Develop Reference

Storing data in text files with Java/Maven

I wrote a little Java app for analyzing .csv files. Now I want to keep reading from and writing to a .txt file, which acts similar to a mini-database. For this purpose I simply added the .txt in my project and used the Files.readString(Path) and Files.write(Path path, byte[] bytes) methods.
When I do this in IntelliJ I have no problems but as soon as I build/export the file with Maven and started with the created launcher the app didn't work because the project structure / file organization isn't the same anymore.
I also tried to just add the .txt file to the exported folder afterwards but even then I couldn't manage to implement a relative path to the file.
I'm still relatively new to programming and it's just a small app so I don't think mySQL would fit my needs. I've also read that I could store the data in a property file but I don't know if that would be the right way to archive what I want. Certainly it must be possible to somehow keep a .txt for reading and writing in your exported project. Does someone have an idea?

If you use a ´*.txt` file for storing, that file cannot be inside the jar because the jar cannot change its contents while running.
You need to put the file somewhere else, either at some dedicated location (let the user choose/configure one), or next to the jar. To figure out your own execution path, you can use
How to get the path of a running JAR file?

Maven is one tricky tool. You need to go to the pom file and add the resource.
Unable to add resources to final jar for maven project in Intellij.
-I hope this helps
Trader

IntelliJ IDEA - Decompiling/Editing/Recompiling JAR

I realize this may seem like a completely stupid question and this question is a "wall of text", but I'm feeling like I've gotten way out of my depth here and need some guidance. I've read several SO questions on this topic, but still can't seem to find one that addresses this particular situation. (please reference update(s) at the end of this post)
BACKGROUND
Our company has an application that was built in Java and released as an executable JAR package by a developer who passed away a couple of years ago. Since then, there has been minimal need for even looking at that code, let alone making any changes. That's been really good because I do my programming in VB.NET (Visual Studio) and, while I can read and make sense of Java code, I'm not proficient in actually writing/debugging that code.
However, a recent issue has come up that forced me to try to take a look at this Java code due to some internal changes in organization and data structure. I've looked in his "src\" directory and found older versions of his original code but wasn't able to find the most recent version anywhere. I found some code that made it possible for me to extract the JAR that's currently being used to a local directory on CodeProject (JarsVB), so I've been able to look over some of the .java files when trying to figure out what query is being used for some random operation. I don't know what tool(s) the original developer used to create the project/JAR, so I've installed the IntelliJ IDEA Community Edition 2018 as an IDE, and it's worked for me so far to simply view the code so I can understand a bit about what it's doing.
PROBLEM/GOALS
Unfortunately, now there is a need for me to make a change to the Java code and update the JAR, and this is where I can't seem to make heads or tails of what I need to do. I have my local copy of the code from the "unzipped" JAR containing all the .java and .class files (along with all the other resources), but I'm not sure how to go from that to modifying the code and recompiling the executable JAR.
So, my goals here are as follows:
(properly) Decompile the existing executable JAR. (If the JarsVB solution I mentioned above did what it was supposed to do, I should already have this part handled, but if there's a better, more "integrated" way of doing it, I'd be open to that as well.)
Modify one or more .java files. (I believe I can figure out the syntax well enough to get this part done.)
Debug/test my changes.
Recompile the changes into an updated executable JAR for release. (THIS is where I'm experiencing the most confusion.)
WHAT I'VE DONE
I've been looking at the documentation for IntelliJ to try to figure out how to make this all happen, but I feel like I'm missing stuff. I set my "Project Structure" settings to point to a specific folder, but I can't seem to get it to actually build anything in my specified path.
I went into one of the .java files and made/saved a small change to test, then went to the Build menu and tried all the building options available to me: "Build Project", "Build Module", and "Rebuild Project". Each time, the event log shows that "All files are up-to-date" (even though I changed one), so I go to my output directory to see what it built, but the folder is empty.
I looked at the IntelliJ documentation for Packaging a Module into a JAR File, which says to
On the main menu, choose Build | Build Artifact
But that option is disabled in my Build menu, and when I look in the Project Structure dialog, the Artifacts section is empty, so I try to add a new setting (Add -> JAR -> From modules with dependencies...), but I'm not sure how to properly set that up either.
