ios resolves a data request JSON parsing dictionary, because some Java class libraries convert JSON strings after the key value of <null> cannot be saved in the Userdefault problem

After resolving the data request JSON parsing dictionary, a key value of <null> cannot be saved in Userdefault because some Java class libraries convert the JSON string.

To print the resulting dictionary data:

"Username" =<null>

If you save the dictionary to Userdefault, an error will be displayed.

So you need to traverse the dictionary to replace it

for (nsstring*s in [Dict1 AllKeys]) {            if ([dict1[s] isequal:[nsnull null]) {                [Dict1 setobject:@] "forkey:s];
  
   }        }        [Dict2 Addentriesfromdictionary:dict1];
  

<null> is expressed in OC, and for a long time, it is equivalent to [NSNull NULL]

ios resolves a data request JSON parsing dictionary, because some Java class libraries convert JSON strings after the key value of <null> cannot be saved in the Userdefault problem