I have configured vim to automatically decompile ".class" files similar to the instructions in: http://vim.wikia.com/wiki/VimTip54.

I have made a minor change to use cfr_0_115 as below:

augr class
au bufreadpost,filereadpost *.class silent %!java -jar /blah/cfr_0_115.jar %
au bufreadpost,filereadpost *.class set readonly
au bufreadpost,filereadpost *.class set ft=java
au bufreadpost,filereadpost *.class silent normal gg=G
au bufreadpost,filereadpost *.class set nomodified
augr END

This works fine when opening files from the shell.

Sometimes I work with JAR files and would like to achieve the following workflow:

  1. :Explore (and navigate to the JAR file)
  2. View the JAR file and select a Class
  3. When this Class is opened, it should be ran through CFR.

Currently, when I get to step "3" the class is not decompiled for viewing. I'd love to know how I can get the class file from a JAR opened 'through' the class decompiler.

Edit 1 - With Vim logging enabled, when I open a class file that is NOT within a JAR file, I see Executing BufRead Auto commands for "*.class include the command I wish to run. However, when I open the class file from within a jar, I do not see the command in the logs.

Edit 2 - Relevant log entries when opening a JAR:

Executing BufReadCmd Auto commands for "zipfile:*/*"
autocommand call zip#Read(expand("<amatch>"), 1)

Calling shell to execute: "(unzip -p -- '/blah/original-httpclienttest-1.0.jar' 'com/atlassianlabs/sslclient/Main.class') >/var/folders/ys/18xytj217f749_vx7rhs4t7w0000gp/T/vwqRYKe/1 2>&1"
fchdir() to previous dir
Reading viminfo file "/blah/.viminfo" marks

and later:

Executing BufRead Auto commands for "*.class"
autocommand setf stata

However when I open a class file by navigating to it directly with the file explore (:Explore) I see:

Executing BufRead Auto commands for "*.class"
autocommand silent %!java -jar /blah/cfr_0_115.jar


I don't know why the autocmd's that exist are not getting picked up when opening from a JAR, because VIM is actually running some autocmd, just not the one I want and "autocommand setf stata" is not even present when opening a class. I'm blocked in terms of how to debug this further.

More Follow-up

I got this working to some extent by adding a function to the filetype.vim file on class files. However, vim reports the file name in the format: ZIPFILEPATH::PATHTOCLASS in the JAR.. I was hoping it would send though the temp file path instead.

  • 1
    I don't know why the autocommand doesn't trigger when you open the file from a JAR but a workaround could be to put in your vimrc a function which will execute your list of commands, bind a key to call the function and use it to manually decompile the file.
    – statox
    May 11, 2016 at 7:25
  • 3
    How are you looking within the JAR? 7-zip or something? I'm not sure but I'm guessing that the fact that the file is compressed is messing with vim.
    – Tumbler41
    May 11, 2016 at 13:23

1 Answer 1


By starting vim using: vim -V9aLogFile.log I was able to determine that when :Explore opens a file, it checks the content of filetype.vim and autocmd's are working from there.

Because vim reports the filename of a class inside a jar file in the format zipfile::path-to-jar::path-to-class I needed to workaround that as my Java decompiler couldn't handle this type of file path.

I created a shell "wrapper" script:



fileType=$(echo $* | cut -f1 -d:)
jarFile=$(echo $* | cut -f2 -d:) 
classFile=$(echo $* | cut -f4 -d:) 

if [ $fileType = "zipfile" ]
    unzip -qq $jarFile $classFile -d $tmpDir 
    java -jar $pathToDecompiler $tmpDir/$classFile
    rm -rf /tmp/$uuid/ >&/dev/null
    java -jar $pathToDecompiler $*

The above script handles two cases, when opening a normal class file, and when opening a class file from the Explore Command, it creates a file in temp. Note: when writing this, I found entering rm -rf ... particularly scary in the event a variable didn't get populated. I decided to play it safe and hard-code '/tmp'.

Then I created a function back in the filetype.vim file:

" Java Class
au BufRead *.class call SetClassOptions()
function SetClassOptions()
     setf stata
     silent %!/blah/get-class-from-jar.sh %
     set readonly
     set ft=java
     silent normal gg=G
     set nomodified

It's a little hacky, and I am sure it could be polished or completed in a more 'vim' way, but at least it has my usecase sorted.

final result is recorded: https://giphy.com/gifs/l41Yf8WlUQWj3R6hy

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