I am trying to convert a json api to excel table. I tried different parsing methods but currently using VBA-JSON (similar to VB-JSON but faster parsing). So far I got it to convert into a Object. It is a collection if I'm correct. However to convert the object into a table costs a huge amount of time.
The following is my code. On this old machine I'm using, the HTTP > string uses 9s. Parsing into the object costs 14s. These are acceptable but the for loop to go through one column (25k rows) in the collection costs 30+s. I need around 8 columns to get from the collection and that would take way too long. And it takes just as long in my i5 machine.
Dim ItemCount As Integer
Dim itemID() As Long
Function httpresp(URL As String) As String
Dim x As Object: Set x = CreateObject("MSXML2.XMLHTTP")
x.Open "GET", URL, False
x.send
httpresp = x.responseText
End Function
Private Sub btnLoad_Click()
Application.Calculation = xlCalculationManual
Application.ScreenUpdating = false
Dim URL As String: URL = "https://www.gw2shinies.com/api/json/item/tp"
Dim DecJSON As Object: Set DecJSON = JsonConverter.ParseJson(httpresp(URL))
ItemCount = DecJSON.Count
ReDim itemID(1 To ItemCount)
Range("A2:S25000").Clear 'clear range
For i = 1 To ItemCount
Cells(i + 1, 1).Value = DecJSON(i)("item_id")
Next i
Application.ScreenUpdating = True
Application.Calculation = xlCalculationAutomatic
End Sub
Is there anyway I can populate the excel table faster from the huge collection object?
I also checked Rest to Excel library but I fail to understand it after studying for hours......plus I don't know even if I get it to work, how would it perform.
Consider the below example, there is pure VBA JSON parser. It's quite fast, but not so flexible, so it's suitable for parsing of simple json array of objects containing table-like data only.
Option Explicit
Sub Test()
Dim strJsonString As String
Dim arrResult() As Variant
' download
strJsonString = DownloadJson("https://www.gw2shinies.com/api/json/item/tp")
' process
arrResult = ConvertJsonToArray(strJsonString)
' output
Output Sheets(1), arrResult
End Sub
Function DownloadJson(strUrl As String) As String
With CreateObject("MSXML2.XMLHTTP")
.Open "GET", strUrl
.Send
If .Status <> 200 Then
Debug.Print .Status
Exit Function
End If
DownloadJson = .responseText
End With
End Function
Function ConvertJsonToArray(strJsonString As String) As Variant
Dim strCnt As String
Dim strMarkerQuot As String
Dim arrUnicode() As String
Dim arrQuots() As String
Dim arrRows() As String
Dim arrProps() As String
Dim arrTokens() As String
Dim arrHeader() As String
Dim arrColumns() As Variant
Dim arrColumn() As Variant
Dim arrTable() As Variant
Dim j As Long
Dim i As Long
Dim lngMaxRowIdx As Long
Dim lngMaxColIdx As Long
Dim lngPrevIdx As Long
Dim lngFoundIdx As Long
Dim arrProperty() As String
Dim strPropName As String
Dim strPropValue As String
strCnt = Split(strJsonString, "[{")(1)
strCnt = Split(strCnt, "}]")(0)
strMarkerQuot = Mid(CreateObject("Scriptlet.TypeLib").GUID, 2, 36)
strCnt = Replace(strCnt, "\\", "\")
strCnt = Replace(strCnt, "\""", strMarkerQuot)
strCnt = Replace(strCnt, "\/", "/")
