I am trying to create a java standalone program and was wondering if there is a way to have some sort of data storage within my jar?
You see, my initial idea was to use xml files within the jar for reading and writing stuff in. I had no problem reading stuff from the xml files but I was told you cant really edit/create new files within a jar.
I want it so when i send the executable jar to my friend, initial data I have put in will be in it already and then they can just add to or change the data. I find it pretty tricky as it has to be a form of data storage without the internet access or any need for my friend to install anything more.
I decided to go for sqlite in the end. It works exactly how i want it to work. I might look into javaDB in the future as it seems to have better SQL language support sqlite.org/cvstrac/wiki?p=SqliteVersusDerby
As far as I know, JAR files are read-only, which cannot be rewritten to.
My suggestion is to use MS Access database as your JAR's data keeper.
As it is portable, the only weakness is that you have to bring both of your JAR and MDB files together (or put them in 1 folder).
Related
I need to load "configuration" type files for my program in Android, they are both .bin files containing dictionary data for the NLP library. I'm a bit new to Android still, and I'm having trouble finding a folder to place the files in so I can access them when the activity starts.
I also need to create/save/load a filetype specific to my program, and I don't know where to put it either. All I've been able to find on here is people using the getAssetManager() function to fetch input streams, but I explicitly need File objects for me to be able to load them into my pre-existing desktop software code I'd like to reuse (plus the libraries require them anyway)
I've also seen people using a "res/raw" folder, however the ADT did not generate this "raw" file when I made the project - so I'm not sure what to do there either.
Here is how I usually start the software in the desktop version, but I need to fetch these files in an Android environment:
brain.start(new File("memboric.core"), new File("en_pos_maxent.bin"), new File("en_sent.bin"));
core = brain.getInterpreter().getCore();
The memboric.core file can be generated, but I need to know WHERE and HOW to do so.
Thank you very much for your time, feel free to direct me to other resources if you feel this question is inadequate.
TLDR; how do I load "static" files for the software to function (needs to be included with software), and how to create/load/save "personal" files into an appropriate area of the device?
Use Context.getFilesDir(). Your application can read and write files in that folder and they'll automatically get deleted if your application gets uninstalled.
From that point forward, you can create, delete and read from files like any other Java application.
the "raw"-folder you can create it on your own. So check this out, which shows how to handle files in Android: http://developer.android.com/training/basics/data-storage/files.html
I have a small java utility application which performs tasks on remote computers. This app will provide user with a dropdown/combobox where they can enter ip address or hostnames for the computers they wish to connect to. It would be nice if the users could have a history of items/hosts they had connected in the dropdown.
I thought that I can create a file inside the distributable jar and use it to maintain the history. But writing to a file inside the jar seems to be impossible? The alternate approaches would be to use text files, databases etc located outside the jar. But this is not quite I would like to do as my utility app is only one file and I would like it to be completely independent of any external files. Also its not nice to have a text file stick around your jar file or create a text file each time your app is run.
Considering this case what options can I use? Are there any apis that can help in storing or keeping history?
Why don't you store this info with an hidden file in the user home directory? Many application do the same thing.
You can get the user home directory in this way
String userhome = System.getProperty("user.home");
I'd recommend keeping some .dat file somewhere associated with the JAR. Could be in same directory, or in the user's home (as #dash1e recommends) to avoid any permissions issues. I think you'll find that's the simplest solution.
Another option would be to use a Java-based database solution which could be bundled into your JAR (see Apache Derby, et al). Note that this would create files somewhere, but you wouldn't have to worry about the file-level management, as you'd just be interacting with it as a database.
One final option, if you really insist on avoiding having to maintain your own file, would be to use the Java Preferences API which provides an OS-agnostic way of storing data on the system in some obfuscated location. This is arguably a bit of a misuse of the goal of this API, but would accomplish what you're asking for.
Is there any way in Java to store external files (inside jar) safely? Java files are compiled to .class files and not readable.
I'm planning to use this meganism to store sql files, which hold queries, however i dont want those to be readable when one extracts the jar. External files are pre, cause we then have syntax highlighting while developping instead of putting them into a string.
A jar file is pretty much just a .zip file, so you can put whatever you want in them. There's no built-in encryption, so if you're trying to make the SQL files non-readable, you'll have to encrypt them (and then unencrypt in your code). I don't understand what you mean by "External files are pre, cause we then have syntax highlighting while developping instead of putting them into a string."
Yes, people do this all the time. Just add the files to the jar, and then access them with
getResourceAsStream. If you build with maven, you just plop them into src/main/resources to get them into the jar.
Of course you can put them in the Jar. Once there you can get at them by using the ClassLoader's getResourceAsStream method.
The challenge is to prevent other people extracting them. If your code can read them, so can someone else. What are your requirements here?
I am developing a small game in Java and I am shipping it as a single Jar file. I want to store the high scores/best times for that game somewhere. Instead of storing it in a separate file, I would like to store it in the application itself (inside the Jar) so that its not lost. Is this possible at all ? If so, how to do it programatically.
Java does not give you tools to modify the JARs which are currently run. If you really want to do it, you have to guess the location of the JAR by yourself (which might reside on a read-only filesystem) and modify it the same way you would modify any archive file.
Bottom line: it's a very bad idea, don't do it! See this question for a much more reasonable solution.
Nothing is impossible, but storing it in the jar file would make it very complicated. You might also end up with unwanted side effects like "Permission Denied" errors when the jar is owned by another user. Virus scanners might get nervous when they see jar files change without reason, etc....
I would look to the Preferences API for storing this kind of info.
I think it is a bad idea to try and store anything in the jar file. Another option is to have a web based service offered to the people playing with your game. The game could connect through a web service to your hosted server and then store everything centrally there. Not sure if it is exactly what you want but it's just an idea. It would also allow people to compete with each other.
Java JAR file is a ZIP-Archive, so you could possibly access it with standard ZIP-Tools and just extract one hisghscores.txt file, modify it and then pack it back again.
I've only just started to write in Java on Android, so please bear with me.
I have some settings I want to hold in my app, normally I would have used an xml file. Trouble is i'm not sure how to load it into the xml parser to read it.
I thought I might be able to drop it into /res/values/Info.xml and open it from there but it does'nt find the file.
I have also read that people are starting to use a SQLite database to hold information in, is this more the standard way to go?
thanks a lot
Luke
It sounds like what you want are Shared Preferences. Its a simple way of storing key value pairs, along with a UI for letting the user change them.
You could try storing to External Files (that way they can save settings on an SD card if they have 2.2). You wouldn't be able to modify the files in the res folder like you tried because these files get compiled into the app package. You could also try Internal Files found on the same page. SQLite might be a bit much for config settings.