How To Work With Jar Files: Create, Open, Edit
From time to time, I find myself needing to edit the content of a JAR file. As many of you may know, a JAR file is essentially a zipped folder. So every time I need to edit a file within it, I used to follow this process: first, decompress the JAR, then edit the file, and finally, compress it back into a JAR. Let's go one by one and in the end I will show you how to edit a jar file without opening it.
How to create a Jar file
If you have a folder and you want to make a jar out of this folder, you can do this by using jar command:
jar cvf destination.jar source-folder
Here, every file from the source-folder will be added to the destination.jar file with preserved folder structure.
How to extract a Jar file
It could be done by the same jar command:
jar -xf destination.jar
After running this command, files from the jar will be extracted to the same location where jar is located.
However, it turns out that this whole process isn't necessary and can be done more conveniently using the Vim editor in-place.
How to edit a Jar file inplace
All you need to do is type:
vim editme.zip
This will open up the Vim editor, allowing you to navigate through the folder structure(!) and edit the files directly.
How to convert Jar to Zip
As stated before, JAR files are essentially ZIP files with a specific structure for Java applications. You can convert a JAR file to a ZIP file using three different methods:
Simple Rename Method:
The easiest way to convert a JAR file to a ZIP file is to simply rename the file extension.
Steps: a. Locate the JAR file you want to convert. b. Right-click on the file and select "Rename." c. Change the file extension from .jar to .zip. d. Confirm the change if prompted.
Using Command Line:
You can use the command line to convert JAR to ZIP using the 'cp' (copy) command on Unix-like systems or 'copy' on Windows.
For Unix-like systems (Linux, macOS):
cp filename.jar filename.zip
For Windows:
copy filename.jar filename.zip
Using 7-Zip or Similar Archive Tools:
Archive management tools like 7-Zip can be used to convert JAR to ZIP.
Steps: a. Install and open 7-Zip. b. Navigate to the JAR file. c. Right-click on the JAR file. d. Select "7-Zip" > "Add to archive..." e. In the "Archive format" dropdown, select "zip". f. Click "OK" to create the ZIP file.
Remember that while these methods will allow you to access the contents of the JAR file as a ZIP, converting back from ZIP to JAR might not always work perfectly, especially if the original JAR had specific metadata or structure important for Java applications. If you need to modify and reuse the JAR, it's often better to work with it in its original format.
Happy coding!