baomidou/mybatis-plus · error · IllegalArgumentException

Failed to deserialize object

Error message

Failed to deserialize object

What it means

SerializationUtils.deserialize(bytes) reads an object back via ObjectInputStream; any IOException (corrupt bytes, truncated stream, invalid stream header, stream class version mismatch surfaced as InvalidClassException) is rethrown as IllegalArgumentException('Failed to deserialize object'). The data is unusable — this is not a classpath problem (that produces the ClassNotFoundException branch).

Source

Thrown at mybatis-plus-core/src/main/java/com/baomidou/mybatisplus/core/toolkit/SerializationUtils.java:82

            throw new IllegalArgumentException("Failed to serialize object of type: " + object.getClass(), ex);
        }
        return baos.toByteArray();
    }

    /**
     * Deserialize the byte array into an object.
     *
     * @param bytes a serialized object
     * @return the result of deserializing the bytes
     */
    public static Object deserialize(byte[] bytes) {
        if (bytes == null) {
            return null;
        }
        try (ObjectInputStream ois = new ObjectInputStream(new ByteArrayInputStream(bytes))) {
            return ois.readObject();
        } catch (IOException ex) {
            throw new IllegalArgumentException("Failed to deserialize object", ex);
        } catch (ClassNotFoundException ex) {
            throw new IllegalStateException("Failed to deserialize object type", ex);
        }
    }
}

View on GitHub (pinned to bf67d90747)

Solutions

1. Confirm the byte[] actually came from Java serialization — check for the stream header (AC ED 00 05) if reading from storage.
2. Use a binary column type (BLOB/BYTEA/VARBINARY(max)), not TEXT/VARCHAR, for serialized payloads.
3. Declare an explicit private static final long serialVersionUID on serialized classes so structural changes do not invalidate old data.
4. Treat unreadable cached entries as cache misses: delete and regenerate instead of retrying.

Example fix

-- before: serialized bytes stored in TEXT get charset-mangled -> IOException on read
ALTER TABLE doc ADD COLUMN payload TEXT;

-- after: use a binary column
ALTER TABLE doc ADD COLUMN payload BLOB;

if (bytes == null || bytes.length < 4
        || (bytes[0] & 0xFF) != 0xAC || (bytes[1] & 0xFF) != 0xED) {
    // not a Java serialization stream; treat as corrupt/cache miss
}

static boolean looksLikeJavaSerialized(byte[] b) {
    return b != null && b.length > 4
        && (b[0] & 0xFF) == 0xAC && (b[1] & 0xFF) == 0xED
        && (b[2] & 0xFF) == 0x00 && (b[3] & 0xFF) == 0x05;
}

try {
    return SerializationUtils.deserialize(bytes);
} catch (IllegalArgumentException e) {
    log.warn("corrupt serialized entry, evicting and recomputing", e);
    cache.remove(key);
    return recompute(key); // cache-miss style fallback
}

When it happens

Trigger: Feeding deserialize() bytes that are not a valid Java serialization stream: truncated arrays (DB column too short, e.g. VARCHAR vs BLOB), corrupted cache entries after an unclean shutdown, binary-mangled by charset conversion, or data serialized with an incompatible class layout (serialVersionUID or structural change causing InvalidClassException).

Common situations: Storing serialized blobs in a TEXT/VARCHAR column so the driver mangles bytes; changing entity class structure (adding/removing fields) without maintaining serialVersionUID; cache files surviving a crash; reading bytes that were never produced by serialize() (e.g. JSON or protobuf payload).

Related errors

• Failed to serialize object of type: {}
• Failed to deserialize object type
• Should be specified either value() or name() attribute in th
• Cannot use both value() and name() attribute in the @CacheNa

AI-assisted analysis of baomidou/mybatis-plus@bf67d90747 (2026-08-14). Data as JSON: /api/errors/4b7d472aaacb07cc. Report an issue: GitHub.