Creating an uneditable data file in Java

I am currently writing a program which takes user input and creates rows of a comma delimited .csv file. I am in need of a way to save this data in a way in which users are not able to easily edit this data. It does not need to be super secure, just enough so that it couldn't accidentally be edited. I also need another file (or the same file?) created to then be easily accessible (in the file system) by the user so that they may then email this file to a system admin who can then open the .csv file. I could provide this second person with a conversion program if necessary.

The file I save data in and the file to be sent can be two different files if there are any advantages to this. I was currently considering just using a file with a weird file extension, but saving it as a text file so that the user will only be able to open it if they know to try that. The other option being some sort开发者_如何学Python of encryption, but I'm not sure if this is necessary and even if it was where I would start.

Thanks for the help :)

Edit: This file is meant to store the actual data being entered. Currently the data is being gathered on paper forms which are then sent to the admin to manually enter all of the data. This little app is meant to have someone else enter the data from the paper form and then tell them if they've entered it all correctly. After they've entered it all they then need to send the data to the admin. It would be preferable if the sending was handled automatically, but this app needs to be very simple and low budget and I don't want an internet connection to be a requirement.

You could store your data in a serializable object and save that. It would resist casual editing and be very simple to read and write from your app. This page should get you started: http://java.sun.com/developer/technicalArticles/Programming/serialization/

From your question, I am guessing that the uneditable file's purpose is to store some kind of system config and you don't want it to get messed up easily. From your own suggestions, it seems that even knowing that the file has been edited would help you, since you can then avoid using it. If that is the case, then you can use simple checks, such as save the total number of characters in the line as the first or last comma delimited value. Then, before you use the file, you just run a small validation code on it to verify that the file is indeed unaltered.

Another approach may just be to use a ZIP (file) of a "plain text format" (CSV, XML, other serialization method, etc) and, optionally, utilize a well-known (to you) password.

This approach could be used with other stream/package types: the idea behind using a ZIP (as opposed to an object serializer directly) is so that one can open/inspect/modify said data/file(s) easily without special program support. This may or may not be a benefit and using a password may or may not even be required, see below.

Some advantages of using a ZIP (or CAB):

1. The ability for multiple resources (aids in extensibility)
2. The ability to save the actual data in a "text format" (XML, perhaps)
3. Maintain competitive file-sizes for "common data"
4. Re-use existing tooling support (also get checksum validation for free!)

Additionally, using a non-ZIP file extension will prevent most users from casually associating the file (a similar approach to what is presented in the original post, but subtly different because the ZIP format itself is not "plain text") with the ZIP format and being able to open it. A number of modern Microsoft formats utilize the fact that the file-extension plays an important role and use CAB (and sometimes ZIP) formats as the container format for the document. That is, an ".XSN" or ".WSP" or ".gadget" file can be opened with a tool like 7-zip, but are generally only done so by developers who are "in the know". Also, just consider ".WAR" and ".JAR" files as other examples of this approach, since this is Java we're in.

Traditional ZIP passwords are not secure, and more-so is using a static password embedded in the program. However, if this is just a deterrent (e.g. not for "security") then those issues are not important. Coupled with an "un-associated" file-type/extension, I believe this offers the protection asked for in the question while remaining flexible. It may be possible to entirely drop the password usage and still prevent "accidental modifications" just by using a ZIP (or other) container format, depending upon requirement/desires.

Happy coding.

Can you set file permissions to make it read-only?

Other than doing a binary output file, the file system that Windows runs (I know for sure it works from XP through x64 Windows 7) has a little trick that you can use to hide data from anyone simply perusing through your files:

Append your output and input files with a colon and then an arbitrary value, eg if your filename is "data.csv", make it instead "data.csv:42". Any existing or non-existing file can be appended to to access a whole hidden area (and every file for every value after the colon is distinct, so "data.csv:42" != "data.csv:carrots" != "second.csv:carrots").

If this file doesn't exist, it will be created and initialized to have 0 bytes of data with it. If you open up the file in Notepad you will indeed see that it holds exactly the data it held before writing to the :42 file, no more, no less, but in reality subsequent data read from this "data.csv:42" file will persist. This makes it a perfect place to hide data from any annoying user!

Caveats: If you delete "data.csv", all associated hidden data will be deleted too. Also, there are indeed programs that will find these files, but if your user goes through all that trouble to manually edit some csv file, I say let them.

I also have no idea if this will work on other platforms, I've never thought to try it.