在 GWT 中使用 servlet 下载文件后表单操作没有停止？
Form action didn't rest after downloading file with servlets in GWT?
我在 GWT 中开发了一个小应用程序，在进行一些操作后上传和下载文件，它工作正常，但是下载文件后加载对话框图像永远不会停止，请指教。
客户端代码
public class Firstmodule implements EntryPoint
{
public void onModuleLoad()
{
final PopupPanel popup = new PopupPanel(false, true); // Create a modal dialog box that will not auto-hide
final FileUpload fileUpload = new FileUpload();
final FormPanel form = new FormPanel();
VerticalPanel vPanel = new VerticalPanel();
Image img = new Image("download.png");
vPanel.add(img);
form.setMethod(FormPanel.METHOD_POST);
// The HTTP request is encoded in multipart format.
form.setEncoding(FormPanel.ENCODING_MULTIPART);
form.setTitle("Family_Common_Fet");
form.setAction(GWT.getHostPageBaseURL() + "FileUploadGreeting");
form.setWidget(vPanel);
fileUpload.setName("uploader");
vPanel.add(fileUpload);
vPanel.setSpacing(20);
Label maxUpload = new Label();
maxUpload.setText("Text input file header: Datasheet, Vendor Code");
vPanel.add(maxUpload);
final Button submit = new Button("Upload and Run");
vPanel.add(submit);
submit.addClickHandler(new ClickHandler() {
public void onClick(ClickEvent event)
{
String filename = fileUpload.getFilename();
if(!filename.endsWith(".txt"))
{
System.out.println(filename);
Window.alert("only *.txt files accepted");
return;
}
else if(filename.length() == 0)
{
Window.alert("Please Select Text File");
return;
}
else
{
// loading dialog image
popup.add(new Image("loading_animation1.gif"));
popup.setGlassEnabled(true); // Enable the glass panel
popup.center(); // Center the popup and make it visible
submit.setEnabled(false);
submit.setFocus(true);
form.submit();
}
}
});
// Add an event handler to the form.
form.addSubmitHandler(new FormPanel.SubmitHandler() {
public void onSubmit(SubmitEvent event)
{
// This event is fired just before the form is submitted. We can take
// this opportunity to perform validation.
}
});
form.addSubmitCompleteHandler(new FormPanel.SubmitCompleteHandler() {
public void onSubmitComplete(SubmitCompleteEvent event)
{
//trying to stop the loading dialodg
popup.setGlassEnabled(false);
submit.setEnabled(true);
form.reset();
}
});
DecoratorPanel decPanel = new DecoratorPanel();
decPanel.setWidget(form);
RootPanel.get("uploadContainer").add(decPanel);
}
servlet 代码
public class UploadFileHandler extends HttpServlet
{
private static final long serialVersionUID = 1L;
public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
System.out.println("Inside doPost");
// Create a factory for disk-based file items
FileItemFactory factory = new DiskFileItemFactory();
// Create a new file upload handler
ServletFileUpload fileUpload = new ServletFileUpload(factory);
// sizeMax - The maximum allowed size, in bytes. The default value of -1 indicates, that there is no limit.
