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I was wondering if it was possible to extract the contents of a .jar file into a different directory, then add some files to that directory, and then compress the directory back into a .jar file, with the additions. A way of extracting the jar file i found was to use NSTask to execute the terminal command of jar xf (location of jar file). This worked, but it halted the UI of the program permanently (without crashing it), and unarchived the contents into the directory that the application was stored in, which was a slight mess to clean up. Is there another way of doing this, or am I using NSTask incorrectly? Here is the code I am using:

//Unarchive the jar
[self runCommandWithBase:@"/usr/bin/jar" arguments:[NSArray arrayWithObjects:@"xf", jarLocation, nil]];

and

- (NSString *)runCommandWithBase:(NSString *)base arguments:(NSArray *)arguments {
//Create the task
NSTask *task = [[NSTask alloc] init];

//Setup the task
[task setLaunchPath:base];
[task setArguments:arguments];
[task setStandardInput:[NSPipe pipe]];
[task setStandardOutput:[NSPipe pipe]];

//Set file handle
NSFileHandle *file = [[NSPipe pipe] fileHandleForReading];

//Run the command
[task launch];

//Return
NSData *returnData = [file readDataToEndOfFile];
return [[NSString alloc] initWithData:returnData encoding:NSUTF8StringEncoding];}

Is there maybe a way to include a java application in Xcode that will unarchive the files, add the other files, and then re-compress it? Then execute the java application with NSTask?

Thanks in Advance,

Ben

GravityScore
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  • *"..possible to extract the contents of a .jar .., then add some files ..back into a .jar file."* What is it you are actually trying to achieve by all this? It sounds as though the best solution might be to Jar the extra resources, then add them to the run-time class-path of the app. This would not necessarily require any change to the original Jar, though you might need to update the Manifest to add the extra Jar to the class-path. – Andrew Thompson Jan 30 '12 at 09:53
  • Note that the jar file format is the zip file format. If there is a zip library in obj-c, then that can be used to open and compress the jar file. There are some (possible) complications as the manifest might need to be first but in practice it's never been a problem. I commonly use a zip file editor when I need to modify my jars. – Erik Jan 30 '12 at 10:05

1 Answers1

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A .jar file is nothing more than a .zip file with a different extension. You can probably open it with any lib that would otherwise open ZIP files.

Depending on what you change and how the JAR was built, though, you might need to update the manifest.mf file on /META-INF/ to reflect changes to the checksum.

Marcelo
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  • Thanks for the reply! I'll try using one of the open source zip file libraries, as Apple don't provide their own. I'm writing the application to replace a manual method I use to use, and when ever I did the manual method, I always just deleted the META-INF file. – GravityScore Jan 30 '12 at 14:34
  • I implemented your method this morning, and it worked brilliantly! Thanks so much for the answer. – GravityScore Jan 31 '12 at 09:55