I tried to select a Main Class from my classes/ directory, but it wouldn't actually accept any of the .class files I selected, so I just left it blank. Then, I did a search for a MANIFEST file, but couldn't find one anywhere so I left that blank as well. The Build menu option is enabled now, but when I tried to Build Artifact, again, I get nothing in my output directory. In fact, the only files I can find that have changed are in my local working directory. I'm just dumbfounded at this point.
FINAL THOUGHTS/QUESTIONS
I've tried to provide as much detail here as I could think of about all the things I've tried and gone through to get this JAR updated, but if there's a question about anything, please let me know. I'm not looking for a "handout" and I don't expect anyone to do this for me, but I'm also not wanting to become a Java developer just for the sake of making some minor changes to an application that will eventually be replaced by a .NET application. I simply am not familiar enough with the tools or Java development in general to know how to get to where I want to be from where I am.
My decompiled source files are in a totally separate directory from the original, production JAR file because, when I recompile this time, I want to completely recreate the JAR. Am I understanding the Java development process correctly in editing one of the .java files I got from decompiling with the JarsVB and then recompiling the JAR?
Thanks in advance for any assistance in finding the resources I need to accomplish these goals.
EDIT/UPDATE
So, looking at the link in the accepted answer in another SO question, How to build jars from IntelliJ properly?, I figured out at least one part of my issue: Leaving the Main Class setting of my Artifacts configuration blank was a problem. Since I hadn't been able to select a .class file and I wasn't sure how to correctly populate that field, I hadn't given the IDE enough information to operate correctly. I entered the namespace and class (namespace.class) I found in the class file that apparently defines the main method for the application, then set the path for the MANIFISET.MF file to my output directory and tried again to Build Artifact.
This time, at least, it DID produce a JAR in my defined output directory, but it's only 1KB in size. As stated above, the source files are in a completely separate directory from the original JAR file from which they were decompiled. The output directory, too, is completely separate from the location of the original JAR file. Do I need a copy of the original JAR file in the output path for recompiling to work correctly?
I'm making progress, but I'm sure I'm overlooking something "stupid" at this point that's primarily due to my unfamiliarity with the IDE and developing Java applications in general.
UPDATE 2
Looking at another SO question - how to create jar of java package in intelliJ idea - I learned that I have to individually add the necessary files for repackaging into the JAR. However, this brings up the question, what files do I add? The linked question identifies the .class files, but when I go look at the .class files in my working directory, none of those have been updated recently, so it looks like I'm still missing a step somewhere.
Another question this brings up is, are there certain conventions for Java development of which I need to be aware when preparing my environment? I have my output path set to a completely separate folder than any working or production code, so I'm wondering if something in that setup might potentially cause issues.
As I said before, I made a small change to one of the .java files, then tried both the Build Module and Rebuild Project options, but those are still telling me that "All files are up-to-date". Even so, I tried adding just the .class files from under my classes\ directory to my Artifact configuration and tried again to Build Artifact. I got a bit larger file (approx. 5MB), but when I try to execute the JAR, it just doesn't appear to do anything, let alone actually launch the application.
I tried again by adding the root folder of my local copy of the source adding everything the root folder contains. (yes, the directory probably needs some "spring cleaning", but that's for another day)
This time, I got a much larger file this time (approx. 21MB), so I thought I might have fixed the problem. Unfortunately, no such luck. The JAR still doesn't appear to execute.
For reference, the original JAR file from which the code was decompiled is approx. 59MB in size so, either IntelliJ is doing an incredible job with compression, or there's yet another step I haven't yet found. I'm sure this is all a matter of getting my IDE configured correctly, but I just can't seem to find the right combination of settings.

How do I import an external jar file and a separate file as a command line argument in Netbeans?

I'm having difficulty with my latest programming project. I have a program in Netbeans which relies upon an external library contained within a jar file. I am expected to use several imports to get the operations I need. While that's all fine and dandy, it also means I can't debug this code to make sure it works. I did see something on StackOverflow about doing a copy-pasta on the jar file into my code, but it uses so many commands and so much code that it would be more helpful to import the whole jar file, if possible.
How do I get Netbeans to recognize that I have an external jar file somewhere that it needs to read from in order to get its information?
Furthermore, I am expected to read in a file via the args[], and I am not sure how to read in command line arguments in Netbeans. How do I do this, and where am I expected to put the file to be read in?