// 1048576 bytes = 1024 Kilobytes = 1 x 10 Megabyte
fileUpload.setSizeMax(10485760);
System.out.println(request.getRemoteAddr());
if(!ServletFileUpload.isMultipartContent(request))
{
try
{
throw new FileUploadException("error multipart request not found");
}catch(FileUploadException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
}
try
{
List<FileItem> items = fileUpload.parseRequest(request);
if(items == null)
{
response.getWriter().write("File not correctly uploaded");
return;
}
Iterator<FileItem> iter = items.iterator();
String absofilepath = null;
String fileName = null;
String filepath = "temp//fileOutput_" + System.currentTimeMillis() + ".txt";
while(iter.hasNext())
{
FileItem item = (FileItem) iter.next();
////////////////////////////////////////////////
// http://commons.apache.org/fileupload/using.html
////////////////////////////////////////////////
// if (item.isFormField()) {
fileName = item.getName();
System.out.println("fileName is : " + fileName);
String typeMime = item.getContentType();
System.out.println("typeMime is : " + typeMime);
int sizeInBytes = (int) item.getSize();
System.out.println("Size in bytes is : " + sizeInBytes);
// byte[] file = item.get();
absofilepath = getServletContext().getRealPath(filepath);
item.write(new File(absofilepath));
// }
}
String request_ip = getClientIpAddr(request);
System.out.println("Request IP:" + request_ip);
String tempoutFile = "output//" + fileName + System.currentTimeMillis() + ".txt";
String absooutFile = getServletContext().getRealPath(tempoutFile);
System.out.println("ouput file : " + absooutFile);
//************ some other operations in code*******///
}catch(Exception e){
e.printStackTrace();
PrintWriter out = response.getWriter();
response.setHeader("Content-Type", "text/html");
out.println("an Error has occuredin Exporter.bat" + e);
out.flush();
out.close();
}
// ****************************Downlaod **********************************//
downloadFile(request, response, absooutFile);
/*when i sing hashed code below it's return error in console and didn't stop the loading dialog image */
// PrintWriter out = response.getWriter();
// response.setHeader("Content-Type", "text/html");
// out.println("Check output File");
// System.out.println("Upload Ok");
// out.flush();
// out.close();
}catch(SizeLimitExceededException e)
{
System.out.println("File size exceeds the limit : 10 MB!!");
PrintWriter out = response.getWriter();
response.setHeader("Content-Type", "text/html");
out.println("Maximum file size should not exceed 10MB!!");
out.flush();
out.close();
}catch(Exception e)
{
e.printStackTrace();
PrintWriter out = response.getWriter();
response.setHeader("Content-Type", "text/html");
out.println("an Error has occured");
out.flush();
out.close();
}
}
public static String getClientIpAddr(HttpServletRequest request)
{
String ip = request.getHeader("X-Forwarded-For");
if(ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip))
{
ip = request.getHeader("Proxy-Client-IP");
}
if(ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip))
{
ip = request.getHeader("WL-Proxy-Client-IP");
}
if(ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip))
{
ip = request.getHeader("HTTP_CLIENT_IP");
}
if(ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip))
{
ip = request.getHeader("HTTP_X_FORWARDED_FOR");
}
if(ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip))
{
ip = request.getRemoteAddr();
}
return ip;
}
private void downloadFile(HttpServletRequest req, HttpServletResponse resp, String filePath)
{
try
{
File f = new File(filePath);
int length = 0;
ServletOutputStream op = resp.getOutputStream();
ServletContext context = getServletConfig().getServletContext();
String mimetype = context.getMimeType(filePath);
resp.setContentType((mimetype != null) ? mimetype : "application/octet-stream");
resp.setContentLength((int) f.length());
resp.setHeader("Content-Disposition", "attachment; filename=Fam_Com_Fet.txt");
DataInputStream in = new DataInputStream(new FileInputStream(f));
byte[] bbuf = new byte[in.available()];
while((in != null) && ((length = in.read(bbuf)) != -1))
{
op.write(bbuf, 0, length);
}
in.close();
op.flush();
op.close();
// f.delete();
}catch(IOException ioe)
{
ioe.printStackTrace();
}
}
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
doPost(request, response);
}
谢谢
SubmitCompleteHandler 仅保证在服务器发回 HTML 时调用，（请参阅 javadoc）它不适用于任意文件下载。
谢谢 Thomas Broyer Said 先生，我会在得到它时使用正确的代码来说明它。
开始时，当我在服务器端的 servlet 中使用以下代码时，响应返回到客户端，因此客户端不会再次执行任何内容，因为它已经请求返回（丢失请求）。
// ****************************Downlaod **********************************//
downloadFile(request, response, absooutFile);
所以使用技术的正确方法允许从客户端触发下载文件操作以保持（请求，响应）激活，这样它将能够完成我的操作代码
所以客户端代码会像这样
public class MainGUI extends VerticalPanel implements ClickHandler, SubmitCompleteHandler
{
private FormPanel form = new FormPanel();
private HTML descriptionLbl = new HTML("Please browse a text <B>[*.txt]</B> file with header : Datasheet , Vendor code ");
private HorizontalPanel hPanel = new HorizontalPanel();
private FileUpload fileUploader = new FileUpload();
private Button validateBtn = new Button("Import and download");
private Label errorLbl = new Label("Error message will be here");
private Image img = new Image("download.png");
private MyDialog loadingDialog;
private LoadingDialog ldialog;
public MainGUI()
{
setSpacing(5);
hPanel.setSpacing(5);
errorLbl.setStyleName("error");
form.setMethod(FormPanel.METHOD_POST);
form.setEncoding(FormPanel.ENCODING_MULTIPART);
form.setTitle("Fam_Com_Fet");
form.addSubmitCompleteHandler(this);
validateBtn.addClickHandler(this);
fileUploader.setName("uploader");
hPanel.add(fileUploader);
add(img);
setSpacing(20);
add(hPanel);
add(validateBtn);
add(errorLbl);
add(descriptionLbl);
form.add(this);
}
@Override
public void onClick(ClickEvent event)
{
exportcommonfeature();
}
private void exportcommonfeature()
{
errorLbl.setText("");
String fileName = fileUploader.getFilename();
if(fileName == null || fileName.isEmpty())
{
errorLbl.setText("No File Specified");
return;
}
if(!fileName.endsWith(".txt"))
{
errorLbl.setText("only *.txt files accepted");
return;
}
ldialog = new LoadingDialog();
// send the input to the server.
