从JSON中提取字节数组 [英] Extracting a byte array from a JSON

问题描述

我有以下格式的JSON：

  [{fingerprint：[79,0,0， 0,18,0,0,0,18,0,0,0,19,0,0,0,23,0,0,0,40,0,0,0,42,0,0,0， 63,0,0,0,68,0,0,0,71,0，....]}] 
  

我一直试图从它中提取字节数组，使用以下代码：

  JSONFingerprint fingerprintData = gson .fromJson（obj，JSONFingerprint.class）; 
  

其中JSONFingerprint是：

  public class JSONFingerprint {
 
 byte []指纹; 
 
 public byte [] getfingerprintData（）{
返回指纹; 
} 
 
} 
  

我得到这个错误：

 线程Thread-0中的异常com.google.gson.JsonSyntaxException：java.lang.IllegalStateException：预期的BEGIN_ARRAY，但是STRING 
 at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory $ Adapter.read（ReflectiveTypeAdapterFactory.java:176）
 at com.google.gson.Gson.fromJson（Gson.java:795）
在com.google.gson.Gson.fromJson（Gson.java:859）
在com.google.gson.Gson.fromJson（Gson.java:832）
  

有人有什么想法吗？

解决方案

看起来您的 JSON 和 POJO 不匹配。可能有两种可能的解决方案。

解决方案1： -

如果你不能改变JSON格式（即）你的JSON就是这样，

  [{fingerprint：[79 ，0,0,0,18,0,0,0,18,0,0,0,19,0,0,0,23,0,0,0,40,0,0,0,42,0 ，0,0,63,0,0,0,68,0,0,0,71,0，....]}] 
  

然后，您需要将 JSONFingerprint 类更改为： -

  public class JSONFingerprint {
 
字符串指纹; 
 
 public String getfingerprintData（）{
 return fingerprint; 
 
 
 $ / code $ / pre 
 
 
你需要解析 JSON 像这样： -  
  JSONFingerprint [] dummy = new JSONFingerprint [0]; 
 JSONFingerprint [] fingerPrint = gson.fromJson（json，dummy.getClass（））; 
 System.out.println（fingerPrint [0] .getfingerprintData（））; 
  
 解决方案2：  
 
 
如果你的POJO不能改变（即）你的POJO就是这样， 
 
 
  public class JSONFingerprint {
 
 byte []指纹; 
 
 public byte [] getfingerprintData（）{
返回指纹; 
 
 
 
 
 $ b $ p $然后你必须改变你的<$ c 
 
 $ p $ {code> {fingerprint：[1， 2,3,4,5,6,7,8,9,10]} 
  
你可以像通常那样解析它： -  $ / $> 
 
 
  JSONFingerprint fingerprintData = gson.fromJson（obj，JSONFingerprint.class） ; 
  
希望这可以帮到你！
 
I have a JSON of the following format:
[{"fingerprint":"[79,0,0,0,18,0,0,0,18,0,0,0,19,0,0,0,23,0,0,0,40,0,0,0,42,0,0,0,63,0,0,0,68,0,0,0,71,0,....]"}]
I have been trying to extract the byte array from it using the following:
JSONFingerprint fingerprintData = gson.fromJson(obj, JSONFingerprint.class);
Where JSONFingerprint is:
public class JSONFingerprint {

    byte[] fingerprint;

    public byte[] getfingerprintData() {
        return fingerprint;
    }

}
I have been getting this error:
Exception in thread "Thread-0" com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected BEGIN_ARRAY but was STRING
    at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:176)
    at com.google.gson.Gson.fromJson(Gson.java:795)
    at com.google.gson.Gson.fromJson(Gson.java:859)
    at com.google.gson.Gson.fromJson(Gson.java:832)
Does anybody have any ideas?? 
解决方案
It seems your JSON and POJO don't match. There can be 2 possible solutions for this.

Solution 1:-

If you cannot change the JSON format(i.e.)your JSON is gonna be this,
[{"fingerprint":"[79,0,0,0,18,0,0,0,18,0,0,0,19,0,0,0,23,0,0,0,40,0,0,0,42,0,0,0,63,0,0,0,68,0,0,0,71,0,....]"}]
Then you need to change your JSONFingerprint class to this:-
public class JSONFingerprint {

    String fingerprint;

    public String getfingerprintData() {
        return fingerprint;
    }
}
and you need to parse your JSON like this:-
JSONFingerprint[] dummy = new JSONFingerprint[0]; 
JSONFingerprint[] fingerPrint = gson.fromJson(json, dummy.getClass());
System.out.println(fingerPrint[0].getfingerprintData());
Solution 2:-

If your POJO cannot change(i.e.)your POJO is gonna be this,
public class JSONFingerprint {

    byte[] fingerprint;

    public byte[] getfingerprintData() {
        return fingerprint;
    }
}
Then you'll have to change your JSON format to something like this:-
{"fingerprint":[1,2,3,4,5,6,7,8,9,10]}
which you can parse it usually, as you've already done:-
JSONFingerprint fingerprintData = gson.fromJson(obj, JSONFingerprint.class);
Hope this helps you!

                        
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