I have figured out my issues and am going to answer this for future reference to anybody with this exact same problem. When you have a NetBeans project, you can open the project hierarchy and get a list of your source packages, test packages, libraries, and test libraries. The Libraries folder is where I needed the jar file.
I can right click on the libraries tab to add a jar/folder. Doing so gave me a file explorer to navigate to where I had my jar saved, and adding it fixed all the warnings for external library imports. The program now knows where to look for all the external libraries. Presumably, I'd have to repeat this if I ever moved the jar file.
As for adding the arguments, I found this under Run>Set Project Configuration>Customize. This brings up a window with the project properties. One of the text boxes will be for "Arguments," and filling this in with your commands will give you those commands as your Args[].

What's the best way of storing and extracting files inside the .jar archive?

I am looking for a way to store files inside the jar (and extract them), but it must work when running/debugging from Eclipse as well.
explanation:
Storing files as in images that I want to use for an icon of a Frame. I hope it's clear now.

I still think that the question is a bit unclear.
What is it that you want to do? You can create and read from jar-files using JarInputStream/JarOutputStream, and you can also read files from jar-files that are on the classpath using Class.getResourceAsStream(String name)

I don not get your question clearly.
Eclipse can export runnable jar files , right click on the project name and choose export. Then from the dialog choose runnable jar file under java category.

Creating JAR file using Eclipse IDE is pretty much easy.
Follow the simple steps.
1. Right click on your project, which you want to create a JAR file.
2. Select Export from the context menu.

Eclipse understands Ant build files. Write a build file that (compiles &) Jar's the code at the same time and this becomes a non-issue.

Exporting Images with JAR in Eclipse (Java)

I've been working on a little project that requires external images for display. I'm not all that familiar with how to use Eclipse and this is my first time attempting to export a completed project so I can share it with others. Right now, it seems the only way I can get my images to show up is if I assign a specific folder on my hard drive and have the image paths in the code go to that.
I'm looking for a way to export the images as part of my JAR or as part of the same package so when I go to send this program to other people, I don't have to send them a separate archived folder of images. I'd also be interested in learning what I need to do to have my code reference the images within that package so they'll work without an external folder.
I have read about some kind of package system within Eclipse, but have thus far had no luck in figuring out how to use it. Could use some explicating!
Thanks in advance to anyone willing to give me their two cents.

Something I would have found useful with this answer is the following: make sure you put your images/files in the same eclipse folder (or sub-folder below) as your source code. I created a folder "images_ignored" using eclipse, added it to the build path but still it refused to be included in my JAR file (when creating an executable JAR).

Just drag the images folder into your Eclipse project, then choose to "Copy New Folder" or "Copy File and Folder" depending on Eclipse version, and then right click on the image folder (in Eclipse) and --> build path "use as source folder".

you might need to load them as class path resources if they are within a jar. see: getClass().getClassLoader().getResourceAsStream(...)

Use getResource() to load the images:
ImageIcon qmarkIcon = new ImageIcon(getClass().getResource("images/mark.gif"));

If you're using JDK 1.7 or JDK 1.8, you might want to use the NIO.2 API.
for (FileSystemProvider provider : FileSystemProvider.installedProviders()) {
if ("jar".equals(provider.getScheme()))
return provider.newFileSystem((new File(Start.class
.getProtectionDomain().getCodeSource().getLocation().toURI()))
.toPath(), new HashMap<String, Object>());
}
If you enter this code into a method that returns a java.nio.file.FileSystem, you can call the method to get the FileSystem for the JAR file.
To get the path to access the files inside your JAR file, you can use the following method, which then allows you to read the files however you may want.
fileSystem.getPath("/images/image.gif")
If you would like to be able to run this in Eclipse, make sure you surround the call to the method with a try/catch IOException and assign to your FileSystem object the following.
new File(Start.class.getProtectionDomain().getCodeSource().getLocation().toURI())
.toPath().toString();
This will allow you to run your program whether it's compressed into a JAR file or not.
I recommend you get used to using NIO.2, since it is a very powerful API.

If you add a folder to build path you can retrieve the images either in eclipse and when you exported it in jar file, just remember to don't reference the image with the path like img/myImage.gif but only myImage.gif !