form.setAction(GWT.getHostPageBaseURL() + "UploadFileHandler");
form.submit();
}
@Override
public void onSubmitComplete(SubmitCompleteEvent event)
{
form.reset();
if("Error".equalsIgnoreCase(getPlainTextResult(event)))
{
errorLbl.setText("Error occured while exporting");
}else
{
/********************* 下载请求将在此处触发 ***************** ****/
form.setAction(GWT.getHostPageBaseURL() + "UploadFileHandler?command=download&filepath="+getPlainTextResult(event));
form.submit();
}
UploadFileHandler：正在映射 URL 我的 servlet 名称
download : 是 UploadFileHandler servlet 中用于下载文件的方法
ldialog.hide();
}
private String getPlainTextResult(SubmitCompleteEvent event)
{
HTML html = new HTML(event.getResults());
System.out.println("MainGUI File Path: " + html.getText());
return html.getText();
}
public FormPanel getFormPanel()
{
return this.form;
}
}
和 servlet 代码
public class UploadFileHandler extends HttpServlet
{
private static final long serialVersionUID = 1L;
public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
String filePath = request.getParameter("filepath");
String commandName = request.getParameter("command");
if("download".equalsIgnoreCase(commandName))
{
downloadFile(request, response, filePath);
}
else
generateResultFile(request, response);
}
public void generateResultFile(HttpServletRequest request, HttpServletResponse response){
System.out.println("Inside doPost");
// Create a factory for disk-based file items
FileItemFactory factory = new DiskFileItemFactory();
// Create a new file upload handler
ServletFileUpload fileUpload = new ServletFileUpload(factory);
// sizeMax - The maximum allowed size, in bytes. The default value of -1 indicates, that there is no limit.
// 1048576 bytes = 1024 Kilobytes = 1 x 10 Megabyte
fileUpload.setSizeMax(10485760);
System.out.println(request.getRemoteAddr());
if(!ServletFileUpload.isMultipartContent(request))
{
try
{
throw new FileUploadException("error multipart request not found");
}catch(FileUploadException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
}
try
{
List<FileItem> items = fileUpload.parseRequest(request);
if(items == null)
{
response.getWriter().write("File not correctly uploaded");
return;
}
Iterator<FileItem> iter = items.iterator();
String absofilepath = null;
String fileName = null;
String filepath = "temp//usrinpute_" + System.currentTimeMillis() + ".txt";
while(iter.hasNext())
{
FileItem item = (FileItem) iter.next();
////////////////////////////////////////////////
// http://commons.apache.org/fileupload/using.html
////////////////////////////////////////////////
// if (item.isFormField()) {
fileName = item.getName();
System.out.println("fileName is : " + fileName);
String typeMime = item.getContentType();
System.out.println("typeMime is : " + typeMime);
int sizeInBytes = (int) item.getSize();
System.out.println("Size in bytes is : " + sizeInBytes);
// byte[] file = item.get();
absofilepath = getServletContext().getRealPath(filepath);
item.write(new File(absofilepath));
// }
}
String request_ip = getClientIpAddr(request);
System.out.println("Request IP:" + request_ip);
String tempoutFile = "output//" + fileName + System.currentTimeMillis() + ".txt";
String absooutFile = getServletContext().getRealPath(tempoutFile);
System.out.println("ouput file : " + absooutFile);
// **************************************************************************************//
response.getWriter().write(absooutFile);
// ****************************End Loader**********************************//
//downloadFile(request, response, absooutFile);
}catch(SizeLimitExceededException e)
{
System.out.println("File size exceeds the limit : 10 MB!!");
PrintWriter out = null;
try
{
out = response.getWriter();
}catch(IOException e1)
{
// TODO Auto-generated catch block
e1.printStackTrace();
}
response.setHeader("Content-Type", "text/html");
