG_MULTI_SZ for " + valueName);

boolean isMultiString(Object v) { return v instanceof String[]; }

try { return Advapi32Util.registryGetMultiStringValue(root, key, value); }
catch (RuntimeException e) { log.warn("Value {} is not REG_MULTI_SZ", value); return Collections.emptyList(); }

When it happens

Trigger: Calling Advapi32Util.registryGetMultiStringValue(key, valueName) (or the root/key/value overload) on a registry value whose actual type is anything other than REG_MULTI_SZ, e.g. REG_SZ, REG_EXPAND_SZ or REG_DWORD.

Common situations: A value that once held a multi-string list was replaced by a plain string; documentation assumes REG_MULTI_SZ but the installer writes REG_SZ; copying values between keys via reg export/import changed the type.

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

• Unexpected registry type + lpType.getValue() + , expected RE
• Unexpected registry type {}, expected REG_BINARY
• Unexpected registry type {}, expected REG_DWORD
• Unexpected registry type {}, expected REG_QWORD
• Unexpected registry type + lpType.getValue() + , expected RE

AI-assisted analysis of java-native-access/jna@d036ad9781 (2026-09-12). Data as JSON: /api/errors/3fb50bfe97d5db69. Report an issue: GitHub.