如何从Java中的字节数组中获取数据？

Posted 2023-02-24

【中文标题】如何从Java中的字节数组中获取数据？

【英文标题】：How to get the data from the byte array in Java?

【发布时间】：2015-02-05 09:30:42

【问题描述】：

我使用byte[512] 从 Java 中的套接字接收数据

我使用函数bytesToHexString让它可见

public static String bytesToHexString(byte[] src) 
    StringBuilder stringBuilder = new StringBuilder("");
    if (src == null || src.length <= 0) 
        return null;
    
    for (int i = 0; i < src.length; i++) 
        int v = src[i] & 0xFF;
        String hv = Integer.toHexString(v);
        if (hv.length() < 2) 
            stringBuilder.append(0);
        
        stringBuilder.append(hv + " ");
    
    return stringBuilder.toString();

它看起来像这样：

50 1c 04 80 00 00 ce 01 4d 6f 64 69 6d 20 66 61 73 68 69 6f 6e 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 64 33 36 30 57 69 46 69 2d 36 38 38 38 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 5a 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 50 74 69 6d 65 6c 65 73 73 67 7a 32 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 4b 77 7a 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 43 74 69 6d 65 6c 65 73 73 67 7a 31 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 39 72 69 6e 67 69 65 72 67 75 65 73 74 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 39 73 77 65 65 74 20 62 61 62 79 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 34 4a 49 4d 4d 59 20 33 47 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 28 42 65 72 74 2d 43 6f 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 28 54 50 2d 4c 49 4e 4b 5f 43 42 44 30 34 43 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 25 43 68 69 6e 61 4e 65 74 2d 47 50 69 36 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 23 43 68 69 6e 61 4e 65 74 2d 55 6c 36 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 11 62 6c 75 65 31 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 11 95 bd 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 

而我所知道的是 C 中的这个结构：

typedef struct _xchip_cmd_head 
  u16 flag; //always 50 1c
  u16 cmd; // commands, return cmd=cmd|0x8000
  u16 cmd_status; //return result
  u16 datalen; 
  u8 data[1]; 
xchip_cmd_head_t;

50 1c 是开始标志

04 80 是命令

00 00 是一种状态

ce 01是数据的长度。

之后ce 01

是ssid的列表：

typedef  struct  _ApList_str  
  
  char ssid[32];  
  char ApPower;  // min:0, max:100
ApList_str; 

那么如何在 Java 中获取 ssid 列表呢？

我做了一些搜索，有没有办法使用ByteBuffer？

【问题讨论】：

有点不清楚你想要什么：你已经在Java端成功解析了字节数组，甚至将内容打印为十六进制字符串，你没有做些什么？

@gio 我想要做的是拆分 ssid 的字符串，并将其放入 List

【参考方案1】：

50 1c 是开始标志

04 80 是命令

00 00 是一种状态

ce 01 是 ssid 列表长度

如果上面的列表是常量，类似于应用程序协议缓冲区，那么您可以解析字节数组并打印值。 检查半径数据包的解析。

【讨论】：

那么如何解析呢？如何将此十六进制值转换为字符串？

可以通过此链接mdsaputra.wordpress.com/2010/09/03/… 将十六进制值转换为字符串，反之亦然

【参考方案2】：

你没有说ApPower在哪里编码，否则这个类会做你想做的。

public class ApList_str 

    private final String ssid;
    private int ApPower = -1; /* Unknown */

    public ApList_str(String ssid) 

        this.ssid = ssid;
    

    public String getSsid() 
        return ssid;
    

    public int getApPower() 
        return ApPower;
    

    public void setApPower(int apPower) 
        ApPower = apPower;
    

    public static ApList_str fromBytes(ByteBuffer b) throws UnsupportedEncodingException 

        byte[] ssid_bytes = new byte[32];
        b.get(ssid_bytes);

        /* You should change the encoding depending on your situation */
        return new ApList_str(new String(ssid_bytes, "UTF-8"));
    

【讨论】：

嗨，但我还不知道如何使用这个类。我得到的是一个byte[512] 以及如何拆分这个字节数组？？？

你可以使用 ByteBuffer.wrap() 吗？

【参考方案3】：

最后我通过这个函数获得了ssid 列表。它看起来很愚蠢，但它确实有效。

我想找到更好的方法：

public static List<String> getSsidList(byte[] byteRecv) 
    System.out.println("get from device");
    List<String> ssidListOpt = new ArrayList<String>();

    try 
        if (byteRecv[0] != 0) 
            // make it visabled
            String test = BytesUtil.bytesToHexString(byteRecv);
            // replace the space
            test = test.replace(" ", "");
            // get rid of the head data
            test = test.substring(16);
            String temp = "";

            // split the ssid,add "," between every ssid item
            for (int i = 0; i < test.length(); i++) 
                if (i % 66 == 0 && i != 0) 
                    temp += ",";
                
                temp += test.substring(i, i + 1);
            
            // put it into the string array
            String temps[] = temp.split(",");

            for (int i = 0; i < temps.length; i++) 

                if (temps[i].endsWith("00")) 
                    continue;
                

                int l = temps[i].length();
                // get the hex ssid name
                String ssidName = temps[i].substring(0, l - 2);
                // delete all of 0x00 at the end
                ssidName = BytesUtil.deleteLastZero(ssidName);
                // hex ssid name to string
                ssidName = BytesUtil.toStringHex(ssidName);

                if ("".equals(ssidName)) 
                    continue;
                

                // get the hex ApPower
                String signal = temps[i].substring(l - 2, l);
                // hex to int
                signal = Integer.parseInt(signal, 16) + "";
                String t[] = ssidName, signal;
                System.out.println("" + t[0] + "------" + t[1]);

                ssidListOpt.add(ssidName);
            
        
     catch (Exception e) 
        e.printStackTrace();
    
    return ssidListOpt;

这就是我在 LogCat 中得到的：

02-06 15:06:40.398: I/System.out(20947): Modim fashion------100
02-06 15:06:40.398: I/System.out(20947): tessgz2------80
02-06 15:06:40.398: I/System.out(20947): sweet baby------67
02-06 15:06:40.398: I/System.out(20947): wz------62
02-06 15:06:40.408: I/System.out(20947): Bert-Co------45
02-06 15:06:40.408: I/System.out(20947): ChinaNet-GPi6------40
02-06 15:06:40.408: I/System.out(20947): ringierguest------40
02-06 15:06:40.408: I/System.out(20947): tlessgz1------32
02-06 15:06:40.408: I/System.out(20947): JIMMY 3G------32
02-06 15:06:40.408: I/System.out(20947): blue1------30
02-06 15:06:40.408: I/System.out(20947): ChinaNet-Ul6------25
02-06 15:06:40.408: I/System.out(20947): wudiuandiuan------15