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

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 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

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 6

• 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