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  2. VBA cannot get data from HTML with .getElementsByTag() nor .getElementByID()

VBA cannot get data from HTML with .getElementsByTag() nor .getElementByID()

由 懵懂的女人 提交于 2019-12-25 03:29:30

问题


My current project consists of retrieving data from HTML source code. Specifically, I am looking at crash cases on this website:

https://crashviewer.nhtsa.dot.gov/nass-cds/CaseForm.aspx?xsl=main.xsl&CaseID=112007272

I would like to gather all relevant data from the HTML by looking for .innertext of specific tags/IDs.

My code so far:

Sub ExtractData()

mystart:

'First I create two Internet Explorer object

Set objIE = CreateObject("InternetExplorer.Application")      'this browser contains the list of cases
objIE.Top = 0
objIE.Left = 0
objIE.Width = 1600
objIE.Height = 900
objIE.Visible = True 'We can see IE

Set objIEdata = CreateObject("InternetExplorer.Application")    'this browser opens the specific case
objIEdata.Top = 0
objIEdata.Left = 0
objIEdata.Width = 1600
objIEdata.Height = 900
objIEdata.Visible = True 'We can see IE

On Error Resume Next
objIE.navigate ("https://crashviewer.nhtsa.dot.gov/LegacyCDS/Index")        'url of website

Do
    DoEvents
    If Err.Number <> 0 Then
        objIE.Quit
        Set objIE = Nothing
        GoTo mystart:
    End If
Loop Until objIE.readystate = 4

'we define an object variable Alllinks and loop through all the links to search for

Set aAlllinks = objIE.document.getElementsByTagName("button")                'looks for Search Button 
For Each Hyperlink In aAlllinks
    If Hyperlink.innertext = " Search" Then
        Hyperlink.Click
        Exit For
    Else
        MsgBox "Search Button was not found. Please improve code!"
    End If

Next

Application.Wait (Now + TimeValue("0:00:02"))

Set bAlllinks = objIE.document.getElementsByTagName("a")                     'all Hyperlinks on webpage start with Tag "a"
For Each Hyperlink In bAlllinks
    If UBound(Split(Hyperlink.innertext, "-")) = 2 And Len(Hyperlink.innertext) = 11 Then             'case specific to find the Hyperlinks which contain cases
        Debug.Print Hyperlink.innertext

        '2nd IE is used for each case

restart:
            objIEdata.navigate (Hyperlink.href)        'url of each case

            Do
                DoEvents
                If Err.Number <> 0 Then
                    objIEdata.Quit
                    Set objIE = Nothing
                    GoTo restart:
                End If
            Loop Until objIEdata.readystate = 4

            Set register = objIEdata.document.getElementByTagName("tbody")             'objIEdata.document.getElementByID("main").getElementByID("mainSection")  '.getElementByID("bodyMain").getElementsByTagName("tbody")
            For Each untermenue In register
                Debug.Print untermenue.innerHTML
            Next

            Application.Wait (Now + TimeValue("0:00:02"))




    End If
Next




objIE.Quit
objIEdata.Quit

End Sub

Note that the visibility of IE is just for debugging reasons.

The part which confuses me is

Set register = objIEdata.document.getElementByTagName("tbody").

If I look for .TagName("tbody") the variable register is returned empty and the same happens if I look for .ID("bodyMain"). Unfortunately, I am not familiar with HTML and how VBA interacts with a HTML document. I was under the impression that I could address all elements by their ID, if they happen to have one, but this does not seem to work.

Do I need to work myself through the HTML "branches" or should the code be able to find each ID, no matter the "child" it is to be found in?

Thanks a lot


回答1:


What you are asking is a pretty big request so I am going to give some pointers and starting code. My code should write out all the tables but you will want to play around to get your desired format. There is certainly enough logic around selecting elements efficiently that this should help. * I haven't tested the use of the class to loop over all retrieved ids due time contraints but have tested the individual case and the retrieval of all ids.

To get the initial case links and ids:

I might use a function returning an array containing the links and ids. If you extract the ids they can be passed the XMLHTTP request I show below.

