Writing to a file inside a jar file

[Kumar Jaya]

Is there a way I can modify the contents of a file inside a jar file? I have tried different options but haven't succeeded. I just have a war file that does not have any contents inside the classes folder, but has all the working code inside the lib folder (jars). One of these jar files say (my1.jar) has a text file say (sample.txt) packaged along with it. I am able to read the contents of the file (sample.txt) from the code in my1.jar using (getClass().getResourceAsStream("path to sample.txt")). I just am curious to know whether I will be allowed to modify the content of the file (sample.txt).

my.war
|
|---META-INF
|
|---WEB-INF
|
|-- classes (empty)
|
|--lib
|
|---my1.jar
|---my2.jar

my1.jar
|
|--- META-INF
|--- com
|--my
| |
| |--file
| |
| |--sample.txt
|--MyClass (I am able to read the contents of the file from this class)

I am not able to create a file object of 'sample.txt' file. The Url obtained just does not start with 'file://..'(hierarchial) its opaque as ('jar:file://....'). I dont have a way to created a output stream either!

Any help is greatly appreciated.

Regards

[Rob Spoor]

It's simply not possible. JAR (and ZIP, which is the basis of JAR) doesn't allow actual writing into it. Any tool that apparently allows you to do this will create a temporary file with the new contents, then rename the temporary file to the old file.

With JAR files this is going to be even a bit harder, since the JVM locks the JAR files it loads. You can't modify or replace them until after the JVM exits.