strCnt = Replace(strCnt, "\b", Chr(8))
strCnt = Replace(strCnt, "\f", Chr(12))
strCnt = Replace(strCnt, "\n", vbLf)
strCnt = Replace(strCnt, "\r", vbCr)
strCnt = Replace(strCnt, "\t", vbTab)
arrUnicode = Split(strCnt, "\u")
For i = 1 To UBound(arrUnicode)
arrUnicode(i) = ChrW(CLng("&H" & Left(arrUnicode(i), 4))) & Mid(arrUnicode(i), 5)
Next
strCnt = Join(arrUnicode, "")
arrQuots = Split(strCnt, """")
ReDim arrTokens(UBound(arrQuots) \ 2)
For i = 1 To UBound(arrQuots) Step 2
arrTokens(i \ 2) = Replace(arrQuots(i), strMarkerQuot, """")
arrQuots(i) = "%" & i \ 2
Next
strCnt = Join(arrQuots, "")
strCnt = Replace(strCnt, " ", "")
arrRows = Split(strCnt, "},{")
lngMaxRowIdx = UBound(arrRows)
For j = 0 To lngMaxRowIdx
lngPrevIdx = -1
arrProps = Split(arrRows(j), ",")
For i = 0 To UBound(arrProps)
arrProperty = Split(arrProps(i), ":")
strPropName = arrProperty(0)
If Left(strPropName, 1) = "%" Then strPropName = arrTokens(Mid(strPropName, 2))
lngFoundIdx = GetArrayItemIndex(arrHeader, strPropName)
If lngFoundIdx = -1 Then
ReDim arrColumn(lngMaxRowIdx)
If lngPrevIdx = -1 Then
ArrayAddItem arrHeader, strPropName
lngPrevIdx = UBound(arrHeader)
ArrayAddItem arrColumns, arrColumn
Else
lngPrevIdx = lngPrevIdx + 1
ArrayInsertItem arrHeader, lngPrevIdx, strPropName
ArrayInsertItem arrColumns, lngPrevIdx, arrColumn
End If
Else
lngPrevIdx = lngFoundIdx
End If
strPropValue = arrProperty(1)
If Left(strPropValue, 1) = "%" Then strPropValue = arrTokens(Mid(strPropValue, 2))
arrColumns(lngPrevIdx)(j) = strPropValue
Next
Next
lngMaxColIdx = UBound(arrHeader)
ReDim arrTable(lngMaxRowIdx + 1, lngMaxColIdx)
For i = 0 To lngMaxColIdx
arrTable(0, i) = arrHeader(i)
Next
For j = 0 To lngMaxRowIdx
For i = 0 To lngMaxColIdx
arrTable(j + 1, i) = arrColumns(i)(j)
Next
Next
ConvertJsonToArray = arrTable
End Function
Sub Output(objSheet As Worksheet, arrCells() As Variant)
With objSheet
.Select
.Range(.Cells(1, 1), Cells(UBound(arrCells, 1) + 1, UBound(arrCells, 2) + 1)).Value = arrCells
.Columns.AutoFit
End With
With ActiveWindow
.SplitColumn = 0
.SplitRow = 1
.FreezePanes = True
End With
End Sub
Function GetArrayItemIndex(arrElements, varTest)
For GetArrayItemIndex = 0 To SafeUBound(arrElements)
If arrElements(GetArrayItemIndex) = varTest Then Exit Function
Next
GetArrayItemIndex = -1
End Function
Sub ArrayAddItem(arrElements, varElement)
ReDim Preserve arrElements(SafeUBound(arrElements) + 1)
arrElements(UBound(arrElements)) = varElement
End Sub
Sub ArrayInsertItem(arrElements, lngIndex, varElement)
Dim i As Long
ReDim Preserve arrElements(SafeUBound(arrElements) + 1)
For i = UBound(arrElements) To lngIndex + 1 Step -1
arrElements(i) = arrElements(i - 1)
Next
arrElements(i) = varElement
End Sub
Function SafeUBound(arrTest)
On Error Resume Next
SafeUBound = -1
SafeUBound = UBound(arrTest)
End Function
It takes about 5 secs for downolad (approx. 7 MB), 10 secs for processing and 1.5 for output for me. The resulting worksheet contains 23694 rows including table header:
Update
Fast jsJsonParser may help to process large amount of data. Check this Douglas Crockford json2.js implementation for VBA
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