YunaiV/ruoyi-vue-pro · error · IllegalArgumentException

数据长度 超过固定长度

Error message

数据长度 %d 超过固定长度 %d

What it means

encode() throws IllegalArgumentException when the outbound data byte length exceeds the configured fixedLength. The fixed-length codec zero-pads shorter payloads but cannot truncate longer ones, so an oversized payload is a hard error. This is an encode-side (downstream/command) failure, not a decode failure.

Solutions

1. Increase fixedLength to fit the largest legitimate payload (and align with the device's expected frame size).
2. If payloads vary, switch from FIXED_LENGTH to LENGTH_FIELD or DELIMITER codec which handle variable sizes.
3. Validate data.length <= fixedLength before calling encode() and fail the command with a clear business error.

Example fix

// before: encode throws when payload exceeds fixedLength
byte[] cmd = buildLargeCommand(); // longer than fixedLength
Buffer out = codec.encode(cmd);

// after: validate up front and use a variable-length codec
if (cmd.length > fixedLength) {
    throw new IllegalArgumentException("command too large for fixed frame");
}

// before encoding, validate payload fits the fixed frame
if (data.length > fixedLength) {
    throw new IllegalArgumentException(
        String.format("数据长度 %d 超过固定长度 %d", data.length, fixedLength));
}
// or, at config time, ensure fixedLength >= max command payload size

boolean fitsFixedFrame(byte[] data, int fixedLength) {
    return data != null && data.length <= fixedLength;
}

When it happens

Trigger: Calling encode(byte[]) with a payload longer than fixedLength; a downstream command whose serialized body grew beyond the agreed frame size; fixedLength misconfigured smaller than the protocol's largest message.

Common situations: Command payload size increased after a firmware/protocol change; fixedLength set to a value too small; developer assumed encode would truncate.

Related errors

• [createDecodeParser][消息体不能为空]
• [createDecodeParser][解析异常]
• [createDecodeParser]
• [createDecodeParser][解析异常]
• [createDecodeParser][解析异常]

AI-assisted analysis of YunaiV/ruoyi-vue-pro@0418084e22 (2026-08-14). Data as JSON: /api/errors/9b62708f23de61d5. Report an issue: GitHub.

Appendix: source

Thrown at yudao-module-iot/yudao-module-iot-gateway/src/main/java/cn/iocoder/yudao/module/iot/gateway/protocol/tcp/codec/length/IotTcpFixedLengthFrameCodec.java:51

    public IotTcpCodecTypeEnum getType() {
        return IotTcpCodecTypeEnum.FIXED_LENGTH;
    }

    @Override
    public RecordParser createDecodeParser(Handler<Buffer> handler) {
        RecordParser parser = RecordParser.newFixed(fixedLength);
        parser.handler(handler);
        parser.exceptionHandler(ex -> {
            throw new RuntimeException("[createDecodeParser][解析异常]", ex);
        });
        return parser;
    }

    @Override
    public Buffer encode(byte[] data) {
        // 校验数据长度不能超过固定长度
        if (data.length > fixedLength) {
            throw new IllegalArgumentException(String.format(
                    "数据长度 %d 超过固定长度 %d", data.length, fixedLength));
        }
        Buffer buffer = Buffer.buffer(fixedLength);
        buffer.appendBytes(data);
        // 如果数据不足固定长度，填充 0（RecordParser.newFixed 解码时按固定长度读取，所以发送端需要填充）
        if (data.length < fixedLength) {
            byte[] padding = new byte[fixedLength - data.length];
            buffer.appendBytes(padding);
        }
        return buffer;
    }

}

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