java - 使用 gwt 上传不正确

Question

我遇到了 gwt-upload 的问题：我需要 onChange Upload 才能从 db 获取我的对象；如果存在，Web 应用程序可以使用 Servlet 上传文件，否则将显示警报。

带有注释的代码仅在带有“It works”注释的位置运行。

为什么它不在 else 块中运行？

final MultiUploader upload = new MultiUploader(FileInputType.BUTTON);
upload.addOnChangeUploadHandler(new OnChangeUploaderHandler() {

    @Override
    public void onChange(IUploader uploader) {
        myService.getMyObject(name, new AsyncCallback<List<Object>>() {

            @Override
            public void onFailure(Throwable caught) {
                Window.alert("Something");
            }

            @Override
            public void onSuccess(List<Object> listMyObject) {
                if(listMyObject.size() == 0) {
                    Window.alert("Error.");
                } else {
                    //It doesn't works.
                    String url = GWT.getModuleBaseURL() + "upload?nameObject=" + name;
                    upload.setServletPath(url);
                }
            }
        });
    }
});
//It works.
String url = GWT.getModuleBaseURL() + "upload?nameObject=" + name;
upload.setServletPath(url);

Answer 1

您可以通过添加上传按钮并在服务器调用成功时提交上传者表单来解决此问题。这是有关如何执行此操作的概述。阅读gwtupload 文档以在 web.xml 中添加 servlet 映射。

Uploader uploader = new Uploader(FileInputType.BROWSER_INPUT);
uploader.setServletPath("myservletpath");
uploader.setAutoSubmit(false);
uploader.setEnabled(true);

Button uploadButton = new Button("Upload");
uploadButton.addClickHandler(new ClickHandler()){
    myService.getMyObject(name, new AsyncCallback<List<Object>>() {

            @Override
            public void onFailure(Throwable caught) {
                //do something
            }

            @Override
            public void onSuccess(List<Object> listMyObject) {
                //do something if condition satisfies then submit
                if(conditionSatifies){
                    uploader.submit();
                }else{
                    //do something, prompt a message
                }
            }
     });
}