Is it possible to persuade the stream result to download an entire directory and it's contents? And if so, how? I've no problem getting it to download individual files, but I have a need to download a series of files that must be in a specific directory structure.
I don't think so.
Stream result allow you to download ONE content, with its MIME type, its name, etc.
This makes it impossible to work with a lot of files, with different names and content type.
What you can do is:
Render in a JSP the list of files (in anchor tags for example), everyone targeting the Action that will download that single file;
Call multiple Actions via scripting opening multiple pages (target="_blank") for every file you have (dangerous, annoying, almost useless...);
Create a zip with Java in server side, containing all your files and directories, then output the zip with Stream result.
I think you may consider the third option.
Related
I was asked to develop a game called "Flag Quiz" in which the player have to guess the correct name of the flag that appears in the middle of the screen.
Of course I have a lot of pictures (221 flags) and I have to put them inside the program because, when the button Play is pressed, the program has to pick randomly 10 of these flags.
Problem
I was thinking to use an ImageList but the flags are 480x311 and so Delphi asks me to separate the picutre in 30 different bitmaps. Can I do anything about this?
My idea, to avoid that problem, was the following (although I think that it's not very good): create 221 TPicture components (invisible to the user of course) and load in each of them a picture of a flag.
I'd prefer not using the last idea I had. Do you know any improvement?
This sort of problem is simply not suited to the form designer. You want to store 221 images, and managing that in the IDE will be horrible. Once you've got them all in you won't be able to see them readily because they will be base 16 encoded in a .dfm file. Under revision control it will be a mess because you won't be able to change individual images in a manageable and traceable manner.
The accepted way to do this is to use resources. If it were me, I'd arrange for my images to have predicatable names. For instance, flag1, flag2, etc. I'd generate a resource script (.rc) that listed all the flags. I'd compile that resource script to a compiled resource (.res) which is linked to the executable. I'd have the resource script and the image files committed to revision control.
Then at runtime you have a single TImage control to display the flag. Every time you need a new image you load it with TResourceStream, and push it into the TImage control.
Devexpress has a Componnect named cximagecolletion that you can put your images on it and save and load images from/to file
or you can save all flags in small access db and load it when you need using tadodataset
there is no doubt that if you put your images direct on your form your dfm grow very high and so you Get Into trouble
Personally I would store each file as an image in a dedicated subdirectory, using the country as a file name. Then I would read the subdirectory file names on entry to the program (so I have a list of countries that I can randomly choose from) and use TImage.LoadFromFile to display the flag. This is far easier to extend than using a resource file (IMHO).
I would like to create a file type with a personal extension by combining two other file types, like .mp3 and .pdf.
Later I need to re-open the custom files I've made and be able to use the included files in my app.
How do I do that on iOS?
One option is to append the data of the two files together. Include a few bytes of data at the start that tell you the size of each and maybe their original filenames. Then when you want to recreate the two files from the one custom one, you read your header to get the sizes and names, then use that info to recreate the original files.
Another option would be to zip the two files together. Just give the zip file your own custom extension.
Another option would be to use an NSFileWrapper. Include the two regular files in the wrapper.
I would like to create a simple file repository in Ruby on Rails. Users have their accounts, and after one logs in they can upload a file or download files previously uploaded.
The issue here is the security. Files should be safe and not available to anyone but the owners.
Where, in which folder, should I store the files, to make them as safe as possible?
Does it make sense, to rename the uploaded files, store the names in a database and restore them when needed? This might help avoid name conflicts, though I'm not sure if it's a good idea.
Should the files be stored all in one folder, or should they be somewhat divided?
rename the files, for one reason, because you have no way to know if today's file "test" is supposed to replace last week's "test" or not (perhaps the user had them in different directories)
give each user their own directory, this prevents performance problems and makes it easy to migrate, archive, or delete a single user
put metadata in the database and files in the file system
look out for code injection via file name
This is an interesting question. Depending on the level of security you want to apply I would recommend the following:
Choose a folder that is only accessible by your app server (if you chose to store in the FS)
I would always recommend to rename the files to a random generated hash (or incremntally generated name like used in URL shorteners, see the open source implementation of rubyurl). However, I wouldn't store them in a database because filesystems are built for handling files, so let it do the job. You should store the meta data in the database to be able to set the right file name when the user downloads the file.
You should partition the files among multiple folders. This gives you multiple advantages. First, filesystems are not built to handle millions of files in a single folder. If you have operations that try to get all files from a folder this takes significantly more time. If you obfuscate the original file name you could create one directory for each letter in the filename and would get a fairly good distributed number of files per directory.
One last thing to consider is the possible collision of file names. A user should not be able to guess a filename from another user. So you might need some additional checks here.
Depending on the level of security you want to achieve you can apply more and more patterns.
Just don't save the files in the public folder and create a controller that will send the files.
