Develop Reference

Apache Commons Net FTP does not throw any exception on wrong credentials

I just managed to upload some files to an FTP server using Apache Commons Net FTP. When I use everything as it should be it works fine, I mean, the file uploading is working, but when I use, for example, a wrong password for the FTP account, obviously the files don't get uploaded to the server, but I don't get an error message either. In other words: I don't know how to show the error. I tried to show with a toast the e.getMessage() from the Exception but nothing is shown. Is there any documentation that would help me? Or am I missing something you could help me with? thank you!
This is my code:
#Override
protected Void doInBackground(Void... voids) {
FTPClient ftpClient=new FTPClient();
try {
ftpClient.connect(fserver);
ftpClient.login(fusername,fpassword);
ftpClient.enterLocalPassiveMode();
dirArch = new ArrayList<>();
for (int k=0;k<adapter.getSelected().size();k++){
dirArch.add(adapter.getSelected().get(k).getArch());
}
for (String archTXT : dirArch){
File fileX =new File(stringFolder,archTXT);
InputStream inputStream=new FileInputStream(fileX);
ftpClient.storeFile(archTXT,inputStream);
inputStream.close();
pbPorc=pbPorc+pbSum;
pb1.setProgress(pbPorc);
pb2.setProgress(pbPorc);
}
ftpClient.logout();
ftpClient.disconnect();
} catch (IOException e) {
e.printStackTrace();
Toast.makeText(ExportTracks.this,e.getMessage(),Toast.LENGTH_LONG).show();
}
return null;
}

Your error handling is wrong.
The FTPClient.login does not throw an exception, when the credentials are wrong. It returns a false. You do not test for that. Your code carries on, trying to work with not authorized session instead, all of which will obviously fail too.
But as the same is true for FTPClient.storeFile, which also just returns false, your code basically does not notice any errors.

Thread problem with input stream from servlet request

I have brief understanding on multi threading in Java web apps. However, I came across an issue while developing our android app which communicates with the server via REST.
Our web application is based on Apache Wicket 8.6 and contains additional HttpServlet endpoints. One endpoint is applied while uploading images from the app via post. This works fine as long as I am uploading only one image at a time. If I perform multiple upload requests in my android app in a quick succession (some milliseconds), only the last upload is performed successfully (it is working fine when I put a second break between the uploads). It seems, as if all requests except the last one are missing the image content read from the input stream of the servlet request. Thus, I am guessing, that I am having a threading problem with my servlet. I would appreciate, if someone could guide me in the right direction to solve this issue.
public class MyServlet extends HttpServlet{
#Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
boolean proceed =true;
Map<String,String[]> parameters = req.getParameterMap();
if(parameters!=null){
//read some parameters which specify the request
}
if(proceed) {
InputStream is = req.getInputStream();
if(is!=null) {
//The result of this output is 0 for the first requests only for the last request it is 1
System.err.println("Stream size: "+is.available());
//do something
}
}
//do something....
}
}
I could, of course, write the images in my android app in one request using multipart but still I'd like to make the servlet thread safe for the occasion that it gets two requests at the same time.
I appreciate your help.

So, after some additional research I discovered, that the input stream is not empty even is.available() returns 0
My problem was something different. I save the uploaded image in a ModeShape repository. The repository session is stored in the wicket application instance. THus, only one ModeSHape repository session exists. When writing the image, it seems as if there was a problem with the ModeShape session. Thus, I put the ModeShape session in a synchronized block and now everything runs fine.
public class MyServlet extends HttpServlet{
#Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
boolean proceed =true;
Map<String,String[]> parameters = req.getParameterMap();
if(parameters!=null){
//read some parameters which specify the request
}
if(proceed) {
String fileName = req.getHeader("fileName");
if(!StringUtils.isEmpty(fileName)) {
InputStream is = req.getInputStream();
if(is!=null) {
//The result of this output is 0 for the first requests only for the last request it is 1
System.err.println("Stream size: "+is.available());
WicketApplication app=null;
try {
app = (WicketApplication)Application.get("wicket");
} catch (Exception e) {
LOG.error("Error while generating WicketApplication object for project "+project.getName(),e);
}
if(app!=null) {
final Session repoSession = app.getRepoSession();
synchronized (repoSession) {
//write image to repository
}
}
}
}
}
//do something....
}
}

