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copied!<blockquote> <p><em>I've seen some suggestions like having the image directory being a symbolic link pointing to a directory outside the web container, but will this approach work both on Windows and *nix environments?</em></p> </blockquote> <p>If you adhere the *nix filesystem path rules (i.e. you use exclusively forward slashes as in <code>/path/to/files</code>), then it will work on Windows as well without the need to fiddle around with ugly <code>File.separator</code> string-concatenations. It would however only be scanned on the same working disk as from where this command is been invoked. So if Tomcat is for example installed on <code>C:</code> then the <code>/path/to/files</code> would actually point to <code>C:\path\to\files</code>.</p> <p>If the files are all located outside the webapp, and you want to have Tomcat's <code>DefaultServlet</code> to handle them, then all you basically need to do in Tomcat is to add the following Context element to <code>/conf/server.xml</code> inside <code><Host></code> tag:</p> <pre class="lang-xml prettyprint-override"><code><Context docBase="/path/to/files" path="/files" /> </code></pre> <p>This way they'll be accessible through <code>http://example.com/files/...</code>. GlassFish/Payara configuration example can be found <a href="https://stackoverflow.com/questions/19981640/how-to-display-images-located-in-glass-fish-folder">here</a> and WildFly configuration example can be found <a href="https://stackoverflow.com/questions/34426082/how-can-i-serve-static-resources-from-outside-a-war-on-wildfly">here</a>.</p> <p>If you want to have control over reading/writing files yourself, then you need to create a <code>Servlet</code> for this which basically just gets an <code>InputStream</code> of the file in flavor of for example <code>FileInputStream</code> and writes it to the <code>OutputStream</code> of the <code>HttpServletResponse</code>.</p> <p>On the response, you should set the <code>Content-Type</code> header so that the client knows which application to associate with the provided file. And, you should set the <code>Content-Length</code> header so that the client can calculate the download progress, otherwise it will be unknown. And, you should set the <code>Content-Disposition</code> header to <code>attachment</code> if you want a <em>Save As</em> dialog, otherwise the client will attempt to display it inline. Finally just write the file content to the response output stream.</p> <p>Here's a basic example of such a servlet:</p> <pre><code>@WebServlet("/files/*") public class FileServlet extends HttpServlet { @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String filename = URLDecoder.decode(request.getPathInfo().substring(1), "UTF-8"); File file = new File("/path/to/files", filename); response.setHeader("Content-Type", getServletContext().getMimeType(filename)); response.setHeader("Content-Length", String.valueOf(file.length())); response.setHeader("Content-Disposition", "inline; filename=\"" + file.getName() + "\""); Files.copy(file.toPath(), response.getOutputStream()); } } </code></pre> <p>When mapped on an <code>url-pattern</code> of for example <code>/files/*</code>, then you can call it by <code>http://example.com/files/image.png</code>. This way you can have more control over the requests than the <code>DefaultServlet</code> does, such as providing a default image (i.e. <code>if (!file.exists()) file = new File("/path/to/files", "404.gif")</code> or so). Also using the <code>request.getPathInfo()</code> is preferred above <code>request.getParameter()</code> because it is more SEO friendly and otherwise IE won't pick the correct filename during <em>Save As</em>.</p> <p>You can reuse the same logic for serving files from database. Simply replace <code>new FileInputStream()</code> by <code>ResultSet#getInputStream()</code>.</p> <p>Hope this helps.</p> <h3>See also:</h3> <ul> <li><a href="https://stackoverflow.com/questions/18664579/recommended-way-to-save-uploaded-files-in-a-servlet-application">Recommended way to save uploaded files in a servlet application</a></li> <li><a href="https://stackoverflow.com/questions/132052/servlet-for-serving-static-content/29991447#29991447">Abstract template for a static resource servlet</a> (supporting HTTP cache)</li> <li><a href="https://stackoverflow.com/questions/2340406/how-to-retrieve-and-display-images-from-a-database-in-a-jsp-page">How to retrieve and display images from a database in a JSP page?</a></li> <li><a href="https://stackoverflow.com/questions/13588149/how-to-stream-audio-video-files-such-as-mp3-mp4-avi-etc-using-a-servlet">How to stream audio/video files such as MP3, MP4, AVI, etc using a Servlet</a></li> </ul>

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