解码将bytebuffer转换为在java中不起作用的字符串

Question

在运行时，我从设备获取字节缓冲数据，我试图解码该数据以读取其内容

当我使用字符串打印bytebuffer时，它显示如下：

java.nio.HeapByteBuffer[pos=0 lim=3 cap=3]

我试着用所有已知的格式解码如下

       CharBuffer charBuffer = StandardCharsets.UTF_8.decode(paramByteBuffer);
       String text = charBuffer.toString();
       System.out.println("UTF-8"+text); 
       charBuffer = StandardCharsets.UTF_16.decode(paramByteBuffer);
       text = charBuffer.toString();
       System.out.println("UTF_16"+text); 
       charBuffer = StandardCharsets.ISO_8859_1.decode(paramByteBuffer);
       text = charBuffer.toString();
       System.out.println("ISO_8859_1"+text); 
       charBuffer = StandardCharsets.UTF_16BE.decode(paramByteBuffer);
       text = charBuffer.toString();
       System.out.println("UTF_16BE"+text); 
       charBuffer = StandardCharsets.UTF_16LE.decode(paramByteBuffer);
       text = charBuffer.toString();
       System.out.println("UTF_16LE"+text); 
       charBuffer = StandardCharsets.US_ASCII.decode(paramByteBuffer);
       text = charBuffer.toString();
       System.out.println("US_ASCII"+text); 

一切都返回空数据

解码字节缓冲区数据的方法是什么

Answer 1

缓冲区使用起来有点棘手，因为它们有一个当前状态，在访问它们时需要考虑这个状态

你想把

 paramByteBuffer.flip();

在每次解码之前，将缓冲区置于您希望解码读取的状态

例如

ByteBuffer paramByteBuffer = ByteBuffer.allocate(100);
paramByteBuffer.put((byte)'a');  // write 'a' at next position(0)
paramByteBuffer.put((byte)'b');  // write 'b' at next position(1)
paramByteBuffer.put((byte)'c');  // write 'c' at next position(2)

// if I try to read now I will read the next byte position(3) which is empty
// so I need to flip the buffer so the next position is at the start
paramByteBuffer.flip();          

// we are at position 0 so we can do our read function
CharBuffer charBuffer = StandardCharsets.UTF_8.decode(paramByteBuffer);
String text = charBuffer.toString();
System.out.println("UTF-8" + text);

// because the decoder has read all the written bytes we are back to the
// state (position 3) we had just after we wrote the bytes in the first 
// place so we need to flip again 
paramByteBuffer.flip();

// we are now at position 0 so we can do our read function
charBuffer = StandardCharsets.UTF_16.decode(paramByteBuffer);
text = charBuffer.toString();
System.out.println("UTF_16"+text);

Answer 2

HeapByteBuffer的^{}方法很简单

Returns a string summarizing the state of this buffer.

换句话说，它会回来

java.nio.HeapByteBuffer[pos=0 lim=3 cap=3]

显示字节缓冲区的位置、限制和容量

在这种情况下，您的ByteBuffer还有3个字节的容量。每个Charset#decode调用都会使用ByteBuffer而您不需要rewind/reset它，因此后续调用没有更多的字节可使用。换句话说，所有这些字符串都将为空

Answer 3

您可以这样做：

String val = new String(paramByteBuffer.array());

或

String val = new String(paramByteBuffer.array(),"UTF-8");

Here是受支持的字符集列表