I want to delete file from server using http doDelete() method

if i want to delete welcome.html file how to delete it using http doDelete() methode how to do it i am new to java so plz help me
public void doDelete(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
boolean success = false;
File file = null;
try {
file = searchFile(request);
} catch (Exception ex) {
java.util.logging.Logger.getLogger(Request.class.getName()).
log(java.util.logging.Level.SEVERE, null, ex);
}
if (!file.exists()) {
response.sendError(HttpServletResponse.SC_NOT_FOUND);
return;
} else {
success = file.delete(); // actual delete operation
}
if (success) {
response.setStatus(HttpServletResponse.SC_NO_CONTENT);
}
}
private String searchFile(HttpServletRequest req) throws Exception {
String fileName = req.getPathInfo();
fileName = fileName.substring(1);
return fileName;
}

While we wait for you to explain how your code "doesn't work" ... I should point out that if this code did work, it would be extremely dangerous.
Your code makes no attempt to check that the user (i.e. the guy sending the request) should be allowed to delete the file, or what the user is attempting to delete. If some bad guy sent you a DELETE request with ".."'s in it, they could probably trick your web server into attempting to delete any file in the file system!!! (Hopefully you never run your web servers as "root" ...)
UPDATE: The answer to your Question is simple. Change
file = searchFile(request);
to
file = new File(searchFile(request));
But that is the least of your problems!

GWT Catching exception thrown by HttpServlet

From the server Code (in an HttpServlet) I'm throwing an exception if the file is too large:
public void doPost(HttpServletRequest req, HttpServletResponse res)
throws ServletException, IOException {
...
// Check if the blob has correct size, otherwise delete it
final BlobInfo blobInfo = new BlobInfoFactory().loadBlobInfo(blobKey);
long size = blobInfo.getSize();
if(size > 0 && size <= BasicConstants.maxImageSize){
res.sendRedirect("/download?blob-key=" + blobKey.getKeyString());
} else { // size not allowed
bs.delete(blobKey);
throw new RuntimeException(BasicConstants.fileTooLarge);
}
From the client code I'm missing to successfully catch the exception with this snippet:
try {
uploadForm.submit(); // send file to BlobStore, where the doPost method is executed
} catch (Exception ex) {
GWT.log(ex.toString());
}
However, from this other client code snippet I'm somehow detecting when the exception was thrown with an ugly workaround that I don't trust at all:
uploadForm.addSubmitCompleteHandler(new FormPanel.SubmitCompleteHandler() {
#Override
public void onSubmitComplete(SubmitCompleteEvent event) {
// This is what gets the result back - the content-type *must* be
// text-html
String imageUrl =event.getResults();
// This ugly workaround apparently manages to detect when the server threw the exception
if (imageUrl.length() == 0) { // file is too large
uploadFooter.setText(BasicConstants.fileTooLarge);
} else { // file was successfully uploaded
...
}
The Development Mode view in Eclipse reports an error of type "uncaught exception", which suggests that I'm really doing a bad job at detecting it.
Can anyone tell me how to properly catch the exception, and if the workaround I'm using makes any sense?
Thanks!

Your first attempt
try {
uploadForm.submit(); // send file to BlobStore, where the doPost method is executed
} catch (Exception ex) {
GWT.log(ex.toString());
}
doesn't work, because submit() doesn't wait until the browser receives the response (it's an asynchronous call).
uploadForm.addSubmitCompleteHandler(new FormPanel.SubmitCompleteHandler() {
#Override
public void onSubmitComplete(SubmitCompleteEvent event) {
...
Here you actually receive the response from the server. But it's a form submission, not a GWT-RPC call, so the result is just plain text, not GWT Java Objects.
When you throw a RuntimeException in a Servlet, the server will simply send a response with an error code (probably '500', but ideally use the "Network" tab in Firebug or Chrome Developer Tools to see the actual response and response code.) So in the success case you'll get the URL, otherwise the response is empty.
Possible solution
You can catch Exceptions on the server side, and send better descriptions explicitly:
public void doPost(HttpServletRequest req, HttpServletResponse res)
throws ServletException, IOException {
try {
...
if (...) {
throw new MyTooLargeException();
} else {
...
res.getWriter().write("ok " + ...);
}
} catch (MyTooLargeException e) {
res.getWriter().write("upload_size_exceeded"); // just an example string
// (use your own)
res.sendError(HttpServletResponse.SC_REQUEST_ENTITY_TOO_LARGE);
}
}
Then, on the client, check for
"upload_size_exceeded".equals(event.getResults()).

