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Java program to download images from website and display file sizes

I am creating a java program that will read an html document from a url and display the dimensions of the images in code. I'm not sure how to do this though.

I wouldn't need to actually load and save the images, I just need the dimensions and the order in which they appear on the web page.

eg: web page has 3 images

<img src="dog.jpg" /> //which is 54kb
<img src="cat.jpg" /> //which is 75kb
<img src="horse.jpg"/> //which is 80kb

I will need the output of my java program to display

54kb
75kb
80kb

Any ideas where I should start?

ps I'm a bit new to java

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4 answers


If you are new to Java, you may need to use an existing library to make things a little easier. Jsoup allows you to fetch HTML page and fetch elements using CSS style selectors.

This is just a quick and very dirty example, but I think it will show how easy Jsoup can accomplish such a task. Note that error handling and response code handling have been omitted, I just wanted to convey the general idea:



Document doc = Jsoup.connect("http://stackoverflow.com/questions/14541740/java-program-to-download-images-from-a-website-and-display-the-file-sizes").get();

Elements imgElements = doc.select("img[src]");
Map<String, String> fileSizeMap = new HashMap<String, String>();

for(Element imgElement : imgElements){
    String imgUrlString = imgElement.attr("abs:src");
    URL imgURL = new URL(imgUrlString);
    HttpURLConnection httpConnection = (HttpURLConnection) imgURL.openConnection();
    String contentLengthString = httpConnection.getHeaderField("Content-Length");
    if(contentLengthString == null)
        contentLengthString = "Unknown";

    fileSizeMap.put(imgUrlString, contentLengthString);
}

for(Map.Entry<String, String> mapEntry : fileSizeMap.entrySet()){
    String imgFileName = mapEntry.getKey();
    System.out.println(imgFileName + " ---> " + mapEntry.getValue() + " bytes");
}

You can also consider Apache HttpClient . I find this is generally preferred over the original URLConnection / HttpURLConnection approach.

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You have to break your problem into 3 sub problems



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You can use regular expressions to find the tag and get the image url. After that you need the HttpUrlConnection class to get the image data and measure its size.

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You can do it:

try {
    URL urlConn = new URL("http://yoururl.com/cat.jpg");
    URLConnection urlC = urlConn.openConnection();
    System.out.println(urlC.getContentLength());
} catch (MalformedURLException e) {
    e.printStackTrace();
} catch (IOException e) {
    e.printStackTrace();
}
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