Upload handling
Your application may have forms with which visitors can upload images. For example, the State Department has an page for submitting a photograph when applying for passports.
In HTML development, uploading a file requires a form on the client with an attribute enctype="multipart/form-data", and the form itself contains an element <input type="file">.
In the following example, you implement a front-end form and back-end class that uploads an image and saves it using the default storage configuration defined in context.xml. The upload method from the browser is post.
Step 1: Implement HTML form
Implement an HTML form in a template.
HTML form for uploading a file:
<h2>Upload File</h2>
<form enctype="multipart/form-data" method="post" action="/upload-servlet">
<p><input type="file" name="file" /></p>
<p><input type="text" name="description" /></p>
<p><input type="submit" /></p>
</form>-
Provides the upload method (post) and specifies the back-end servlet processing the uploaded form (upload-servlet).
-
Provides the name attribute for the file in the uploaded form.
You鈥檒l use both of these attributes when implementing the upload servlet.
Step 2: Implement upload servlet
Implement a servlet that accepts the uploaded form and saves the image to storage.
import com.psddev.dari.util.ObjectUtils;
import com.psddev.dari.util.StorageItem;
import com.psddev.dari.util.StorageItemFilter;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
@WebServlet("/upload-servlet")
public class UploadServlet extends HttpServlet {
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
StorageItem storageItem = StorageItemFilter.getParameter(request,"file", null);
Map<String, Object> properties = new HashMap<String, Object>();
properties.put("path", storageItem.getPath());
properties.put("storageName", storageItem.getStorage());
response.setContentType("application/json");
PrintWriter out = response.getWriter();
out.print(ObjectUtils.toJson(properties));
out.flush();
}
}-
Associates the servlet with the action specified in "HTML form for uploading a file."
-
Overrides the
doPostmethod. We use this method because the upload form in "HTML form for uploading a file" specifiesmethod=post. -
Extracts the file from the form data using the value specified in the upload form name=file. The last parameter,
null, indicates Brightspot uses the default storage item configuration appearing in the Tomcatcontext.xmlfile. For information about configuring storage items, see Configuring StorageItem. -
Builds a map of key-value pairs describing the file鈥檚 storage characteristics. For additional methods available for examining the uploaded file, see .
-
Builds a JSON object from the map and returns it to the client.
{
"path": "33/c7/f340bec94c21b7e88687c4f78fa4/dragon-slayer.jpg",
"storageName": "tutorial.local"
}StorageItemFilter provides useful methods for extracting uploaded files from an uploaded form. For details, see .
See also: