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how to check if a URL is valid before making a connection

Posted on 2006-10-24
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Last Modified: 2010-04-16
Hi guys

i have this code in which I check whether there is an image stored on the server or a link to an image is provided. Now what I need is that if the image link doesn't go to a valid image then it shouldn't show the image. Also when I write some random word a s a link to the image such as 'jsadsakd' it throws an error and doesn't display the whole page at all


her is my code
----------------------
 <% if(chapter_sponsor.getImage_size() > 0){%>
                                <td>
                                    <a href ="<%= chapter_sponsor.getImage_link() %>" target="_blank" ><img src="attachments/sponsors/<%=chapter_ID%><%=chapter_sponsor.getSponsor_ID()%>" border="0" width="200" height="100"></a>      
                                </td>
                                <%}else if(!checkNull(chapter_sponsor.getSponsor_image_url()).equals("")){
                                          URL img = new URL(chapter_sponsor.getSponsor_image_url());
                                          try{
                                                HttpURLConnection con = (HttpURLConnection )img.openConnection();
                                                if(con.getResponseCode()!=HttpURLConnection.HTTP_NOT_FOUND){%>
                                                      <td>
                                                      <a href ="<%= chapter_sponsor.getImage_link() %>" target="_blank" ><img src="<%=chapter_sponsor.getSponsor_image_url()%>" border="0" width="200" height="100"></a>      
                                                      </td>
                                         <%}}catch(IOException e)
                                    { %>
                                                <td>
                                                      <a href ="<%= chapter_sponsor.getImage_link() %>" target="_blank" ><img src="http://www.ccim.com/common/images/missing_photo.gif" border="0" width="200" height="100">
                                                </td>

                              <% }}%>
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Question by:huzefaq
2 Comments
 
LVL 41

Expert Comment

by:HonorGod
ID: 17798272
 Is this validation to be performed by the server?  You might try retrieving the image (on the server) before you put the image URL in the src attribute.
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LVL 3

Accepted Solution

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royce2020 earned 500 total points
ID: 17800447
You could try checking the link for the substing ".jpg"  for instance, the following function will return true if the link ends in a valid image extention, and false if something else (you could also add elements to ArrExtentions for more image types.):

function RealImg(strLink as string)
    ret = false
    ArrExtentions = array (".jpg",".jpeg",".gif",".png")
    for i = 0 to ubound (ArrExtentions) -1
        if lcase(left(strLink,(len(ArrExtentions(i))))) = ArrExtentions(i) then ret = true
    next i
    RealImg = ret
end function
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