AJAX Web Scraping and Interacting with Digg

You may download a free trial version of the WebRobot v1.1 component here, to test this project.

Interacting with sites that use JavaScript to generate content has, until now, been either very complex, or almost impossible. This tutorial will demonstrate the usage of the WebRobot v1.1 component to interact with the social bookmarking site digg, which employs JavaScript heavily to generate the displayed content, and to interact with it.

First, we will create our instance of the WebRobot component, and enable AJAX mode:

Private wrobot As New foxtrot.xray.WebRobot

Private Sub Form1_Load(ByVal sender As System.Object, _

ByVal e As System.EventArgs) Handles MyBase.Load

wrobot.AJAX = True

End Sub

Private Sub Form1_Closing(ByVal sender As Object, _

ByVal e As System.ComponentModel.CancelEventArgs) _

Handles MyBase.Closing

wrobot.Dispose()

End Sub

We created our instance of the WebRobot, enabled AJAX mode, and then, on the Closing event of our form, we called the Dispose metod to release all resources. Now, we will log in to digg:

'Load the main digg page

wrobot.LoadPage("http://digg.com")

'Get the login form

Dim loginform As foxtrot.xray.Form = wrobot.GetFormByContainsAction("login")

'Username field

Dim userfield As foxtrot.xray.Input.Text = loginform.Fields(0)

'Password field

Dim pswdfield As foxtrot.xray.Input.Password = loginform.Fields(1)

'Submit button

Dim sbmtfield As foxtrot.xray.Input.Submit = loginform.Fields(3)

userfield.Value = username

pswdfield.Value = password

'Simulate a click on the submit button

sbmtfield.Click()

After loading the main page, and filling out the login form, we clicked on the submit button. We could have used the WebRobot's SubmitForm method, but since this page may use JavaScript for form and button events, it would be safer to just simulate a click, so that any code gets interpreted. The Click event blocks until all actions are performed and any necessary page navigation is complete.

Now, we can start parsing through the main page content, to detect all the news items displayed. The WebRobot v1.1 component has an Element object and a FindElements method that allow sifting through the page. The Event object also exposes a Click method, to allow clicking on the elements you find after parsing. Let's look for news items:

Dim newsitems As New System.Collections.ArrayList

'Get the list of DIV elements on the web page

Dim elements() As foxtrot.xray.Element = wrobot.FindElements("div")

For Each item As foxtrot.xray.Element In elements

'Remove the CR and LF characters at the start of the element that the

'digg html source contains

Dim text As String = item.Text.TrimStart(vbCrLf.ToCharArray()).ToLower

'Look for DIVs of news-summary class

If (text.IndexOf("<div class=news-summary") = 0) Then

newsitems.Add(item)

End If

Now, we have the DIVs containing our news items. Note the use of the Text property of the elements to search for the class of the DIV.

Now that we have our list of DIVs, we will parse the content from them:

For Each newsitem As foxtrot.xray.Element In newsitems

'Object to store parsed article info

Dim artinfo As New ArticleInfo

'Get the H3s in the item, to look for the title

Dim titledata() As foxtrot.xray.Element = newsitem.FindElements("H3")

'The first H3 contains the title, now find the A HREF containing

'the news link

Dim urldata() As foxtrot.xray.Element = titledata(0).FindElements("A")

'The first A HREF found contains the news link

Dim ahref As String = urldata(0).Text

'Regular expression to get the URL and the title of the story

Dim parser As New _

System.Text.RegularExpressions.Regex("href=""(.*)"".*>(.*)</", _

System.Text.RegularExpressions.RegexOptions.IgnoreCase Or _

System.Text.RegularExpressions.RegexOptions.Singleline)

'Store the URL and title

artinfo.URL = parser.Matches(ahref).Item(0).Groups.Item(1).Value

artinfo.Title = parser.Matches(ahref).Item(0).Groups.Item(2).Value

'More parsing code follows

We found the URL and title of the story by searching within the DIV. Now, we will find the amount of diggs, the digg This! link, and the digg discussion for each news item:

'The amount of diggs is contained in a STRONG element. Find the one

'with a class that matches diggs-strong-

Dim digginfo() As foxtrot.xray.Element = newsitem.FindElements("strong")

For Each item As foxtrot.xray.Element In digginfo

Dim text As String = item.Text.TrimStart(vbCrLf.ToCharArray()).ToLower

If (text.IndexOf("<strong id=diggs-strong-") = 0) Then

parser = New System.Text.RegularExpressions.Regex(">(.*)</", _

System.Text.RegularExpressions.RegexOptions.IgnoreCase Or _

System.Text.RegularExpressions.RegexOptions.Singleline)

'Store the diggs count

artinfo.Diggs = _

Integer.Parse(parser.Matches(text).Item(0).Groups.Item(1).Value)

End If

'The digg this! link and the digg discussion links are stored in A HREFs

urldata = newsitem.FindElements("A")

For Each item As foxtrot.xray.Element In urldata

If (item.Text.IndexOf("digg it") > -1) Then

'If item contains digg it, it's the digg this! link.

