org内的Java-copy file.txt，这是A.jar中的一个文件夹，而没有提取z.jar文件

Question

I was trying to copy a file into a A.jar (without extracting it) but it didn't work. Suppose I have file "copy.txt" in "D:\\java\\copy.txt" and i want this file to be copied into my "A.jar/org/here" . if the file is already exist then it should replace it.

i tried modifying the below code but it didn't work.

import java.io.IOException;
import java.nio.file.FileSystem;
import java.nio.file.FileSystems;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;

public class deploy {
public static void main(String[] argv) {
    Path myFilePath = Paths.get("C:/Users/ma329300/Desktop/copy.txt");

    Path zipFilePath = Paths.get("D:/java/A.jar");
    try( FileSystem fs = FileSystems.newFileSystem(zipFilePath, null) ){
        Path fileInsideZipPath = fs.getPath("/org/copy.txt");
        Files.copy(myFilePath, fileInsideZipPath);
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}
}

Answer 1

First of all, check your paths. Java is really tricky with the paths and should be in full path form. Try putting the backslashes like "D:\\java\\A.jar", as windows works differently than linux.

Also, if you change your file and re-compile, it will generate a new .jar each time, with the updated file you wanted to change. That would solve your problem without having to access your .jar externally.

I tried once to access libraries packed on a .jar and load them with the code inside the .jar too and didn't worked propperly, so be carefull.

Another thing you should be aware of is that you cannot modify a .jar directly without decompressing, as it uses a special algorythm in order to get the indexation properly done for and by java. Changing one specific part of the .jar could corrupt the data into it and make it crash on the run.

Hope it helped.