Java/JSP Image upload. Where to keep these image files?

I am writing a simple application that lets a user upload images. After the upload, the user can tag them or remove them.
I figured out how to upload the files and save them once the files are uploaded. I am keeping tracking of a global path where images are kept. In the database I keep the meta data about the images like file name, tags, etc.
I am using Java/JSP (specifically Stripes framework but my problem is generic).
My question is where do I keep these image files once they are uploaded?
Right now I have two web applications deployed on a Tomcat server. One main web application and other one is the where I upload the images.
But this does not work as I can not see the uploaded images in the main application until I redeploy/restart Tomcat.
It seems like Tomcat does not pick newly uploaded images automatically.
Does anyone have any solutions?
This is a simple project, so I do not want to store them in a database or use Apache for images. That is all just too complicated for this small project.
Thanks.

Definitely don't store the images in the database, but you will want to store the image path in the database. This will allow you to store the image just about anywhere.
Since you are using two tomcat applications, your best bet may be to store the images outside of either app and stream the image back to the user instead of letting tomcat manage the files. Otherwise, I would ask why you are trying to do this with two web apps.

However, storing uploaded images inside the web-app directory is not a wise thing to do, and you know it.
By the way, you might want to look this stackoverflow thread, lately discussed where to store the images. It might not solve your issue, surely will give you more confidence on what you are doing.

I've solved this in different ways.
First, the non-portable way, is that Glassfish (and I do believe Tomcat as well) allows you to map an external directory in to the webapps hierarchy. This works really well and does exactly what you want. It lets you store your images in an external directory away from your webapp, yet still serve them up.
However, this technique is not portable.
The way to I've done it portably is by creating a filter.
You place the filter someplace obvious, say "/images".
What the filter does is this:
it checks for the image (or anything, it works with any static resource) in a special directory within the webapp. For our example we'll use the url "/webapp/images".
if the file DOES NOT exist, we copy the file from your external location in to the appropriate spot within the webapp. So, let's say the reqyest url is "/images/banner.gif". And that your files are stored on disk at "/home/app/images". So, our source file is "/home/app/images/banner.gif". We then copy it to where we want it in the webapp tree. We use "ServletContext.getRealPath" for this. So, the destination will be "ServletContext.get RealPath("/webapp/images/banner.gif"). Just copy the source to the destination.
if the file already existed, or now exists, simply forward to the actual image at /webapp/images/banner.gif.
Effectively you end up having a file cache within your webapps deployment tree. The down side is that it's a cache, so it needs to be maintained (i.e. you should check if the original is newer than your cache, make sure you delete if the source is deleted, etc.). Also, it duplicates your resources, so your images will consume, eventually, twice as much disk space. Finally, there's the initial copy cost at start up.
However, it DOES work, and it prevents you from having to serve up static resources using your own code. (Which is the 3rd solution, map a filter/servlet to intercept the URLs and simply stream it your self.)
I would look at the construct within Tomcat (assuming it exists) to do the mapping for you. I know it exists in Glassfish. (Google alternatedocroot for Glassfish to see how it works.)

I was using two web applications to avoid over writing the uploaded images in case I redeploy a new main application war file.
But as you mention there is no other option but to stream them through a Servlet or something I guess I can keep them outside tomcat directory.
I wanted to avoid writing this Streaming Servlet. Just too small project to deal with all the mess (like proper content type, 404, etc.) while writing the streaming servlet.