URL is https://crashviewer.nhtsa.dot.gov/LegacyCDS/Search

Public Function GetLinksAndIds(ByVal URL) As Variant
    Dim ie As InternetExplorer, i As Long
    Set ie = New InternetExplorer
    With ie
        .Visible = True
        .navigate2 URL

        While .Busy Or .readyState < 4: DoEvents: Wend

        .document.getElementById("btnSubmit1").Click

         While .Busy Or .readyState < 4: DoEvents: Wend

        Dim caseLinks As Object, id As String, newURL As String
        Set caseLinks = .document.querySelectorAll("[href*='CaseID=']")

        Dim linksAndIds()
        ReDim linksAndIds(1 To caseLinks.Length, 1 To 2)
        For i = 0 To caseLinks.Length - 1
           linksAndIds(i + 1, 1) = caseLinks.item(i)
           linksAndIds(i + 1, 2) = Replace$(caseLinks.item(i), "https://crashviewer.nhtsa.dot.gov/nass-cds/CaseForm.aspx?xsl=main.xsl&CaseID=", vbNullString)
        Next

        .Quit
    End With
    GetLinksAndIds = linksAndIds
End Function

Example return values:

For each case - using XMLHTTP:

I would be tempted to avoid IE and use XMLHTTP request (url encoded query string returning more readable page version using the print option). Although I have parsed using css selectors you can read the response into an MSXML2.DOMDocument60 and query with XPath for example. You can concatenate caseid into URL. 

Option Explicit
Public Sub GetTables()
    Dim sResponse As String, html As HTMLDocument, clipboard As Object, ws As Worksheet
    Set ws = ThisWorkbook.Worksheets("Sheet1")
    Set clipboard = GetObject("New:{1C3B4210-F441-11CE-B9EA-00AA006B1A69}")

    With CreateObject("MSXML2.XMLHTTP")
        .Open "GET", "https://crashviewer.nhtsa.dot.gov/nass-cds/CaseForm.aspx?ViewPage&xsl=Case.xsl&tab=Crash&form=CaseForm&baseNode=&vehnum=-1&occnum=-1&pos=-1&pos2=-1&websrc=true&title=Crash%20Overview%20-%20Summary&caseid=112007272&year=&fullimage=false", False '<==concatenate caseid into URL
        .setRequestHeader "If-Modified-Since", "Sat, 1 Jan 2000 00:00:00 GMT"
        .send
        sResponse = .responseText
    End With

    Set html = New HTMLDocument
    html.body.innerHTML = sResponse
    Dim tables As Object, i As Long
    Set tables = html.querySelectorAll("table")
    For i = 0 To tables.Length - 1
        clipboard.SetText tables.item(i).outerHTML
        clipboard.PutInClipboard
        ws.Cells(LastRow(ws) + 2, 1).PasteSpecial
    Next
End Sub

'https://www.rondebruin.nl/win/s9/win005.htm '<< Function below modified from here

Public Function LastRow(ByVal sh As Worksheet) As Long
    On Error Resume Next
    LastRow = sh.Cells.Find(What:="*", _
                            After:=sh.Range("A1"), _
                            Lookat:=xlPart, _
                            LookIn:=xlFormulas, _
                            SearchOrder:=xlByRows, _
                            SearchDirection:=xlPrevious, _
                            MatchCase:=False).Row
    On Error GoTo 0
End Function

What might it look like altogether (not tested) using a class to hold the xmlhttp object:

Class clsHTTP:

Option Explicit

Private http As Object

Private Sub Class_Initialize()
    Set http = CreateObject("MSXML2.XMLHTTP")
End Sub

Public Function GetString(ByVal URL As String) As String
    Dim sResponse As String
    With http
        .Open "GET", URL, False
        .send
        sResponse = .responseText
    End With
End Function

Standard module 1:

Option Explicit
Public Sub GetTables()
    Dim sResponse As String, html As HTMLDocument, clipboard As Object, ws As Worksheet
    Dim initialLinksURL As String, http As clsHTTP, i As Long, j As Long, newURL As String
    Set http = New clsHTTP
    Set ws = ThisWorkbook.Worksheets("Sheet1")
    Set clipboard = GetObject("New:{1C3B4210-F441-11CE-B9EA-00AA006B1A69}")
    Set html = New HTMLDocument
    initialLinksURL = "https://crashviewer.nhtsa.dot.gov/LegacyCDS/Search"

    Dim linksAndIds()
    linksAndIds = GetLinksAndIds(initialLinksURL)

    For i = LBound(linksAndIds, 2) To UBound(linksAndIds, 2)

        newURL = "https://crashviewer.nhtsa.dot.gov/nass-cds/CaseForm.aspx?ViewPage&xsl=Case.xsl&tab=Crash&form=CaseForm&baseNode=&vehnum=-1&occnum=-1&pos=-1&pos2=-1&websrc=true&title=Crash%20Overview%20-%20Summary&caseid=" & linksAndIds(i, 2) & "&year=&fullimage=false"
        html.body.innerHTML = http.GetString(newURL)
        Dim tables As Object

        Set tables = html.querySelectorAll("table")

        For j = 0 To tables.Length - 1
            clipboard.SetText tables.item(j).outerHTML
            clipboard.PutInClipboard
            ws.Cells(LastRow(ws) + 2, 1).PasteSpecial
        Next
    Next
End Sub

