Question

我创建了widget，我直接添加到根面板

public class FileUploadWidget extends VerticalPanel {
    public FileUploadWidget() {
        super();
        final FormPanel form = new FormPanel();

        form.setMethod(FormPanel.METHOD_POST);
        form.setEncoding(FormPanel.ENCODING_MULTIPART);
        form.setAction("/FileUpload"); 

        form.setWidget(this);

        final FileUpload fileUpload = new FileUpload();

        fileUpload.setName("uploadFormElement");  
        this.add(fileUpload);

        Label maxUpload = new Label();
        maxUpload.setText("Maximum upload file size: 1MB");
        this.add(maxUpload);

        Button button = new Button("Submit");
        button.addClickHandler(new ClickHandler() {

            public void onClick(ClickEvent event) {
                form.submit();

            }
        });
        this.add(button);

        form.addSubmitCompleteHandler(new SubmitCompleteHandler() {

            public void onSubmitComplete(SubmitCompleteEvent event) {
                Window.alert(event.getResults());

            }
        });
    }

}

我创建了servlet

public class FileUploadServlet extends HttpServlet {

    private static final long serialVersionUID = 1L;

      protected void doPost(HttpServletRequest request, 
    HttpServletResponse response) 
          throws ServletException, IOException { 
        response.setContentType("text/plain"); 

        FileItem uploadItem = getFileItem(request); //BREAKPOINT

        if (uploadItem == null) { 
          response.getWriter().write("NO-SCRIPT-DATA"); 
          return; 
        } 
        try {
            uploadItem.write(new File("newfile.txt"));
        } catch (Exception e) {
            response.getWriter().write("ERROR");
        }

        response.getWriter().write("OK"); 
      } 

      private FileItem getFileItem(HttpServletRequest request) { 
        FileItemFactory factory = new DiskFileItemFactory(); 
        ServletFileUpload upload = new ServletFileUpload(factory); 

        try { 
          List items = upload.parseRequest(request); 
          Iterator it = items.iterator(); 
          while (it.hasNext()) { 
            FileItem item = (FileItem) it.next(); 
            if (!item.isFormField() 
                && "uploadFormElement".equals(item.getFieldName())) { 
              return item; 
            } 
          } 
        } catch (FileUploadException e) { 
          return null; 
        } 
        return null; 
      } 
     }

我把我的web.xml文件映射为servlet

<servlet>
    <servlet-name>FileUpload</servlet-name>
    <servlet-class>my.web.app.GwtFileUpload.server.FileUploadServlet</servlet-class>
</servlet>
 ....
<servlet-mapping>
    <servlet-name>FileUpload</servlet-name>
    <url-pattern>/FileUpload</url-pattern>
</servlet-mapping>

现在当我选择文件，然后调用提交，当我使用firefox时没有发生任何事情（我得到的只是SubmitEvent），我的断点，我在servlet代码中标记的永远不会到达

当我在chrome下尝试相同的代码时，它会进入servlet，但它没有找到任何文件

任何人都可以解释为什么会有这么不同的行为，以及我如何解决它？

Answer 1

FileUpload小部件包装HTML元素。如果要将此小部件提交给服务器，则必须与FormPanel一起使用。因此，有必要将fileupload添加到FormPanel。您已将其直接添加到Panel。请替换代码

this.add(fileUpload);

到

form.add(fileUpload);

有关详情，请仔细阅读http://www.tutorialspoint.com/gwt/gwt_fileupload_widget.htm

链接

Answer 2

将fileUpload控件添加到FormPanel，因为FileUpload widget（实现HasName的那些）将被提交到服务器（如果它们包含在此面板中）。

执行fileupload后，您已将form.setWidget(this);添加到Verticlepanel中。喜欢

this.add(fileUpload);
form.setWidget(this);

Answer 3

我建议使用gwtupload库，它可以节省大量时间编写自己的代码，并为您的应用提供许多功能，如自定义按钮，进度条，文件扩展名，大小限制等。

您拥有此GettingStarted和此example页。

文件上传不起作用

3 个答案: