Modifying a file inside a jar

Question

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.

i would like to keep the supplementary files within the application without creating temp files on the file system. — Hamza Yerlikaya, Aug 03 '09 at 22:02
Try this solution http://stackoverflow.com/a/4837522/1853864 I used and my problems were solved. — A. Magalhães, Nov 28 '12 at 12:22
Could you please unaccept the current accepted answer ? It has a negative score and is absolutely not helpful — Dici, Aug 06 '16 at 15:15

score 103 · Accepted Answer · edited May 23 '17 at 11:47

103

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

edited May 23 '17 at 11:47

Community

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answered Aug 18 '13 at 19:52

clwhisk

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Awesome! But they added the pathnames funny. IE Bitbucket.foo.bar instead of the com.etc.etc the existing one has – StarWind0 Jul 03 '16 at 01:50
it says `no such file or directory`. – LoukasPap Jun 16 '23 at 10:22

score 40 · Answer 2 · answered Sep 02 '15 at 12:41

40

You can use Vim:

vim my.jar

Vim is able to edit compressed text files, given you have unzip in your environment.

answered Sep 02 '15 at 12:41

Jose Alban

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This is great. Navigate to the file you're looking for and press Enter. Edit file, then type :wq to save! – Michael Butler May 11 '16 at 15:50
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Also you need `zip` in your environment, to be able to save the changes. Thanks for the answer! – troig Dec 04 '18 at 18:52

score 11 · Answer 3 · answered Aug 03 '09 at 22:03

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.

score 10 · Answer 4 · answered Aug 04 '09 at 01:04

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.

score 5 · Answer 5 · edited Feb 23 '17 at 06:02

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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

edited Feb 23 '17 at 06:02

Neithan Max

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answered Apr 18 '15 at 05:27

Buvin Perera

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score 5 · Answer 6 · answered May 13 '21 at 14:30

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.

dimo414 · Answer 7 · 2015-05-12T03:52:40.527

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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.

edited May 12 '15 at 03:52

answered Aug 03 '09 at 22:12

dimo414

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Agreed. However, you might want to put a "default" configuration file in the JAR, so if something happens to the external one (corrupted, deleted, etc), you can fall back to a default configuration. – Thomas Owens Aug 03 '09 at 22:16
True - though I don't know how many applications would continue to function without their configuration files... – dimo414 Aug 03 '09 at 23:30

score 1 · Answer 8 · answered Apr 25 '12 at 18:19

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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.

answered Apr 25 '12 at 18:19

GreenGiant

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link is broken unfortunately :( – Daniel Barnes Aug 29 '22 at 06:05
For posterity - TrueZip apparently hasn't been maintained since 2012! – GreenGiant Sep 06 '22 at 18:08
Thanks GreenGiant for the update. I used 7zip and that did the task just fine. Just need to edit/modify the existing jar (zip archive) file rather than and renaming – Daniel Barnes Sep 07 '22 at 22:44

aperkins · Answer 9 · 2009-08-03T22:27:28.190

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.

Tomasz Mularczyk · Answer 10 · 2015-03-25T13:46:07.947

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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

edited Mar 25 '15 at 13:46

answered Mar 25 '15 at 12:00

Tomasz Mularczyk

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well, "Use CAVAJ" software is the answer here. The link is just addition if any extra explaining is needed. – Tomasz Mularczyk Mar 25 '15 at 13:37

shoaib · Answer 11 · 2011-08-25T16:15:28.520

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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

edited Aug 25 '11 at 16:15

answered Aug 25 '11 at 04:28

shoaib

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Hi, welcome to stackoverflow. I've removed the abbreviations from your post. In general text message style shorthand isn't appropriate here. I think this answer would be a good answer to the question if you included some more of the details from your blog, within the answer itself so that someone reading your answer learns something even if they don't read the blog, or it gets moved to another URL at some future date. – Flexo Aug 25 '11 at 11:28

score 0 · Answer 12 · answered Jan 18 '17 at 09:36

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.

score 0 · Answer 13 · answered Oct 14 '20 at 08:13

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.

score -1 · Answer 14 · answered Aug 03 '09 at 22:00

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As long as this file isn't .class, i.e. resource file or manifest file - you can.

answered Aug 03 '09 at 22:00

Sorantis

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and how, without extracting and re-jarring? – user85421 Aug 25 '11 at 11:42

Modifying a file inside a jar

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