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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

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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

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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

User · Answer

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

User · Answer

You can use Vim   vim my jar  Vim is able to edit compressed text files  given you have unzip in your environment

User · Answer

As long as this file isn t  class  i e  resource file or manifest file - you can

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

[java] Modifying a file inside a jar

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