与 string.getBytes() 混淆

Question

我有一个由 BSON 序列化的字节数组 byteObj。

String strObj = new String(byteObj)
System.out.println(byteObj.length)
System.out.println(strObj.getBytes().length)

结果是152 和154。而且这两个字节数组是不一样的。如何从字符串中恢复原始的 bson 字节数组？

更新：

152 154
[-104, 0, 0, 0, 4, 116, 105, 116, 108, 101, 0, 80, 0, 0, 0, 2, 48, 0, 5, 0, 0, 0, 116, 104, 105, 115, 0, 2, 49, 0, 3, 0, 0, 0, 105, 115, 0, 2, 50, 0, 2, 0, 0, 0, 97, 0, 2, 51, 0, 5, 0, 0, 0, 116, 104, 105, 115, 0, 2, 52, 0, 2, 0, 0, 0, 97, 0, 2, 53, 0, 3, 0, 0, 0, 105, 115, 0, 2, 54, 0, 6, 0, 0, 0, 116, 105, 116, 108, 101, 0, 0, 4, 99, 111, 110, 116, 101, 110, 116, 0, 51, 0, 0, 0, 2, 48, 0, 5, 0, 0, 0, 116, 104, 105, 115, 0, 2, 49, 0, 2, 0, 0, 0, 97, 0, 2, 50, 0, 8, 0, 0, 0, 99, 111, 110, 116, 101, 110, 116, 0, 2, 51, 0, 3, 0, 0, 0, 105, 115, 0, 0, 0]
[-17, -65, -67, 0, 0, 0, 4, 116, 105, 116, 108, 101, 0, 80, 0, 0, 0, 2, 48, 0, 5, 0, 0, 0, 116, 104, 105, 115, 0, 2, 49, 0, 3, 0, 0, 0, 105, 115, 0, 2, 50, 0, 2, 0, 0, 0, 97, 0, 2, 51, 0, 5, 0, 0, 0, 116, 104, 105, 115, 0, 2, 52, 0, 2, 0, 0, 0, 97, 0, 2, 53, 0, 3, 0, 0, 0, 105, 115, 0, 2, 54, 0, 6, 0, 0, 0, 116, 105, 116, 108, 101, 0, 0, 4, 99, 111, 110, 116, 101, 110, 116, 0, 51, 0, 0, 0, 2, 48, 0, 5, 0, 0, 0, 116, 104, 105, 115, 0, 2, 49, 0, 2, 0, 0, 0, 97, 0, 2, 50, 0, 8, 0, 0, 0, 99, 111, 110, 116, 101, 110, 116, 0, 2, 51, 0, 3, 0, 0, 0, 105, 115, 0, 0, 0]

首先是 BSON 字节数组。

更新 2： 测试代码

    BSONObject ob = new BasicBSONObject()
            .append("title", Arrays.asList(new String[]{"this", "is", "a", "this", "a", "is", "title"}))
            .append("content", Arrays.asList(new String[]{"this", "a", "content", "is"}));


    byte[] ahaha = BSON.encode(ob);
    BSON.decode(ahaha);

    // BSON.decode(new String(ahaha).getBytes());

    byte[] strByte = new String(ahaha).getBytes();

    System.out.println(ahaha.length + "\t" + strByte.length);
    System.out.println(Arrays.toString(ahaha));
    System.out.println(Arrays.toString(strByte));

二进制数据转换为字符串，反之亦然的解决方案见How do you convert binary data to Strings and back in Java?。

Answer 1

差异的原因是字节到字符串的转换。请注意，第一个字节是负数。这是Javadoc的解释：

新字符串的长度是字符集的函数，因此可能不等于字节数组的长度。 当给定字节在默认字符集中无效时，此构造函数的行为未指定。

当需要对解码过程进行更多控制时，应使用 CharsetDecoder 类。

Answer 2

我无法重现该问题。以下代码返回相同的长度（152）并且字节相同：

byte[] bs = {-104, 0, 0, 0, 4, 116, 105, 116, 108, 101, 0, 80, 0, 0, 0, 2, 48, 0, 5, 0, 0, 0, 116, 104, 105, 115, 0, 2, 49, 0, 3, 0, 0, 0, 105, 115, 0, 2, 50, 0, 2, 0, 0, 0, 97, 0, 2, 51, 0, 5, 0, 0, 0, 116, 104, 105, 115, 0, 2, 52, 0, 2, 0, 0, 0, 97, 0, 2, 53, 0, 3, 0, 0, 0, 105, 115, 0, 2, 54, 0, 6, 0, 0, 0, 116, 105, 116, 108, 101, 0, 0, 4, 99, 111, 110, 116, 101, 110, 116, 0, 51, 0, 0, 0, 2, 48, 0, 5, 0, 0, 0, 116, 104, 105, 115, 0, 2, 49, 0, 2, 0, 0, 0, 97, 0, 2, 50, 0, 8, 0, 0, 0, 99, 111, 110, 116, 101, 110, 116, 0, 2, 51, 0, 3, 0, 0, 0, 105, 115, 0, 0, 0};

System.out.println(new String(bs).getBytes().length);
System.out.println(bs.length);