Hand Edit A Jar to Change Package Names

Question

I have a jar file from an external source. All of the classes in the jar are in the com.xyz package.

I would like to move all of classes to the com.xyzold package.

Is this is simple as unzipping the jar, renaming the xzy folder to xyzold, and rezipping it, or do I need to modify each class file as well?

Here's my solution, using Jar Jar Links

java -jar jarjar-1.4.jar process rules.txt google-collections-1.0.jar google-collections-old-1.0.jar

And here's the contents of my rules.txt file:

rule com.google.** com.googleold.@1

They have a new project, which uses the same package and class names. It was supposed to be fully backward compatible but isn't. We have an very large codebase that depends on the old version. — Ben Noland, Dec 06 '12 at 15:50
That command line invocation doesn't work with the version of jarjar I found at https://github.com/hannesa2/jarjar/releases/tag/1.0.3. Parameters have to be passed with "--" e.g. `java -jar "jarjar-command-1.0.3.jar" --mode process --rules "rules.txt" in.jar --output out.jar` — abulka, May 23 '23 at 02:18

score 23 · Accepted Answer · answered Dec 06 '12 at 15:25

23

You can use Jar Jar Links to achieve that. Also you don't need the source code of the classes you'd like to modify, as the program does it on the bytecode level (ie. it modifies the .class files directly.)

answered Dec 06 '12 at 15:25

Maik Schreiber

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Is there something newer ? – expert Dec 08 '18 at 20:02
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@expert I used it and worked. Still sounds useful – Mahdi-Malv Jan 13 '22 at 09:03
@Mahdi-Malv how to used it I`ve been looking tutorial on youtube using the Jar Jar Links but couldn`t find one – Clinton Canarias Aug 11 '22 at 12:37
The only thing I remember is that I read the `--help` or `-h`. Use the jar's helper – Mahdi-Malv Aug 12 '22 at 09:34
Doesn't seem to work on classnames involving the `$` character? See https://github.com/shevek/jarjar/issues/29 – abulka May 23 '23 at 02:54

score 2 · Answer 2 · answered Dec 06 '12 at 15:25

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You can use the Maven shade plugin to do this in a Maven build.

answered Dec 06 '12 at 15:25

Hiery Nomus

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This worked for me. Though it did introduce extra classes from my project into the jar that I didn't need, so I had to delete them manually (by unzipping/zipping using jar) – abulka May 23 '23 at 22:46

score 1 · Answer 3 · answered Dec 06 '12 at 15:24

You should take a look at Jar Jar Links. (I'm not taking any responisibility for the name :).)

Its primary use case is to embed external jars in your own jar, and to do that, it can re-name existing packages. It changes the necessary byte code. You might be able to tweak it to do what you want.

score 1 · Answer 4 · answered Dec 06 '12 at 15:29

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You can probably do this with the ProGuard obfuscator. It can certainly move code around in packages and operates at the byte code level. Its primary aim is obfuscation though so one of the other options should certainly be looked at first.

answered Dec 06 '12 at 15:29

pillingworth

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score -4 · Answer 5 · answered Dec 06 '12 at 15:21

-4

No you need to modify all the classes in jar file. You need to have a source code in-order to change package.

answered Dec 06 '12 at 15:21

Pradeep Simha

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score -4 · Answer 6 · answered Dec 06 '12 at 15:21

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You would need to modify all the Java source files too. Not just the package names but the imports too, and any possible inline declarations. Not really worth it.

answered Dec 06 '12 at 15:21

Zutty

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Hand Edit A Jar to Change Package Names

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