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Image streaming Servlet.
*/
public class ImageDisplayServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* #see HttpServlet#HttpServlet()
*/
public ImageDisplayServlet() {
super();
}
/**
* #see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String relativePath = trimToEmpty(request.getPathInfo());
// Make sure no one try to screw with us.
// This is important as user can literally access any file if we are not careful
if(isXSSAttack(relativePath) == false) {
String pathToFile = this.getServletContext().getRealPath(request.getPathInfo());
File file = new File(pathToFile);
System.out.println("Looking for file " + file.getAbsolutePath());
// show a 404 page
if(!file.exists() || !file.isFile()) {
httpError(404, response);
} else {
try {
streamImageFile(file, response);
} catch(Exception e) {
// Tell the user there was some internal server error.\
// 500 - Internal server error.
httpError(500, response);
e.printStackTrace();
}
}
} else {
// what to do if i think it is a XSS attack ?!?
}
}
private void streamImageFile(File file, HttpServletResponse response) {
// find the right MIME type and set it as content type
response.setContentType(getContentType(file));
BufferedInputStream bis = null;
BufferedOutputStream bos = null;
try {
response.setContentLength((int) file.length());
// Use Buffered Stream for reading/writing.
bis = new BufferedInputStream(new FileInputStream(file));
bos = new BufferedOutputStream(response.getOutputStream());
byte[] buff = new byte[(int) file.length()];
int bytesRead;
// Simple read/write loop.
while (-1 != (bytesRead = bis.read(buff, 0, buff.length))) {
bos.write(buff, 0, bytesRead);
}
} catch (Exception e) {
throw new RuntimeException(e);
} finally {
if (bis != null) {
try {
bis.close();
} catch (IOException e) {
e.printStackTrace();
// To late to do anything about it now, we may have already sent some data to user.
}
}
if (bos != null) {
try {
bos.close();
} catch (IOException e) {
e.printStackTrace();
// To late to do anything about it now, we may have already sent some data to user.
}
}
}
}
private String getContentType(File file) {
if(file.getName().length() > 0) {
String[] parts = file.getName().split("\\.");
if(parts.length > 0) {
// only last part interests me
String extention = parts[parts.length - 1];
if(extention.equalsIgnoreCase("jpg")) {
return "image/jpg";
} else if(extention.equalsIgnoreCase("gif")) {
return "image/gif";
} else if(extention.equalsIgnoreCase("png")) {
return "image/png";
}
}
}
throw new RuntimeException("Can not find content type for the file " + file.getAbsolutePath());
}
private String trimToEmpty(String pathInfo) {
if(pathInfo == null) {
return "";
} else {
return pathInfo.trim();
}
}
private void httpError(int statusCode, HttpServletResponse response) {
try {
response.setStatus(statusCode);
response.setContentType("text/html");
PrintWriter writer = response.getWriter();
writer.append("<html><body><h1>Error Code: " + statusCode + "</h1><body></html>");
writer.flush();
} catch (IOException e) {
e.printStackTrace();
}
}
private boolean isXSSAttack(String path) {
boolean xss = false;
// Split on the bases of know file separator
String[] parts = path.split("/|\\\\");
// Now verify that no part contains anything harmful
for(String part : parts) {
// No double dots ..
// No colons :
// No semicolons ;
if(part.trim().contains("..") || part.trim().contains(":") || part.trim().contains(";")) {
// Fire in the hole!
xss = true;
break;
}
}
return xss;
}
/**
* #see HttpServlet#doPost(Ht/promotions/some.jpgtpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}
Ok Here is a Servlet that I quickly wrote that can stream images:
Here is the List of limitations and know issues:
May have XSS vulnerability use with care
Not production ready use as reference
Images need to in the web application directory. Can be easily change but I too lazy (it is not worth it the project is too small)
Only stream jpg,gif or png files.
Usage:
Let say you deploy this web application called images as separate application.
http://www.example.com/images/promotions/promo.jpg
means there should be a directory in "promotions" with image "promo.jpg" with in this images web application.
PS: Do not ask why I am doing this Servlet Container only solution that sucks big time.

<servlet>
<description></description>
<display-name>ImageDisplayServlet</display-name>
<servlet-name>ImageDisplayServlet</servlet-name>
<servlet-class>com.example.images.ImageDisplayServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>ImageDisplayServlet</servlet-name>
<url-pattern>/*</url-pattern>
</servlet-mapping>
Oh ya configure your Servlet like above for best results :P