out.println("Maximum file size should not exceed 10MB!!");
out.flush();
out.close();
}catch(IOException e)
{
try
{
response.getWriter().write("Error");
}catch(IOException ioe)
{
ioe.printStackTrace();
}
e.printStackTrace();
}catch(Exception e)
{
try
{
response.getWriter().write("Error");
}catch(IOException ioe)
{
ioe.printStackTrace();
}
e.printStackTrace();
}
}
public static String getClientIpAddr(HttpServletRequest request)
{
String ip = request.getHeader("X-Forwarded-For");
if(ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip))
{
ip = request.getHeader("Proxy-Client-IP");
}
if(ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip))
{
ip = request.getHeader("WL-Proxy-Client-IP");
}
if(ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip))
{
ip = request.getHeader("HTTP_CLIENT_IP");
}
if(ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip))
{
ip = request.getHeader("HTTP_X_FORWARDED_FOR");
}
if(ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip))
{
ip = request.getRemoteAddr();
}
return ip;
}
private void downloadFile(HttpServletRequest req, HttpServletResponse resp, String filePath)
{
try
{
File f = new File(filePath);
int length = 0;
ServletOutputStream op = resp.getOutputStream();
ServletContext context = getServletConfig().getServletContext();
String mimetype = context.getMimeType(filePath);
resp.setContentType((mimetype != null) ? mimetype : "text/plain");
resp.setContentLength((int) f.length());
resp.setHeader("Content-Disposition", "attachment; filename=Family_Common_Features.txt");
DataInputStream in = new DataInputStream(new FileInputStream(f));
byte[] bbuf = new byte[in.available()];
while((in != null) && ((length = in.read(bbuf)) != -1))
{
op.write(bbuf, 0, length);
}
in.close();
op.flush();
op.close();
// f.delete();
}catch(IOException ioe)
{
ioe.printStackTrace();
}
}
}
模块加载时class
public class Firstmodule implements EntryPoint
{
private MainGUI famLayout = new MainGUI();
public void onModuleLoad()
{
loadingGUI();
}
/**
* The message displayed to the user when the server cannot be reached or returns an error.
*/
static final String SERVER_ERROR = "An error occurred while " + "attempting to contact the server. Please check your network " + "connection and try again.";
private void loadingGUI()
{
VerticalPanel Layout = new VerticalPanel();
Layout.add(famLayout.getFormPanel());
Layout.setSpacing(30);
DecoratorPanel decPanel = new DecoratorPanel();
decPanel.setWidget(Layout);
decPanel.setWidth("60%");
decPanel.setHeight("90%");
RootPanel.get("uploadContainer").add(decPanel);
}
}
正在加载用于测试响应的对话框class 将继续
public class LoadingDialog extends PopupPanel
{
public LoadingDialog(){
setGlassEnabled(true);
setWidget(new Image("loading_animation1.gif"));
center();
}
}
这里还有 servlet 映射
<servlet>
<servlet-name>UploadFileHandler</servlet-name>
<servlet-class>edu.file.upload.com.server.UploadFileHandler</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>UploadFileHandler</servlet-name>
<url-pattern>/FileUploadGreeting</url-pattern>
</servlet-mapping>
编辑@21-12-2016
只需您可以在服务器端和 onSuccess 下载您的文件
使用此表单面板
FormPanel form = new FormPanel();
form.setMethod(FormPanel.METHOD_POST);
form.setAction(GWT.getHostPageBaseURL() + "ServletMappedName?command=download&filePath=" + filePath);
RootPanel.get().add(form);
form.submit();
我在 GWT 中开发了一个小应用程序，在进行一些操作后上传和下载文件，它工作正常，但是下载文件后加载对话框图像永远不会停止，请指教。
客户端代码
public class Firstmodule implements EntryPoint
{
public void onModuleLoad()
{
final PopupPanel popup = new PopupPanel(false, true); // Create a modal dialog box that will not auto-hide
final FileUpload fileUpload = new FileUpload();
final FormPanel form = new FormPanel();
VerticalPanel vPanel = new VerticalPanel();
Image img = new Image("download.png");
vPanel.add(img);
form.setMethod(FormPanel.METHOD_POST);
// The HTTP request is encoded in multipart format.
