java：将文件添加到jar目录

Question

I am working on a project which requires users to upload a Java file which can be later compiled into a class file. I have already written the code for uploading the file to the project folder. It works perfectly when launched using Eclipse. The problem arises when I package the project as a JAR. The code throws an exception. I understand the reason.. when we package the project, only the class files are loaded in JAR and not the source files, and the location of the JAR file also makes a difference.

Let me explain what I have done and what I need to do:

In the IDE version of the project, I have something like:
where the user can browse for a file and click on the upload button to add it to the project structure. This works perfectly with the following code:

String path = Paths.get(".").toAbsolutePath().normalize().toString()+"\\path\\to\\directory";
File source=new File(textField1.getText());
String fileName="";
try {
    fileName=new java.io.File(textField1.getText()).getName();
    Files.copy(source.toPath(),new java.io.File(path+fileName).toPath(),REPLACE_EXISTING);
} catch (IOException e2) {
    e2.printStackTrace();
}

When I have to run the same code using a JAR file, I understand that I am supposed to change how I fetch the root directory of the project and then navigate to the required directory. Somehow, I can't get it working. I have already tried the following:

URL location=MainClass.class.getProtectionDomain().getCodeSource().getLocation();
String p = URLDecoder.decode(location.getFile(), "UTF-8");
System.out.println(location);

This prints rsrc:./ . How can I copy the uploaded file to the required directory within the Jar file?

I also tried another approach where I thought of creating a shell script to execute jar uf jar-file input-file(s) . I put the JAR file and this shell script in the same directory, and execute the following code:

try {
        String fileName = "shellFile.sh";
        URL location=MainClass.class.getProtectionDomain().getCodeSource().getLocation();
        String p = URLDecoder.decode(location.getFile(), "UTF-8");
        System.out.println(location);
        String inputFilePath = p + fileName;
        System.out.println(inputFilePath);
        Process process = Runtime.getRuntime().exec(inputFilePath);
    } catch (IOException e2) {
        // TODO Auto-generated catch block
        e2.printStackTrace();
    }

but I get the following exception:

java.io.IOException: Cannot run program "./shellFile.sh": CreateProcess error=2, The system cannot find the file specified at java.lang.ProcessBuilder.start(Unknown Source)

Is there any way I can upload a file to a directory within the JAR file?

Answer 1

String cmd = "jar uvf " + <jar file name> + " " + <name of file to be added;
System.out.println(cmd);
Process p = Runtime.getRuntime().exec(cmd);