'https://www.rondebruin.nl/win/s9/win005.htm

Public Function LastRow(ByVal sh As Worksheet) As Long
    On Error Resume Next
    LastRow = sh.Cells.Find(What:="*", _
                            After:=sh.Range("A1"), _
                            Lookat:=xlPart, _
                            LookIn:=xlFormulas, _
                            SearchOrder:=xlByRows, _
                            SearchDirection:=xlPrevious, _
                            MatchCase:=False).Row
    On Error GoTo 0
End Function

Public Function GetLinksAndIds(ByVal URL) As Variant
    Dim ie As InternetExplorer, i As Long
    Set ie = New InternetExplorer
    With ie
        .Visible = True
        .navigate URL

        While .Busy Or .readyState < 4: DoEvents: Wend

        .document.getElementById("btnSubmit1").Click

         While .Busy Or .readyState < 4: DoEvents: Wend

        Dim caseLinks As Object, id As String, newURL As String
        Set caseLinks = .document.querySelectorAll("[href*='CaseID=']")

        Dim linksAndIds()
        ReDim linksAndIds(1 To caseLinks.Length, 1 To 2)
        For i = 0 To caseLinks.Length - 1
           linksAndIds(i + 1, 1) = caseLinks.item(i)
           linksAndIds(i + 1, 2) = Replace$(caseLinks.item(i), "https://crashviewer.nhtsa.dot.gov/nass-cds/CaseForm.aspx?xsl=main.xsl&CaseID=", vbNullString)
        Next

        .Quit
    End With
    GetLinksAndIds = linksAndIds
End Function

All Internet Explorer option:

Option Explicit

Public Sub GetTables()
    Dim sResponse As String, html As HTMLDocument, clipboard As Object, ws As Worksheet
    Dim initialLinksURL As String, i As Long, j As Long, newURL As String
    Set ws = ThisWorkbook.Worksheets("Sheet1")
    Set clipboard = GetObject("New:{1C3B4210-F441-11CE-B9EA-00AA006B1A69}")
    Set html = New HTMLDocument
    initialLinksURL = "https://crashviewer.nhtsa.dot.gov/LegacyCDS/Search"

    Dim ie As InternetExplorer, caseLinks As Object
    Set ie = New InternetExplorer
    With ie
        .Visible = True
        .Navigate2 initialLinksURL

        While .Busy Or .readyState < 4: DoEvents: Wend

        .document.getElementById("btnSubmit1").Click

        While .Busy Or .readyState < 4: DoEvents: Wend

        Set caseLinks = .document.querySelectorAll("[href*='CaseID=']")

        Dim linksAndIds()
        ReDim linksAndIds(1 To caseLinks.Length, 1 To 2)
        For i = 0 To caseLinks.Length - 1
            linksAndIds(i + 1, 1) = caseLinks.item(i)
            linksAndIds(i + 1, 2) = Replace$(caseLinks.item(i), "https://crashviewer.nhtsa.dot.gov/nass-cds/CaseForm.aspx?xsl=main.xsl&CaseID=", vbNullString)
        Next

        For i = LBound(linksAndIds, 2) To 2      ' UBound(linksAndIds, 2)

            newURL = "https://crashviewer.nhtsa.dot.gov/nass-cds/CaseForm.aspx?ViewPage&xsl=Case.xsl&tab=Crash&form=CaseForm&baseNode=&vehnum=-1&occnum=-1&pos=-1&pos2=-1&websrc=true&title=Crash%20Overview%20-%20Summary&caseid=" & linksAndIds(i, 2) & "&year=&fullimage=false"
            .Navigate2 newURL

            While .Busy Or .readyState < 4: DoEvents: Wend

            Dim tables As Object

            Set tables = .document.querySelectorAll("table")

            For j = 0 To tables.Length - 1
                clipboard.SetText tables.item(j).outerHTML
                clipboard.PutInClipboard
                ws.Cells(LastRow(ws) + 2, 1).PasteSpecial
            Next
        Next

        .Quit
    End With
End Sub

'https://www.rondebruin.nl/win/s9/win005.htm

Public Function LastRow(ByVal sh As Worksheet) As Long
    On Error Resume Next
    LastRow = sh.Cells.Find(What:="*", _
                            After:=sh.Range("A1"), _
                            Lookat:=xlPart, _
                            LookIn:=xlFormulas, _
                            SearchOrder:=xlByRows, _
                            SearchDirection:=xlPrevious, _
                            MatchCase:=False).Row
    On Error GoTo 0
End Function


来源：https://stackoverflow.com/questions/53556096/vba-cannot-get-data-from-html-with-getelementsbytag-nor-getelementbyid

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html
vba
web-scraping
getelementbyid
getelementsbytagname
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