上传文件时,我过去曾扩展HttpServlet。我与
Commons-FileUpload一起使用它。
我制作了一个通用的基于表单的上传小部件。这是为了适应不同文件类型(纯文本和Base64)的上传。如果您只需要上传纯文本文件,则可以将以下两个类合并为一个。
public class UploadFile extends Composite {
@UiField FormPanel uploadForm;
@UiField FileUpload fileUpload;
@UiField Button uploadButton;
interface Binder extends UiBinder<Widget, UploadFile> {}
public UploadFile() {
initWidget(GWT.<Binder> create(Binder.class).createAndBindUi(this));
fileUpload.setName("fileUpload");
uploadForm.setEncoding(FormPanel.ENCODING_MULTIPART);
uploadForm.setMethod(FormPanel.METHOD_POST);
uploadForm.addSubmitHandler(new SubmitHandler() {
@Override
public void onSubmit(SubmitEvent event) {
if ("".equals(fileUpload.getFilename())) {
Window.alert("No file selected");
event.cancel();
}
}
});
uploadButton.addClickHandler(new ClickHandler() {
@Override
public void onClick(ClickEvent event) {
uploadForm.submit();
}
});
}
public HandlerRegistration addCompletedCallback(
final AsyncCallback<String> callback) {
return uploadForm.addSubmitCompleteHandler(new SubmitCompleteHandler() {
@Override
public void onSubmitComplete(SubmitCompleteEvent event) {
callback.onSuccess(event.getResults());
}
});
}
}
UiBinder 部分非常简单。
<g:HTMLPanel>
<g:HorizontalPanel>
<g:FormPanel ui:field="uploadForm">
<g:FileUpload ui:field="fileUpload"></g:FileUpload>
</g:FormPanel>
<g:Button ui:field="uploadButton">Upload File</g:Button>
</g:HorizontalPanel>
</g:HTMLPanel>
现在您可以扩展此类,以用于纯文本文件。只需确保您的
web.xml
将HttpServlet服务于
/textupload
端点即可。
public class UploadFileAsText extends UploadFile {
public UploadFileAsText() {
uploadForm.setAction(GWT.getModuleBaseURL() + "textupload");
}
}
纯文本文件的Servlet位于服务器端。它将上传文件的内容返回给客户端。请确保在类路径上的某个位置安装了Apache Commons的FileUpload jar包。
public class TextFileUploadServiceImpl extends HttpServlet {
private static final long serialVersionUID = 1L;
@Override
protected void doPost(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException {
if (! ServletFileUpload.isMultipartContent(request)) {
response.sendError(HttpServletResponse.SC_BAD_REQUEST,
"Not a multipart request");
return;
}
ServletFileUpload upload = new ServletFileUpload();
try {
FileItemIterator iter = upload.getItemIterator(request);
if (iter.hasNext()) {
FileItemStream fileItem = iter.next();
ServletOutputStream out = response.getOutputStream();
response.setBufferSize(32768);
int bufSize = response.getBufferSize();
byte[] buffer = new byte[bufSize];
InputStream in = fileItem.openStream();
BufferedInputStream bis = new BufferedInputStream(in, bufSize);
long length = 0;
int bytes;
while ((bytes = bis.read(buffer, 0, bufSize)) >= 0) {
out.write(buffer, 0, bytes);
length += bytes;
}
response.setContentType("text/html");
response.setContentLength(
(length > 0 && length <= Integer.MAX_VALUE) ? (int) length : 0);
bis.close();
in.close();
out.flush();
out.close();
}
} catch(Exception caught) {
throw new RuntimeException(caught);
}
}
}
我不记得我是如何解决
标签的问题的。你可能需要在客户端过滤标签。这个话题也在
这里进行了讨论。