form.setEncoding(FormPanel.ENCODING_MULTIPART);
form.setTitle("Family_Common_Fet");
form.setAction(GWT.getHostPageBaseURL() + "FileUploadGreeting");
form.setWidget(vPanel);
fileUpload.setName("uploader");
vPanel.add(fileUpload);
vPanel.setSpacing(20);
Label maxUpload = new Label();
maxUpload.setText("Text input file header: Datasheet, Vendor Code");
vPanel.add(maxUpload);
final Button submit = new Button("Upload and Run");
vPanel.add(submit);
submit.addClickHandler(new ClickHandler() {
public void onClick(ClickEvent event)
{
String filename = fileUpload.getFilename();
if(!filename.endsWith(".txt"))
{
System.out.println(filename);
Window.alert("only *.txt files accepted");
return;
}
else if(filename.length() == 0)
{
Window.alert("Please Select Text File");
return;
}
else
{
// loading dialog image
popup.add(new Image("loading_animation1.gif"));
popup.setGlassEnabled(true); // Enable the glass panel
popup.center(); // Center the popup and make it visible
submit.setEnabled(false);
submit.setFocus(true);
form.submit();
}
}
});
// Add an event handler to the form.
form.addSubmitHandler(new FormPanel.SubmitHandler() {
public void onSubmit(SubmitEvent event)
{
// This event is fired just before the form is submitted. We can take
// this opportunity to perform validation.
}
});
form.addSubmitCompleteHandler(new FormPanel.SubmitCompleteHandler() {
public void onSubmitComplete(SubmitCompleteEvent event)
{
//trying to stop the loading dialodg
popup.setGlassEnabled(false);
submit.setEnabled(true);
form.reset();
}
});
DecoratorPanel decPanel = new DecoratorPanel();
decPanel.setWidget(form);
RootPanel.get("uploadContainer").add(decPanel);
}
servlet 代码
public class UploadFileHandler extends HttpServlet
{
private static final long serialVersionUID = 1L;
public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
System.out.println("Inside doPost");
// Create a factory for disk-based file items
FileItemFactory factory = new DiskFileItemFactory();
// Create a new file upload handler
ServletFileUpload fileUpload = new ServletFileUpload(factory);
// sizeMax - The maximum allowed size, in bytes. The default value of -1 indicates, that there is no limit.
