與string.getBytes混淆（）

Question

我有一個字節數組byteObj它由BSON序列化。

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

結果是152和154。而這兩個字節數組並不相同。如何從字符串中恢復原始的bson字節數組？

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字節數組。

更新2： 測試代碼

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)); 

二進制數據轉換爲字符串，並且反之亦然的溶液見How do you convert binary data to Strings and back in Java?。

Answer 1

區別的原因是將字節轉換爲字符串。請注意，第一個字節是負數。這裏是從Javadoc的解釋：

新字符串的長度是字符集的函數，因此可能不等於字節數組的長度。 未指定給定字節在默認字符集中無效時此構造函數的行爲。

當需要對解碼過程進行更多的控制時，應該使用CharsetDecoder類。

Answer 2

我無法重現該問題。下面的代碼返回相同的長度（152）和字節是相同的：

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);