Github user andruhon commented on a diff in the pull request:
https://github.com/apache/wicket/pull/256#discussion_r161933625
--- Diff:
wicket-extensions/src/main/java/org/apache/wicket/extensions/ajax/markup/html/AjaxFileUploadBehavior.java
---
@@ -0,0 +1,156 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.wicket.extensions.ajax.markup.html;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import org.apache.commons.fileupload.FileItem;
+import org.apache.commons.fileupload.FileUploadException;
+import org.apache.wicket.Component;
+import org.apache.wicket.ajax.AjaxEventBehavior;
+import org.apache.wicket.ajax.AjaxRequestTarget;
+import org.apache.wicket.ajax.attributes.AjaxRequestAttributes;
+import org.apache.wicket.ajax.attributes.AjaxRequestAttributes.Method;
+import org.apache.wicket.markup.head.IHeaderResponse;
+import org.apache.wicket.markup.head.JavaScriptHeaderItem;
+import org.apache.wicket.markup.head.OnDomReadyHeaderItem;
+import org.apache.wicket.markup.html.form.upload.FileUpload;
+import org.apache.wicket.protocol.http.servlet.MultipartServletWebRequest;
+import org.apache.wicket.protocol.http.servlet.ServletWebRequest;
+import org.apache.wicket.request.resource.PackageResourceReference;
+import org.apache.wicket.request.resource.ResourceReference;
+import org.apache.wicket.util.lang.Args;
+import org.apache.wicket.util.lang.Bytes;
+
+/**
+ * Uploads files from a drop event.
+ *
+ * @author svenmeier
+ */
+public class AjaxFileUploadBehavior extends AjaxEventBehavior
+{
+
+ private static final ResourceReference JS = new
PackageResourceReference(AjaxFileUploadBehavior.class, "datatransfer.js");
+
+ /**
+ * Maximum size of all uploaded files in bytes in a request.
+ */
+ private Bytes maxSize;
+
+ /**
+ * Maximum size of file of upload in bytes (if there are more than
one) in a request.
+ */
+ private Bytes fileMaxSize;
+
+ private String parameterName = "f";
+
+ public AjaxFileUploadBehavior()
+ {
+ super("drop");
+ }
+
+ @Override
+ public void renderHead(Component component, IHeaderResponse response)
+ {
+ super.renderHead(component, response);
+
+ response.render(JavaScriptHeaderItem.forReference(JS));
+
+ // default must be prevented for dragover event, otherwise
browser will consume the dataTransfer
+
response.render(OnDomReadyHeaderItem.forScript(String.format("jQuery('#%s').on('dragover',
function(e) { e.preventDefault(); });", component.getMarkupId())));
+ }
+
+ @Override
+ protected void updateAjaxAttributes(AjaxRequestAttributes attributes)
+ {
+ super.updateAjaxAttributes(attributes);
+
+ attributes.setMultipart(true);
+ attributes.setMethod(Method.POST);
+ // default must be prevented, otherwise browser will consume
the dataTransfer
+ attributes.setPreventDefault(true);
+
+ attributes.getDynamicExtraParameters().add(
+ String.format("return
Wicket.DataTransfer.getFilesAsParamArray(attrs.event.originalEvent, '%s');",
parameterName)
+ );
+ }
+
+ @Override
+ protected void onEvent(AjaxRequestTarget target)
+ {
+ try
+ {
+ ServletWebRequest request =
(ServletWebRequest)getComponent().getRequest();
+ final MultipartServletWebRequest multipartWebRequest =
request.newMultipartWebRequest(
+ getMaxSize(), getComponent().getPage().getId());
+ multipartWebRequest.setFileMaxSize(getFileMaxSize());
+ multipartWebRequest.parseFileParts();
+
+ // TODO: Can't this be detected from header?
+
getComponent().getRequestCycle().setRequest(multipartWebRequest);
+
+ ArrayList<FileUpload> fileUploads = new ArrayList<>();
+
+ // Get the item for the path
+ final List<FileItem> fileItems =
multipartWebRequest.getFile(parameterName);
+
+ if (fileItems != null)
+ {
+ for (FileItem item : fileItems)
+ {
+ fileUploads.add(new FileUpload(item));
+ }
+ }
+
+ onFileUpload(target, fileUploads);
+ }
+ catch (final FileUploadException fux)
+ {
+ onError(fux);
+ }
+ }
+
+ public Bytes getMaxSize()
+ {
+ return maxSize;
+ }
+
+ public void setMaxSize(Bytes maxSize)
+ {
+ Args.notNull(maxSize, "maxSize");
+ this.maxSize = maxSize;
+ }
+
+ public Bytes getFileMaxSize()
+ {
+ return fileMaxSize;
--- End diff --
I think these `getFileMaxSize` and `getSize` should either be abstract or
have a default value, otherwise it's currently can lead to
```
java.lang.IllegalArgumentException: Argument 'maxSize' may not be null.
at org.apache.wicket.util.lang.Args.notNull(Args.java:41)
~[wicket-util-8.0.0-SNAPSHOT.jar:8.0.0-SNAPSHOT]
at
org.apache.wicket.protocol.http.servlet.MultipartServletWebRequest.setMaxSize(MultipartServletWebRequest.java:121)
~[wicket-core-8.0.0-SNAPSHOT.jar:8.0.0-SNAPSHOT]
```
---
