apache/dubbo · error · IllegalArgumentException

hex2bytes: ( len & 1 ) == 1.

Error message

hex2bytes: ( len & 1 ) == 1.

What it means

Thrown by Bytes.hex2bytes(String, int, int) when the length argument is odd (len & 1 == 1). Hex encoding uses two characters per byte, so a valid hex substring must have an even character count. An odd length indicates a malformed/truncated hex string and is rejected as IllegalArgumentException before the conversion loop.

Source

Thrown at dubbo-common/src/main/java/org/apache/dubbo/common/io/Bytes.java:439

     *
     * @param str hex string.
     * @return byte array.
     */
    public static byte[] hex2bytes(String str) {
        return hex2bytes(str, 0, str.length());
    }

    /**
     * from hex string.
     *
     * @param str hex string.
     * @param off offset.
     * @param len length.
     * @return byte array.
     */
    public static byte[] hex2bytes(final String str, final int off, int len) {
        if ((len & 1) == 1) {
            throw new IllegalArgumentException("hex2bytes: ( len & 1 ) == 1.");
        }

        if (off < 0) {
            throw new IndexOutOfBoundsException("hex2bytes: offset < 0, offset is " + off);
        }
        if (len < 0) {
            throw new IndexOutOfBoundsException("hex2bytes: length < 0, length is " + len);
        }
        if (off + len > str.length()) {
            throw new IndexOutOfBoundsException("hex2bytes: offset + length > array length.");
        }

        int num = len / 2, r = off, w = 0;
        byte[] b = new byte[num];
        for (int i = 0; i < num; i++) {
            b[w++] = (byte) (hex(str.charAt(r++)) << 4 | hex(str.charAt(r++)));
        }
        return b;

View on GitHub (pinned to 3a3043227f)

Solutions

1. Validate the hex string length is even before calling hex2bytes, or pad/strip to an even length.
2. Check the source of the hex string for truncation or corruption.
3. Use hex2bytes(String) for the whole string and ensure the full string is even-length.

Example fix

// before
String hex = "abc"; // odd length
byte[] b = Bytes.hex2bytes(hex); // throws [154]

// after
if (hex.length() % 2 != 0) throw new IllegalArgumentException("odd hex length: " + hex);
byte[] b = Bytes.hex2bytes(hex);

if (len % 2 != 0) throw new IllegalArgumentException("odd hex length: " + len);
byte[] b = Bytes.hex2bytes(str, off, len);

When it happens

Trigger: Calling Bytes.hex2bytes(str, off, len) where len is odd. The input hex string region must contain complete byte pairs; an odd length means a nibble is missing. This is the first validation in hex2bytes and is an argument (not index) error.

Common situations: Truncated hex string from a protocol field or log; a copy that dropped the last character; concatenation that produced an odd total; user input hex that was not length-validated.

Related errors

• bytes2hex: offset < 0, offset is {}
• bytes2hex: length < 0, length is {}
• bytes2hex: offset + length > array length.
• hex2bytes: offset < 0, offset is {}
• hex2bytes: length < 0, length is {}

AI-assisted analysis of apache/dubbo@3a3043227f (2026-08-14). Data as JSON: /api/errors/9e44e6e412f35cc2. Report an issue: GitHub.