Gwt 文件

public void onModuleLoad() {
        final FormPanel form = new FormPanel();
        form.setAction("/upload");
        form.setEncoding(FormPanel.ENCODING_MULTIPART);
        form.setMethod(FormPanel.METHOD_POST);

        VerticalPanel panel = new VerticalPanel();
        form.setWidget(panel);

            // GWT 提供的 FileUpload 控件
        final FileUpload upload = new FileUpload();
        upload.setName("uploadFormElement");
        panel.add(upload);

        // Add a 'submit' button.
        panel.add(new Button("Submit", new ClickListener() {
          public void onClick(Widget sender) {
            form.submit();
          }
        }));

        // Add an event handler to the form.
        form.addFormHandler(new FormHandler() {
            public void onSubmit(FormSubmitEvent event) {
                    System.out.println(" ==== onSubmit ====");
                                        // upload.getFilename() 可以得到用户选择的文件路径和文件名
                    if (upload.getFilename().length() == 0) {
                        Window.alert("error!");
                        event.setCancelled(true);
                    } else if (!upload.getFilename().endsWith(".zip")) {
                        Window.alert("error.");
                        event.setCancelled(true);
                    }
                }


            public void onSubmitComplete(FormSubmitCompleteEvent event) {
                System.out.println(" ==== onSubmitComplete ====");
                System.out.println(event.getResults());
            }
        });

        RootPanel.get().add(form);
    }
    }