I was trying to create a .jar from a .java file for a school project but now I can't read my .java file. The code I had written was overwritten somehow and I need to know how to (if possible) revert my .jar file back to the code I had written. Thanks in advance because this is a time sensitive matter.
You could try "decompiling" your JAR file using any JAR decompiler, such as http://www.javadecompilers.com/.
You won't get exactly the source code you originally wrote, but the decompiler will do it's best to map the .class files embedded in the JAR back to Java source code.
If you are using Eclipse you can right click on your project and check in history for getting old code
I have a Java GUI project in netbeans and I want to make Processing Development Environment (PDE) file of it. I have searched everywhere but couldn't find the solution. Please help.
A .pde file is really just a text file with a .pde extension. You can prove this by opening up a .pde file in a basic text editor like notepad or JEdit.
So to create a .pde file, you just have to print some Processing code to a text file and give it a name that ends with .pde.
If you have file associations set up (which happens automatically when you install Processing), then the Processing editor will open .pde files be default.
The Processing editor expects .pde files to be in a folder with the same name as the .pde file, but I think it will actually detect this and move it for you, so that might not be strictly necessary.
Edit: But I wonder if that's what you're actually asking. If what you're actually asking is how to use Processing as a Java library in Netbeans, then that's a different question.
If that is what you're asking, then you're no longer using a .pde file. Instead, you'll need to create a Java project, then add the Processing library jars (located in the Processing directory) to your classpath. After that you can call Processing from Java, and most projects will start with a class that extends PApplet. That class contains your sketch code, and you launch it by calling PApplet.main("YourSketchNameHere"); from the regular main() method.
I have made a small program in Java that displays its .java source with a gui. It does not use FileChooser to do this. I am reading the .java sources with the aid of following statements
String resName = "/dev/classes/"+name+".java"
Scanner s = new Scanner(FilePrinter.class.getResourceAsStream(resName));
where name is the name of the .java file i.e. if the file is MyProg.java then name==Myprog. Of course my program is inside the dev.classes package
The thing is that when I export my project to JAR and include source files this works because source files reside inside the /dev/classes/ directory.
However, I haven't yet discovered a way to make my program run in Eclipse or from the command line without giving me exception.
And of course when someone tries to add those source files to be used automatically as resource files the process fails.
Can I somehow use the same code both when running from Eclipse and from the JAR? It must be something very trivial but because I am not Java expert I cannot see.
I found how to do it. Actually you either have to use Ant or Maven. However, this can be done in Eclipse as well as follows:
On the Eclipse Project Properties>Java Build Path you can choose on the bottom Default Output folder: <your_project_name>/src.
This causes class files be compiled in the same directory as the .java files and finally does what I wanted.
Thanks to #AndrewThompson for suggesting to try this
I'm trying to view a java class file in Notepad++ or Notepad, it was in a .jar file and I unzipped it, and it has characters like NUL and DC1 and DC2 and SOH and other "gibberish" looking characters...is there a way to fix/avoid this?
Class files are binary files compiled from source code. They're not supposed to be human readable. You want to find the .java source files used to create them if you want to read the code.
Or use a Java decompiler to revert the class files back into source code.
Class files are binary, not text. They're not supposed to look correct in a text editor.
I would like to modify a file inside my jar. Is it possible to do this without extracting and re jarring, from within my application?
File i want to modify are configuration files, mostly xml based.
The reason i am interested in not un jarring is that the application is wrapped with launch4j if i unjar it i can't create the .exe file again.
You can use the u option for jar
From the Java Tutorials:
jar uf jar-file input-file(s)
"Any files already in the archive having the same pathname as a file being added will be overwritten."
See Updating a JAR File.
Much better than making the whole jar all over again. Invoking this from within your program sounds possible too. Try Running Command Line in Java
You can use Vim:
vim my.jar
Vim is able to edit compressed text files, given you have unzip in your environment.
Java jar files are the same format as zip files - so if you have a zip file utility that would let you modify an archive, you have your foot in the door. Second problem is, if you want to recompile a class or something, you probably will just have to re-build the jar; but a text file or something (xml, for instance) should be easily enough modified.
