字节数组的java GUID

Question

我写这段代码是为了将GUID转换成字节数组。有人能在上面打洞或提出更好的建议吗

 public static byte[] getGuidAsByteArray(){

 UUID uuid = UUID.randomUUID();
 long longOne = uuid.getMostSignificantBits();
 long longTwo = uuid.getLeastSignificantBits();

 return new byte[] {
      (byte)(longOne >>> 56),
      (byte)(longOne >>> 48),
      (byte)(longOne >>> 40),
      (byte)(longOne >>> 32),   
      (byte)(longOne >>> 24),
      (byte)(longOne >>> 16),
      (byte)(longOne >>> 8),
      (byte) longOne,
      (byte)(longTwo >>> 56),
      (byte)(longTwo >>> 48),
      (byte)(longTwo >>> 40),
      (byte)(longTwo >>> 32),   
      (byte)(longTwo >>> 24),
      (byte)(longTwo >>> 16),
      (byte)(longTwo >>> 8),
      (byte) longTwo
       };
}

在C++中，我记得能够做到这一点，但是我想在java中没有办法用内存管理和所有的方法来做：

    UUID uuid = UUID.randomUUID();

    long[] longArray = new long[2];
    longArray[0] = uuid.getMostSignificantBits();
    longArray[1] = uuid.getLeastSignificantBits();

    byte[] byteArray = (byte[])longArray;
    return byteArray;

编辑

如果您想将完全随机的UUID生成为不符合任何正式类型的字节，这将比UUID生成的类型4 UUID更有效，并且浪费10 fewer bits。randomUUID（）：

    public static byte[] getUuidAsBytes(){
    int size = 16;
    byte[] bytes = new byte[size];
    new Random().nextBytes(bytes);
    return bytes;
}

Answer 1

您可以看看ApacheCommonsLang3Conversion.uuidToByteArray(...)。相反，请查看Conversion.byteArrayToUuid(...)以将其转换回UUID

Answer 2

public static byte[] newUUID() {
    UUID uuid = UUID.randomUUID();
    long hi = uuid.getMostSignificantBits();
    long lo = uuid.getLeastSignificantBits();
    return ByteBuffer.allocate(16).putLong(hi).putLong(lo).array();
}

Answer 3

我将依赖于内置功能：

ByteBuffer bb = ByteBuffer.wrap(new byte[16]);
bb.putLong(uuid.getMostSignificantBits());
bb.putLong(uuid.getLeastSignificantBits());
return bb.array();

或者类似的

ByteArrayOutputStream ba = new ByteArrayOutputStream(16);
DataOutputStream da = new DataOutputStream(ba);
da.writeLong(uuid.getMostSignificantBits());
da.writeLong(uuid.getLeastSignificantBits());
return ba.toByteArray();

（注意，未测试的代码！）

Answer 4

您可以从apache commons中检查^{}。您可能不想使用它，但请检查sources以了解其getRawBytes()方法是如何实现的：

public UUID(long mostSignificant, long leastSignificant) {
    rawBytes = Bytes.append(Bytes.toBytes(mostSignificant), Bytes.toBytes(leastSignificant));
}