如何将Java Long转换为Cassandra的byte []？ [英] How to convert a Java Long to byte[] for Cassandra?

问题描述

懒惰的程序员警报。 ：）

Lazy programmer alert. :)

Cassandra将列值存储为字节（ Java示例）。指定 LongType比较器会将这些字节作为长整型。我想要一个长的值到Cassandra友好的字节[]。怎么样？我戳了一会儿。我认为你的人可以帮助我更快。

Cassandra stores column values as bytes (Java example). Specifying a LongType comparator compares those bytes as a long. I want the value of a long into a Cassandra-friendly byte[]. How? I poked around for awhile. I think you people can help me faster.

编辑：

Eli的回答符合这个反向变换。谢谢！

Both Alexander and Eli's answers agreed with this reverse transformation. Thanks!

推荐答案

这里是从Java 6剪切和粘贴 DataOutputStream.writeLong

Here is cut and paste from java 6 DataOutputStream.writeLong

public final void writeLong(long v) throws IOException {
    writeBuffer[0] = (byte)(v >>> 56);
    writeBuffer[1] = (byte)(v >>> 48);
    writeBuffer[2] = (byte)(v >>> 40);
    writeBuffer[3] = (byte)(v >>> 32);
    writeBuffer[4] = (byte)(v >>> 24);
    writeBuffer[5] = (byte)(v >>> 16);
    writeBuffer[6] = (byte)(v >>>  8);
    writeBuffer[7] = (byte)(v >>>  0);
    out.write(writeBuffer, 0, 8);
incCount(8);
}

这里是您的情况的修改

public final byte[] longToBytes(long v) {
    byte[] writeBuffer = new byte[ 8 ];

    writeBuffer[0] = (byte)(v >>> 56);
    writeBuffer[1] = (byte)(v >>> 48);
    writeBuffer[2] = (byte)(v >>> 40);
    writeBuffer[3] = (byte)(v >>> 32);
    writeBuffer[4] = (byte)(v >>> 24);
    writeBuffer[5] = (byte)(v >>> 16);
    writeBuffer[6] = (byte)(v >>>  8);
    writeBuffer[7] = (byte)(v >>>  0);

    return writeBuffer;
}

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