How to decompile a whole Jar file?

Question

Does anyone know of a free decompiler that can decompile an entire Jar file instead of a single class? I have a problem with sub classes like name$1.class name$2.class name.class

Answer 1

2009: JavaDecompiler can do a good job with a jar: since 0.2.5, All files, in JAR files, are displayed.

See also the question "How do I “decompile” Java class files?".

The JD-Eclipse doesn't seem to have changed since late 2009 though (see Changes).
So its integration with latest Eclipse (3.8, 4.2+) might be problematic.

JD-Core is actively maintained.

Both are the result of the fantastic work of (SO user) Emmanuel Dupuy.

---

2018: A more modern option, mentioned in the comments by David Kennedy Araujo:

JetBrains/intellij-community/plugins/java-decompiler/engine

Fernflower is the first actually working analytical decompiler for Java and probably for a high-level programming language in general.

java -jar fernflower.jar [-<option>=<value>]* [<source>]+ <destination>

java -jar fernflower.jar -hes=0 -hdc=0 c:\Temp\binary\ -e=c:\Java\rt.jar c:\Temp\source\

See also How to decompile to java files intellij idea for a command working with recent IntelliJ IDEA.

Answer 2

First of all, it's worth remembering that all Java archive files (.jar/.war/etc...) are all basically just fancy.zip files, with a few added manifests and metadata.

Second, to tackle this problem I personally use several tools which handle this problem on all levels:

• Jad + Jadclipse while working in IDE for decompiling .class files
• WinRAR, my favorite compression tool natively supports Java archives (again, see first paragraph).
• Beyond Compare, my favorite diff tool, when configured correctly can do on-the-fly comparisons between any archive file, including jars. Well worth a try.

The advantage of all the aforementioned, is that I do not need to hold any other external tool which clutters my work environment. Everything I will ever need from one of those files can be handled inside my IDE or diffed with other files natively.

Answer 3

If you happen to have both a bash shell and jad:

JAR=(your jar file name)
unzip -d $JAR.tmp $JAR
pushd $JAR.tmp
for f in `find . -name '*.class'`; do
    jad -d $(dirname $f) -s java -lnc $f
done
popd

I might be a tiny, tiny bit off with that, but it should work more or less as advertised. You should end up with $JAR.tmp containing your decompiled files.

Answer 4

I have had reasonable success with a tool named (frustratingly) "JD: Java Decompiler".

I have found it better than most decompilers when dealing with classes compiled for Java 5 and higher. Unfortunately, it can still have some hiccups where JAD would normally succeed.

Answer 5

Something like:

jar -xf foo.jar && find . -iname "*.class" | xargs /opt/local/bin/jad -r

maybe?

Answer 6

Insert the following into decompile.jar.sh

# Usage: decompile.jar.sh some.jar [-d]

# clean target folders
function clean_target {
  rm -rf $unjar $src $jad_log
}

# clean all debug stuff
function clean_stuff {
  rm -rf $unjar $jad_log
}

# the main function
function work {
  jar=$1
  unjar=`basename $jar.unjar`
  src=`basename $jar.src`
  jad_log=jad.log

  clean_target

  unzip -q $jar -d $unjar
  jad -d $src -ff -r -lnc -o -s java $unjar/**/*.class > $jad_log 2>&1

  if [ ! $debug ]; then
    clean_stuff
  fi

  if [ -d $src ] 
    then
      echo "$jar has been decompiled to $src"
    else
      echo "Got some problems check output or run in debug mode"
  fi
}

function usage {
  echo "This script extract and decompile JAR file"
  echo "Usage: $0 some.jar [-d]"
  echo "    where: some.jar is the target to decompile"
  echo "    use -d for debug mode"
}

# check params
if [ -n "$1" ]
  then
    if [ "$2" == "-d" ]; then
      debug=true
      set -x
    fi
    work $1
  else
    usage
fi

• chmod +x decomplie.jar.sh //executable
• ln -s ./decomplie.jar.s /usr/bin/dj

Ready to use, just type dj your.jar and you will get your.jar.src folder with sources. Use -d option for debug mode.

Answer 7

You extract it and then use jad against the dir.

Answer 8

Note: This solution only works for Mac and *nix users.

I also tried to find Jad with no luck. My quick solution was to download MacJad that contains jad. Once you downloaded it you can find jad in [where-you-downloaded-macjad]/MacJAD/Contents/Resources/jad.