Can I get cached images using HttpClient?

问题

Is it possible to load login page once, using HttpClient, and get image file of img element from cache, not from src link, without reload? It is important because I need to save captcha for just loaded page, if I try load it from src link, it will be another captcha. I tried:

    DefaultHttpClient httpclient = new DefaultHttpClient();

    HttpGet httpget = new HttpGet("http://www.mysite/login.jsp");

    HttpResponse response = httpclient.execute(httpget);
    HttpEntity entity = response.getEntity();

    InputStream instream = entity.getContent();
    OutputStream outstream = new FileOutputStream("d://file.html");
    org.apache.commons.io.IOUtils.copy(instream, outstream);
    outstream.close();
    instream.close();

but there are not any images. I also tried HtmlUnitDriver from selenium library, there are not any images too. Maybe I must try something else? Can you help me with it?

Thanks and sorry for my English.

回答1:

As it mentioned here: HttpClient Get images from response the DefaultHttpClient/HttpClient get's only one content, which is in your case it's an HTML page (served from: http://www.mysite/login.jsp). Than you need to parse that HTML page and get the specified img tag with it's src than you need only to download it (ONLY that, without resend the login.jsp request!). If you download a captcha image you need to get that image as soon as possible or it could be overwritten by another user, who tries to login.

As the browser does, you need to do the same way, download HTML, than parse it, than request all src/link/ect depends on what you need.

DefaultHttpClient doesn't cache by default.

CachingHttpClient cache is enabled by default, in this case you need to analyzes If-Modified-Since and If-None-Match headers in order to decide if request to the remote server is performed, or if its result is returned from cache. If there's no change on the server, you will get cached data, if you cached previously.

来源：https://stackoverflow.com/questions/19201829/can-i-get-cached-images-using-httpclient

标签

java

apache-commons-httpclient