How you want to organise from that point on is your choice. You could make a sub folder per user. There is no need to rename from a security point of view, but do try to cleanup the filename, spaces and non ascii characters make things harder.
For simple cases (where you don't want to distribute the file store):
Store the files in the tmp directory. DON'T store them in public. Then only expose these files via a route and controller where you do the authentication/authorisation checks.
I don't see any reason to rename the files; you can separate them out into sub directories based on the user ID. But if you want to allow the uploading of files with the same name then you may need to generate a unique hash or something for each file's name.
See above. You can partition them any way you see fit. But I would definitely recommend partitioning them and not lumping them in one directory.
I have .Net desktop app which users can download from my website. I want to customize this app to per user basis.
Is there way to modify exe before downloading, just to change few strings with appropriate for the users downloading ?
Or it is possible to pass command line parameters to this exe via URL ?
The .exe file needs to be customized for it to behave differently for certain downloads.
Skip below to find the solution I found tolerable.
Add section to the .EXE file – Not ideal.
The .exe file has sections one after the other. You could add a section with your data in it, which the executable would then read. This requires you to modify (have access to) the source code of the executable for it to do anything meaningful with the data. Also getting familiar with the .exe file format and modifying it on the web server side as well al playing with it in the program's source code is somewhat tedious.
Change resources section of the .EXE file – Not ideal.
A dedicated "resources" section exists in the executable. You could add custom strings or blob of data to it. Same cons as the first one.
Overwrite data in the .EXE at a fixed position – Passable.
Have the executable read data from itself from a fixed position in the file, which is overwritten with the customization data when serving the .exe file. Requires modifying the executable's source code.
Append data to the .EXE – Passable.
Append data to the executable. Again, reading it and doing anything special with it requires the executable itself doing so.
☑ Wrap the .EXE in another .EXE and append your data to it – Tolerable.
Create a program to which the original executable and the custom data will be appended to. When this custom program is then executed, it will extract the embedded executable and launch it with the custom data as it arguments.
This kind of a bundle-executable is also easy to produce on most server-side (scripting) languages. When the download is requested, the server sends the wrapper-exe, the original exe, the customized data and of course some statically-sized data fields denoting the sizes of both of those data blocks so it can extract them.
Cons: Requires such a wrapper program to be created, unless someone already has.
Related links:
1. Best practices to let my web users download custom .exe from my site using PHP
2. Modifying executable upon download (Like Ninite)
If the application is ClickOnce deployed, passing URL parameters is an option in the ClickOnce options dialog. However, I have not yet used this feature.
EDIT
You might want to change some user settings in your configuration depending on the user that actually runs the application. You could also make sure this is done only once per user by adding an appropriate SettingsNeedUpdate setting you set to true after the initial initialization.
Example:
Add new setting "Option1", "Option2" and "SettingsNeedUpdate" which are user settings. In Main you could add something like:
...
try
{
if (Properties.Settings.Default.SettingsNeedUpdate)
{
Properties.Settings.Default.Option1 = ...;
Properties.Settings.Default.Option2 = ...;
Properties.Settings.Default.SettingsNeedUpdate = false;
Properties.Settings.Default.Save();
}
}
catch (Exception exp)
{
...
}
...
You could write a library which can modify an assembly resources (here string table).
This library could benefit from reflection.
When a user asks for your file, asp.net page could customize the exe (using your library) and send it to client.
Not like that, No.
You could however automatically zip (on your server) your exe with a custom app.config file for each user.
Update
Point your download location to a custom HttpHandler that zips together your exe (using http://www.sharpdevelop.net/OpenSource/SharpZipLib/) with a generated (for the current user) application configuration file ( http://generally.wordpress.com/2007/09/27/using-appconfig-for-user-defined-runtime-parameters/).
The user then unzips the two files (MyApp.exe & MyApp.exe.config) to any location and run MyApp.exe.
This method does not work if you have an installer.
I have a upload text file field, and with it I plan to save the file somewhere and then store the location of the file in a database. However, I want to make sure the file they uploaded is a .txt file, and not, say, an image file. I imagine this happens in the validation step. How does one validate such a thing? Also, how do you get the filename of the uploaded file? I could always just check if it said '.txt' but for future reference knowing how to validate without just the filename would be helpful.
Trying to validate the contents of a file based on the filename extension is opening the door for major hackerdom. It's trivial to change the extension and upload the file.
If you are on a Mac/Linux/Unix-based system the OS "file" command is the standard because it looks inside the file for key bytes that flag file types. http://en.wikipedia.org/wiki/File_(Unix) I'm not sure what's available for Windows, but this might help: Determine file type in Ruby
One way of doing it, the simple way really, would be to pass the file through an image loader, preferably one that handles multiple common formats, and see if it throws an error.
The other way is to manually check the file header for common image format headers. For example, .bmp files start with BM. Other formats have their own specific markings you can use.