B4J Code Snippet [B4x]: Better JSON handling of Lists with Maps without parsing errors

I've seen some threads about problems parsing JSON strings (esp. lists/maps) due to special chars (e.g. when a value contains a Base64 string). I now had one app which sends JSON strings (a list with n maps) via network. In some cases I had problems parsing the strings due to "invalid chars or delimiters).

The reason was that I've added maps directly to a list and then converted the list to a JSON string. Somehow this doesn't work when you send the data via network (AsyncStreams or Http) when you don't url encode the data.



B4X:
    Dim l As List
    l.Initialize
    Dim m1 As Map = CreateMap("key":"value")
    Dim m2 As Map = CreateMap("key":"value")
    
    
'adding maps to the list
    l.Add(m1) 'add the map to the list
    l.Add(m2)
    JG.Initialize2(l)
    Dim JSONString As String = JG.ToString
    Log(JSONString)

Output: [{"key":"value"},{"key":"value"}] -> problematic

To solve this issue I convert the maps to a JSON string BEFORE I add them to the list. This seems to escape chars which can interfere.

B4X:
'Better: Adding maps which were converted to JSON-Strings before
    l.Clear
    JG.Initialize(m1)
    l.Add(JG.ToString)
    JG.Initialize(m2)
    l.Add(JG.ToString)
    JG.Initialize2(l)
    JSONString=JG.ToString
    Log(JSONString)

Output: ["{\"key\":\"value\"}","{\"key\":\"value\"}"] -> good
 

AnandGupta

Well-Known Member
Licensed User
Yes, I am also curious as the second json is invalid as per Json Validator.

Regards,

Anand
 
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