// 1048576 bytes = 1024 Kilobytes = 1 x 10 Megabyte
fileUpload.setSizeMax(10485760);
System.out.println(request.getRemoteAddr());
if(!ServletFileUpload.isMultipartContent(request))
{
try
{
throw new FileUploadException("error multipart request not found");
}catch(FileUploadException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
}
try
{
List<FileItem> items = fileUpload.parseRequest(request);
if(items == null)
{
response.getWriter().write("File not correctly uploaded");
return;
}
Iterator<FileItem> iter = items.iterator();
String absofilepath = null;
String fileName = null;
String filepath = "temp//fileOutput_" + System.currentTimeMillis() + ".txt";
while(iter.hasNext())
{
FileItem item = (FileItem) iter.next();
////////////////////////////////////////////////
// http://commons.apache.org/fileupload/using.html
////////////////////////////////////////////////
// if (item.isFormField()) {
fileName = item.getName();
System.out.println("fileName is : " + fileName);
String typeMime = item.getContentType();
System.out.println("typeMime is : " + typeMime);
int sizeInBytes = (int) item.getSize();
System.out.println("Size in bytes is : " + sizeInBytes);
// byte[] file = item.get();
absofilepath = getServletContext().getRealPath(filepath);
item.write(new File(absofilepath));
// }
}
String request_ip = getClientIpAddr(request);
System.out.println("Request IP:" + request_ip);
String tempoutFile = "output//" + fileName + System.currentTimeMillis() + ".txt";
String absooutFile = getServletContext().getRealPath(tempoutFile);
System.out.println("ouput file : " + absooutFile);
//************ some other operations in code*******///
}catch(Exception e){
e.printStackTrace();
PrintWriter out = response.getWriter();
response.setHeader("Content-Type", "text/html");
out.println("an Error has occuredin Exporter.bat" + e);
out.flush();
out.close();
}
// ****************************Downlaod **********************************//
downloadFile(request, response, absooutFile);
/*when i sing hashed code below it's return error in console and didn't stop the loading dialog image */
// PrintWriter out = response.getWriter();
// response.setHeader("Content-Type", "text/html");
// out.println("Check output File");
// System.out.println("Upload Ok");
// out.flush();
// out.close();
}catch(SizeLimitExceededException e)
{
System.out.println("File size exceeds the limit : 10 MB!!");
PrintWriter out = response.getWriter();
response.setHeader("Content-Type", "text/html");
out.println("Maximum file size should not exceed 10MB!!");
out.flush();
out.close();
}catch(Exception e)
{
e.printStackTrace();
PrintWriter out = response.getWriter();
response.setHeader("Content-Type", "text/html");
out.println("an Error has occured");
out.flush();
out.close();
}
}
public static String getClientIpAddr(HttpServletRequest request)
{
String ip = request.getHeader("X-Forwarded-For");
if(ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip))
{
ip = request.getHeader("Proxy-Client-IP");
}
if(ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip))
{
ip = request.getHeader("WL-Proxy-Client-IP");
}
if(ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip))
{
ip = request.getHeader("HTTP_CLIENT_IP");
}
if(ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip))
{
ip = request.getHeader("HTTP_X_FORWARDED_FOR");
}
if(ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip))
{
ip = request.getRemoteAddr();
}
return ip;
}
private void downloadFile(HttpServletRequest req, HttpServletResponse resp, String filePath)
{
try
{
File f = new File(filePath);
int length = 0;
ServletOutputStream op = resp.getOutputStream();
ServletContext context = getServletConfig().getServletContext();
String mimetype = context.getMimeType(filePath);
resp.setContentType((mimetype != null) ? mimetype : "application/octet-stream");
resp.setContentLength((int) f.length());
resp.setHeader("Content-Disposition", "attachment; filename=Fam_Com_Fet.txt");
DataInputStream in = new DataInputStream(new FileInputStream(f));
byte[] bbuf = new byte[in.available()];
while((in != null) && ((length = in.read(bbuf)) != -1))
{
op.write(bbuf, 0, length);
}
in.close();
op.flush();
op.close();
// f.delete();
}catch(IOException ioe)
{
ioe.printStackTrace();
}
}
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
doPost(request, response);
}
谢谢
SubmitCompleteHandler 仅保证在服务器发回 HTML 时调用，（请参阅 javadoc）它不适用于任意文件下载。
谢谢 Thomas Broyer Said 先生，我会在得到它时使用正确的代码来说明它。
开始时，当我在服务器端的 servlet 中使用以下代码时，响应返回到客户端，因此客户端不会再次执行任何内容，因为它已经请求返回（丢失请求）。
// ****************************Downlaod **********************************//
downloadFile(request, response, absooutFile);
所以使用技术的正确方法允许从客户端触发下载文件操作以保持（请求，响应）激活，这样它将能够完成我的操作代码
所以客户端代码会像这样
public class MainGUI extends VerticalPanel implements ClickHandler, SubmitCompleteHandler
{
private FormPanel form = new FormPanel();
private HTML descriptionLbl = new HTML("Please browse a text <B>[*.txt]</B> file with header : Datasheet , Vendor code ");
private HorizontalPanel hPanel = new HorizontalPanel();
private FileUpload fileUploader = new FileUpload();
private Button validateBtn = new Button("Import and download");
private Label errorLbl = new Label("Error message will be here");
private Image img = new Image("download.png");
private MyDialog loadingDialog;
private LoadingDialog ldialog;
public MainGUI()
{
setSpacing(5);
hPanel.setSpacing(5);
errorLbl.setStyleName("error");
form.setMethod(FormPanel.METHOD_POST);
form.setEncoding(FormPanel.ENCODING_MULTIPART);
form.setTitle("Fam_Com_Fet");
form.addSubmitCompleteHandler(this);
validateBtn.addClickHandler(this);
fileUploader.setName("uploader");
hPanel.add(fileUploader);
add(img);
setSpacing(20);
add(hPanel);
add(validateBtn);
add(errorLbl);
add(descriptionLbl);
form.add(this);
}
@Override
public void onClick(ClickEvent event)
{
exportcommonfeature();
}
private void exportcommonfeature()
{
errorLbl.setText("");
String fileName = fileUploader.getFilename();
if(fileName == null || fileName.isEmpty())
{
errorLbl.setText("No File Specified");
return;
}
if(!fileName.endsWith(".txt"))
{
errorLbl.setText("only *.txt files accepted");
return;
}
ldialog = new LoadingDialog();
// send the input to the server.