'If the user has already dugg the item, this link will

'not be present. If present, we will store the Element

'object to simulate a click

artinfo.DiggLink = item

ElseIf (item.Text.IndexOf("class=more") > -1) Then

'If the A HREF class is more, then this is the digg discussion link

parser = New System.Text.RegularExpressions.Regex("href=""(.*)"".*>(.*)</", _

System.Text.RegularExpressions.RegexOptions.IgnoreCase Or _

System.Text.RegularExpressions.RegexOptions.Singleline)

artinfo.DiggMore = parser.Matches(item.Text).Item(0).Groups.Item(1).Value

End If

'Create a new item for the main article ListView

Dim litem As New ListViewItem(artinfo.Title)

'Store the article info in the articlelist HashTable

articlelist(litem) = artinfo

ListView1.Items.Add(litem)

We have populated our form with the article info. Now, we add code to load a web browser instance with the link story that was clicked on:

Private Sub ListView1_DoubleClick(ByVal sender As Object, _

ByVal e As System.EventArgs) Handles ListView1.DoubleClick

'Are there any selected items?

If (ListView1.SelectedItems.Count > 0) Then

'Get the article info related to the selected item

Dim item As ListViewItem = ListView1.SelectedItems(0)

Dim artinfo As ArticleInfo = articlelist(item)

'Launch a new web browser instance with the URL

System.Diagnostics.Process.Start(artinfo.URL)

End If

End Sub

Now, we create a context menu, to be displayed whenever the user right-clicks on an article. This context menu will show the amount of diggs (in MenuItem1), enable the user to digg the story (in MenuItem2), and also launch a browser instance with the digg discussion (in MenuItem3). First, we will add code to update the digg count and wether the news item has been dugg or not:

Private Sub ListView1_Click(ByVal sender As Object, _

ByVal e As System.EventArgs) Handles ListView1.Click

'Is there a selected item?

If (ListView1.SelectedItems.Count > 0) Then

'Enable the context menu

ListView1.ContextMenu = ContextMenu1

'Get the article info related to the selected item

Dim item As ListViewItem = ListView1.SelectedItems(0)

Dim artinfo As ArticleInfo = articlelist(item)

'Update digg count

MenuItem1.Text = artinfo.Diggs.ToString & " Diggs"

'Can we digg this item?

If (artinfo.DiggLink Is Nothing) Then

'Item already dugg

MenuItem2.Text = "Dugg!"

MenuItem2.Enabled = False

Else

'We can dig this item

MenuItem2.Text = "Digg this!"

MenuItem2.Enabled = True

End If

Else

'Disable the context menu

ListView1.ContextMenu = Nothing

End If

End Sub

Now, we can add code to digg a news item:

Private Sub MenuItem2_Click(ByVal sender As System.Object, _

ByVal e As System.EventArgs) Handles MenuItem2.Click

'Is there a selected item?

If (ListView1.SelectedItems.Count > 0) Then

ListView1.ContextMenu = ContextMenu1

'Get the article info related to the selected item

Dim item As ListViewItem = ListView1.SelectedItems(0)

Dim artinfo As ArticleInfo = articlelist(item)

'Are we sure we can digg this item?

If Not (artinfo.DiggLink Is Nothing) Then

'Simulate a click on the digg this! link, which

'contains JavaScript code, but no valid HREF

artinfo.DiggLink.Click()

'Clear this item so that we cannot try to digg it

'again, update digg count, and update the user

'interface

artinfo.DiggLink = Nothing

artinfo.Diggs += 1

MenuItem2.Text = "Dugg!"

MenuItem2.Enabled = False

MenuItem1.Text = artinfo.Diggs.ToString & " Diggs"

End If

End Sub

Finally, we add code to load a browser window with the digg discussion link:

Private Sub MenuItem3_Click(ByVal sender As System.Object, _

ByVal e As System.EventArgs) Handles MenuItem3.Click

'Are there any selected items?

If (ListView1.SelectedItems.Count > 0) Then

'Get the article info related to the selected item

Dim item As ListViewItem = ListView1.SelectedItems(0)

Dim artinfo As ArticleInfo = articlelist(item)

'Launch a new web browser instance with the digg discussion

System.Diagnostics.Process.Start(artinfo.DiggMore)

End If

End Sub

We have interacted with digg, simulating a real user clicking on links. Short of captchas, there is no way for a web application to know that it's not a real user at the helm.

1 Comment

Join the conversation! Your thoughts help the community grow.

Sam Hobbs14y ago
What does WebRobot do that cannot be done usiing the DOM? I have not looked at your article closely, but I suspect that this could also be done using the libraries described in my article about web site scraping. Generation of the web site by JavaScript would require handling events but I assume that WebRobot does not do anything that cannot be dne using the DOM. I assume that WebRobot uses the DOM and might be a good place to begin learning web seb scraping technology. Also I assume WebRobot is browser-independent but for browser clients that is usually not important since most scrapers do the navigation.