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

huzefaq
huzefaq asked
on
Medium Priority
223 Views
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>

                              <% }}%>
Comment
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HonorGodSoftware Engineer
CERTIFIED EXPERT

Commented:
 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.
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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