Comparing two .jar files

Question

How do I compare two .jar files? Both of them have compiled .class files.

I want the difference in terms of method changes, etc.

Answer 1

• JAPICC, sample usage:

  japi-compliance-checker OLD.jar NEW.jar

  Sample reports for log4j: http://abi-laboratory.pro/java/tracker/timeline/log4j/

  

• PkgDiff, sample usage:

  pkgdiff OLD.jar NEW.jar

  See sample report for args4j.

  

• Clirr, sample usage:

  java -jar clirr-core-0.6-uber.jar -o OLD.jar -n NEW.jar

Answer 2

1. Rename .jar to .zip
2. Extract
3. Decompile class files with jad
4. Recursive diff

Answer 3

If you select two files in IntellijIdea and press Ctrl + Dthen it will show you the diff. I use Ultimate and don't know if it will work with Community edition.

Answer 4

I use to ZipDiff lib (have both Java and ant API).

Answer 5

Extract each jar to it's own directory using the jar command with parameters xvf. i.e. jar xvf myjar.jar for each jar.

Then, use the UNIX command diff to compare the two directories. This will show the differences in the directories. You can use diff -r dir1 dir2 two recurse and show the differences in text files in each directory(.xml, .properties, etc).

This will also show if binary class files differ. To actually compare the class files you will have to decompile them as noted by others.

Answer 6

In Linux/CygWin a handy script I use at times is:

#Extract the jar (war or ear)
cd dir1
jar xvf jar-file1
for i in `ls *.class`
do
 javap $i > ${i}.txt #list the functions/variables etc
done

cd dir2
jar xvf jar-file2
for i in `ls *.class`
do
 javap $i > ${i}.txt #list the functions/variables etc
done

diff -r dir1 dir2 #diff recursively

Answer 7

Here is my script to do the process described by sje397:

    #!/bin/sh

    # Needed if running on Windows
    FIND="/usr/bin/find"
    DIFF="diff -r"

    # Extract the jar (war or ear)
    JAR_FILE1=$1
    JAR_FILE2=$2

    JAR_DIR=${PWD}          # to assign to a variable
    TEMP_DIR=$(mktemp -d)

    echo "Extracting jars in $TEMP_DIR"

    EXT_DIR1="${TEMP_DIR}/${JAR_FILE1%.*}"
    EXT_DIR2="${TEMP_DIR}/${JAR_FILE2%.*}"

    mkdir ${EXT_DIR1}
    cd ${EXT_DIR1}
    jar xf ${JAR_DIR}/${JAR_FILE1}
    jad -d . -o -t2 -safe -space -b -ff -s java -r **/*.class
    cd ..

    mkdir ${EXT_DIR2}
    cd ${EXT_DIR2}
    jar xf ${JAR_DIR}/${JAR_FILE2}
    jad -d . -o -t2 -safe -space -b -ff -s java -r **/*.class
    cd ..

    # remove class files so the diff is clean
    ${FIND} ${TEMP_DIR} -name '*.class' | xargs rm

    # diff recursively

I can run it on Windows using GIT for Windows. Just open a command prompt. Run bash and then execute the script from there.

Answer 8

Use Java Decompiler to turn the jar file into source code file, and then use WinMerge to perform comparison.

You should consult the copyright holder of the source code, to see whether it is OK to do so.

Answer 9

Here's an aparently free tool http://www.extradata.com/products/jarc/

Answer 10

Please try http://www.osjava.org/jardiff/ - tool is old and the dependency list is large. From the docs, it looks like worth trying.

Answer 11

use java decompiler and decompile all the .class files and save all files as project structure .

then use meld diff viewer and compare as folders ..