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Java: Deleting file after download using PHP

I am currently developing an android app to download a file from server after which I need to delete it.
I've done a bit of Google and most of the solutions was to use the apache FTPClient. I personally prefer to use PHP to do the job but I have some concerns.
Can I and more importantly SHOULD I use PHP to delete said files? I would be passing the filename as POST data and not Query Strings. Will this be secure enough so people are unable to mess with my file system? Or will I need to watch out for other stuff

I am new to the php and i have not tried this but you should try this. Before downloading the file, get filename and store it in variable. Now after downloading file, search that file in the database and fire the query for deleting it.

How to save application data for use across users in OS X

I have a Mac Java application that needs to persist data across reboots. The data needs to be saved so that any user has access to it. E.g. an SQLite database file that can be used for all users.
It looks like the /Library/Application Support/ folder is supposed to be used for this, but I'm not able to write to it without making my app run as root or changing the permissions of the file to rwxrwxrwx.
What is the proper way to save application-level data on Mac?

The developer documentation covering this is a bit of a large topic:
https://developer.apple.com/library/Mac/referencelibrary/GettingStarted/GS_DataManagement_MacOSX/_index.html#//apple_ref/doc/uid/TP40009046
https://developer.apple.com/library/mac/documentation/FileManagement/Conceptual/FileSystemProgrammingGuide/Introduction/Introduction.html#//apple_ref/doc/uid/TP40010672
According to the File System Programming guide you should make a specific subdirectory inside /Library/Application\ Support for your app to store app data common to all users on the system. I'd use reverse domain name notation such as com.yourcompany.yourapp or something else unlikely to collide with another app's use of the common directory for this.
You might also look into using an existing app bundler for OS X such as https://bitbucket.org/infinitekind/appbundler rather than hard code paths to file locations.

Custom password encrypted file system for storing files in Android

is it possible to create a custom file system or use an existing file system like EncFs to read data inside Android environment.
My idea is to make a virtual filesystem for storing some media files and developing an app which can directly access those files from the filesystem volume.
I hope im clear with my question.!!

Yes, but you need a rooted devices to use it. Or, you need to build your own firmware. Here's one, it's open source: http://nemesis2.qx.net/pages/LUKSManager

Playing a sound file on website media player

Hey all, i'm new to web development so i'm really dumb when it comes to tools for working on it. I have .amr files recorded from my BB application that are sent and saved on a server. I want to be able to play these files via a webplayer on a website, I have a couple of questions regarding this:
1) Would it be sound to convert these files to something like mp3 o wav instead of trying to play using the amr format? The sound files are received by a java web service and saved as files on my hard drive with the URL saved on a MySQL database. So if a conversion method is suggested I would prefer it be in Java.
2) What player can I use and how, to play these files? Be it the amr files or converted files
3) How can I create a link that will point to said audio file so people can go to it and hear it? I know this differs a little from my original question line but I have to able to do it as well.
thanks in advance

1) MP3 or wav would be a good idea. You could use something like LAMEonJ (http://openinnowhere.sourceforge.net/lameonj/) for wav -> mp3. And with luck there's something similar for AMR.
2) Is the <audio> tag in HTML5 likely to be an option? The users could then play the file directly in the browser, and you could just render HTML on the website, rather than providing it through a webservice.
I think you are suggesting an applet on a web page, that connects to the server via a webservice, which would certainly be possible but a lot more work.
Otherwise, if you're just serving a music file, you're not going to be able to control what player is used on the client side, once they have your file they can do with it whatever they like.
The only down side of HTML5 is that they'll need a relatively recent browser.
3) If you're using <audio> then this is already taken care of.
If you google for the <audio> tag I think you'll find a lot of information,as well as strategies for providing alternative players to older browsers.

Multiple file uploader with previews

I'm trying to find something that will let users upload multiple files to a website. The requirements are that it let them easily select multiple files (preferably with something like check boxes) and that it displays a preview of the images they select.
I'd prefer to only use Javascript or Flash if possible, but Java is also an option (this needs to work on platforms where Silverlight isn't available).
So far all I've been able to find are things that use the native file selector (which doesn't show previews on Windows, and makes it unclear that you can select multiple by holding ctrl).
I'm not sure if the preview requirement is even possible, but it's the most important.

This is a firefox solution:
It uses the FileReader javascript object to load, display and upload images.
http://hacks.mozilla.org/2011/01/how-to-develop-a-html5-image-uploader/
It still doesnt show previews in the FileSelection dialog but at least allows you to preview the images before uploading.
And here is a ready made java applet solution:
http://jumploader.com/doc_overview.html

To upload multiple files I use RichFaces rich:fileUpload component.
Concerning the preview, I've got the similar problem and the best I found after couple of days of googling is following.
Alfresco has the same problem and resolved it with :
An open office which runs in server mode (socket) and all the office documents are sent by alfresco to open office in order to convert them in PDF
Those PDF are converted to .swf viewer thanks to SWFTOOLS
This .swf is integrated in the HTML
For images, it uses ImageMagick to create small version of the file I suppose
Personnaly, I will try to implement it this way :
Converting office documents to PDF thanks to open office in socket mode
Transform the first page of the PDF into a PNG thanks to JPedal library
Diplay that PNG to the end user
For images I would perhaps use ImageMagick too ... but for now, I'm using Seam Image.scaleToFit API

I am assuming 2 things here:
1) Some kind of client/enduser will be doing the file upload
2) You get some kind of say on what the client installs on their computer to help make this happen.
If this is the case, my first suggestion would be:
Give them FTP or SFTP client software to upload files. The php page you make can have a link to Filezilla, along with instructions on how to use it. ftp and sftp are THE protocols to use for transferring files. HTTP is just not designed(well) for it, nor are browsers.
Once the user has the (S)FTP client software installed, you can give them URL's to upload files to that are specific to their user account, and you can have a backend script process and load/move files that they upload. It's pretty easy to create a local temporary directory using a server side script, have the client upload files via ftp, then go back to the web browser and click a button that says "Done uploading, please process my stuff".
The browser can even give back confirmations on everything that gets uploaded/processed.