form.setAction(GWT.getHostPageBaseURL() + "UploadFileHandler");
form.submit();
}
@Override
public void onSubmitComplete(SubmitCompleteEvent event)
{
form.reset();
if("Error".equalsIgnoreCase(getPlainTextResult(event)))
{
errorLbl.setText("Error occured while exporting");
}else
{
/********************* 下载请求将在此处触发 ***************** ****/
form.setAction(GWT.getHostPageBaseURL() + "UploadFileHandler?command=download&filepath="+getPlainTextResult(event));
form.submit();
}
UploadFileHandler：正在映射 URL 我的 servlet 名称
download : 是 UploadFileHandler servlet 中用于下载文件的方法
ldialog.hide();
}
private String getPlainTextResult(SubmitCompleteEvent event)
{
HTML html = new HTML(event.getResults());
System.out.println("MainGUI File Path: " + html.getText());
return html.getText();
}
public FormPanel getFormPanel()
{
return this.form;
}
}
和 servlet 代码
public class UploadFileHandler extends HttpServlet
{
private static final long serialVersionUID = 1L;
public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
String filePath = request.getParameter("filepath");
String commandName = request.getParameter("command");
if("download".equalsIgnoreCase(commandName))
{
downloadFile(request, response, filePath);
}
else
generateResultFile(request, response);
}
public void generateResultFile(HttpServletRequest request, HttpServletResponse response){
System.out.println("Inside doPost");
// Create a factory for disk-based file items
FileItemFactory factory = new DiskFileItemFactory();
// Create a new file upload handler
ServletFileUpload fileUpload = new ServletFileUpload(factory);
// sizeMax - The maximum allowed size, in bytes. The default value of -1 indicates, that there is no limit.
// 1048576 bytes = 1024 Kilobytes = 1 x 10 Megabyte
fileUpload.setSizeMax(10485760);
System.out.println(request.getRemoteAddr());
if(!ServletFileUpload.isMultipartContent(request))
{
try
{
throw new FileUploadException("error multipart request not found");
}catch(FileUploadException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
}
try
{
List<FileItem> items = fileUpload.parseRequest(request);
if(items == null)
{
response.getWriter().write("File not correctly uploaded");
return;
}
Iterator<FileItem> iter = items.iterator();
String absofilepath = null;
String fileName = null;
String filepath = "temp//usrinpute_" + System.currentTimeMillis() + ".txt";
while(iter.hasNext())
{
FileItem item = (FileItem) iter.next();
////////////////////////////////////////////////
// http://commons.apache.org/fileupload/using.html
////////////////////////////////////////////////
// if (item.isFormField()) {
fileName = item.getName();
System.out.println("fileName is : " + fileName);
String typeMime = item.getContentType();
System.out.println("typeMime is : " + typeMime);
int sizeInBytes = (int) item.getSize();
System.out.println("Size in bytes is : " + sizeInBytes);
// byte[] file = item.get();
absofilepath = getServletContext().getRealPath(filepath);
item.write(new File(absofilepath));
// }
}
String request_ip = getClientIpAddr(request);
System.out.println("Request IP:" + request_ip);
String tempoutFile = "output//" + fileName + System.currentTimeMillis() + ".txt";
String absooutFile = getServletContext().getRealPath(tempoutFile);
System.out.println("ouput file : " + absooutFile);
// **************************************************************************************//
response.getWriter().write(absooutFile);
// ****************************End Loader**********************************//
//downloadFile(request, response, absooutFile);
}catch(SizeLimitExceededException e)