As many have said, you can't change a file in a JAR without recanning the JAR. It's even worse with Launch4J, you have to rebuild the EXE once you change the JAR. So don't go this route.
It's generally bad idea to put configuration files in the JAR. Here is my suggestion. Search for your configuration file in some pre-determined locations (like home directory, \Program Files\ etc). If you find a configuration file, use it. Otherwise, use the one in the JAR as fallback. If you do this, you just need to write the configuration file in the pre-determined location and the program will pick it up.
Another benefit of this approach is that the modified configuration file doesn't get overwritten if you upgrade your software.
Not sure if this help, but you can edit without extracting:
Open the jar file from vi editor
Select the file you want to edit from the list
Press enter to open the file do the changers and save it
pretty simple
Check the blog post for more details
http://vinurip.blogspot.com/2015/04/how-to-edit-contents-of-jar-file-on-mac.html
I have similar issue where I need to modify/update a xml file inside a jar file.
The jar file is created by a Spring-boot application and the location of the file is BOOT-INF/classes/properties
I was referring this document and trying to replace/update the file with this command:
jar uf myapp.jar BOOT-INF/classes/properties/test.xml
But with this, it wont change the file at the given location. I tried all the options also but wont work.
Note: The command I am executing from the location where jar file is present.
The solution I found is:
From the current location of jar file, I created folders BOOT-INF/classes/properties
Copy the test.xml file into the location BOOT-INF/classes/properties.
Run the same command again. jar uf myapp.jar BOOT-INF/classes/properties/test.xml
The xml file has been changed in the jar file.
Basically you need to create a folder structure like where the file is located into the jar file. Copy the file at that location and then execute the command.
The problem with the documentation is that, it does not have enough examples as well as explanation around common scenarios.
This may be more work than you're looking to deal with in the short term, but I suspect in the long term it would be very beneficial for you to look into using Ant (or Maven, or even Bazel) instead of building jar's manually. That way you can just click on the ant file (if you use Eclipse) and rebuild the jar.
Alternatively, you may want to actually not have these config files in the jar at all - if you're expecting to need to replace these files regularly, or if it's supposed to be distributed to multiple parties, the config file should not be part of the jar at all.
To expand on what dfa said, the reason is because the jar file is set up like a zip file. If you want to modify the file, you must read out all of the entries, modify the one you want to change, and then write the entries back into the jar file. I have had to do this before, and that was the only way I could find to do it.
EDIT
Note that this is using the internal to Java jar file editors, which are file streams. I am sure there is a way to do it, you could read the entire jar into memory, modify everything, then write back out to a file stream. That is what I believe utilities like 7-Zip and others are doing, as I believe the ToC of a zip header has to be defined at write time. However, I could be wrong.
Yes you can, using SQLite you can read from or write to a database from within the jar file, so that you won't have to extract and then re jar it, follow my post http://shoaibinamdar.in/blog/?p=313
using the syntax "jdbc:sqlite::resource:" you would be able to read and write to a database from within the jar file
Check out TrueZip.
It does exactly what you want (to edit files inline inside a jar file), through a virtual file system API. It also supports nested archives (jar inside a jar) as well.
Extract jar file for ex. with winrar and use CAVAJ:
Cavaj Java Decompiler is a graphical freeware utility that reconstructs Java source code from CLASS files.
here is video tutorial if you need:
https://www.youtube.com/watch?v=ByLUeem7680
The simplest way I've found to do this in Windows is with WinRAR:
Right-click on the file and choose "Open with WinRAR" from the context menu.
Navigate to the file to be edited and double-click on it to open it in the default editor.
After making the changes, save and exit the editor.
A dialogue will then appear asking if you wish to update the file in the archive - choose "Yes" and the JAR will be updated.
most of the answers above saying you can't do it for class file.
Even if you want to update class file you can do that also.
All you need to do is that drag and drop the class file from your workspace in the jar.
In case you want to verify your changes in class file , you can do it using a decompiler like jd-gui.
As long as this file isn't .class, i.e. resource file or manifest file - you can.