B4J Code Snippet May Be JSON (MayBeJSON)

B4X implementation of the "mayBeJSON" method from JSON Lib - https://github.com/jenkinsci/json-lib

The method tests if the input String possibly represents a valid JSON String. This is handy as a check before running the JSONParser.

Sub MayBeJSON(Input As String) As Boolean
    If Input.Length = 0 Then Return False
    If Input = Null Then Return False
    If Input.ToLowerCase = "null" Then Return False
    If Input.StartsWith("{") And Input.EndsWith("}") Then Return True
    If Input.StartsWith("[") And Input.EndsWith("]") Then Return True   
    Return False   
End Sub

 

[peacemaker]

#if B4R
Sub MayBeJSON (Input() As Byte) As Boolean
    Dim bc As ByteConverter
    If Input.Length = 0 Then
        Return False
    End If
    If bc.StartsWith(Input, "{".GetBytes) And bc.EndsWith(Input, "}".GetBytes) Then Return True
    If bc.StartsWith(Input, "[".GetBytes) And bc.EndsWith(Input, "]".GetBytes) Then Return True
    Return False
End Sub
#Else
Sub MayBeJSON(Input As String) As Boolean
    If Input.Length = 0 Then Return False
    If Input = Null Then Return False
    If Input.ToLowerCase = "null" Then Return False
    If Input.StartsWith("{") And Input.EndsWith("}") Then Return True
    If Input.StartsWith("[") And Input.EndsWith("]") Then Return True
    Return False
End Sub
#end if

 

[stevel05]

I had this problem recently and decided on the brute force approach. Put the parser in a try ... catch block. If it succeeds, then it's valid otherwise not. I'm sure there are still some situations that will slip through.

 

[peacemaker]

Note i'm updating for B4R...
Where MCU also can hang, and no another "try" to re-try