{
System.out.println("File size exceeds the limit : 10 MB!!");
PrintWriter out = null;
try
{
out = response.getWriter();
}catch(IOException e1)
{
// TODO Auto-generated catch block
e1.printStackTrace();
}
response.setHeader("Content-Type", "text/html");
out.println("Maximum file size should not exceed 10MB!!");
out.flush();
out.close();
}catch(IOException e)
{
try
{
response.getWriter().write("Error");
}catch(IOException ioe)
{
ioe.printStackTrace();
}
e.printStackTrace();
}catch(Exception e)
{
try
{
response.getWriter().write("Error");
}catch(IOException ioe)
{
ioe.printStackTrace();
}
e.printStackTrace();
}
}
public static String getClientIpAddr(HttpServletRequest request)
{
String ip = request.getHeader("X-Forwarded-For");
if(ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip))
{
ip = request.getHeader("Proxy-Client-IP");
}
if(ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip))
{
ip = request.getHeader("WL-Proxy-Client-IP");
}
if(ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip))
{
ip = request.getHeader("HTTP_CLIENT_IP");
}
if(ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip))
{
ip = request.getHeader("HTTP_X_FORWARDED_FOR");
}
if(ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip))
{
ip = request.getRemoteAddr();
}
return ip;
}
private void downloadFile(HttpServletRequest req, HttpServletResponse resp, String filePath)
{
try
{
File f = new File(filePath);
int length = 0;
ServletOutputStream op = resp.getOutputStream();
ServletContext context = getServletConfig().getServletContext();
String mimetype = context.getMimeType(filePath);
resp.setContentType((mimetype != null) ? mimetype : "text/plain");
resp.setContentLength((int) f.length());
resp.setHeader("Content-Disposition", "attachment; filename=Family_Common_Features.txt");
DataInputStream in = new DataInputStream(new FileInputStream(f));
byte[] bbuf = new byte[in.available()];
while((in != null) && ((length = in.read(bbuf)) != -1))
{
op.write(bbuf, 0, length);
}
in.close();
op.flush();
op.close();
// f.delete();
}catch(IOException ioe)
{
ioe.printStackTrace();
}
}
}
模块加载时class
public class Firstmodule implements EntryPoint
{
private MainGUI famLayout = new MainGUI();
public void onModuleLoad()
{
loadingGUI();
}
/**
* The message displayed to the user when the server cannot be reached or returns an error.
*/
static final String SERVER_ERROR = "An error occurred while " + "attempting to contact the server. Please check your network " + "connection and try again.";
private void loadingGUI()
{
VerticalPanel Layout = new VerticalPanel();
Layout.add(famLayout.getFormPanel());
Layout.setSpacing(30);
DecoratorPanel decPanel = new DecoratorPanel();
decPanel.setWidget(Layout);
decPanel.setWidth("60%");
decPanel.setHeight("90%");
RootPanel.get("uploadContainer").add(decPanel);
}
}
正在加载用于测试响应的对话框class 将继续
public class LoadingDialog extends PopupPanel
{
public LoadingDialog(){
setGlassEnabled(true);
setWidget(new Image("loading_animation1.gif"));
center();
}
}
这里还有 servlet 映射
<servlet>
<servlet-name>UploadFileHandler</servlet-name>
<servlet-class>edu.file.upload.com.server.UploadFileHandler</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>UploadFileHandler</servlet-name>
<url-pattern>/FileUploadGreeting</url-pattern>
</servlet-mapping>
编辑@21-12-2016 只需您可以在服务器端和 onSuccess 下载您的文件 使用此表单面板
FormPanel form = new FormPanel();
form.setMethod(FormPanel.METHOD_POST);
form.setAction(GWT.getHostPageBaseURL() + "ServletMappedName?command=download&filePath=" + filePath);
RootPanel.get().add(form);
form.submit();