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 将这些字节比较为 long.我希望将 long 的值转换为对 Cassandra 友好的 byte[].如何?我摸索了一会儿.我认为你们可以更快地帮助我.

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.

Alexander 和 Eli 的回答都同意 此逆向转换.谢谢！

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

推荐答案

这里是从 java 6 剪切粘贴过来的 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);
}

这里是针对您的情况的修改

Here are modifications for your case

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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