How to copy file inside jar to outside the jar?

Question

I want to copy a file from a jar. The file that I am copying is going to be copied outside the working directory. I have done some tests and all methods I try end up with 0

Answer 1

${JAVA_HOME}/bin/jar -cvf /path/to.jar

Answer 2

Faster way to do it with Java 7+ , plus code to get the current directory:

   /**
     * Copy a file from source to destination.
     *
     * @param source
     *        the source
     * @param destination
     *        the destination
     * @return True if succeeded , False if not
     */
    public static boolean copy(InputStream source , String destination) {
        boolean succeess = true;

        System.out.println("Copying ->" + source + "\n\tto ->" + destination);

        try {
            Files.copy(source, Paths.get(destination), StandardCopyOption.REPLACE_EXISTING);
        } catch (IOException ex) {
            logger.log(Level.WARNING, "", ex);
            succeess = false;
        }

        return succeess;

    }

---

Testing it (icon.png is an image inside the package image of the application):

copy(getClass().getResourceAsStream("/image/icon.png"),getBasePathForClass(Main.class)+"icon.png");

---

About the line of code (getBasePathForClass(Main.class)): -> check the answer i have added here :) -> Getting the Current Working Directory in Java

Answer 3

To copy a file from your jar, to the outside, you need to use the following approach:

1. Get a InputStream to a the file inside your jar file using getResourceAsStream()
2. We open our target file using a FileOutputStream
3. We copy bytes from the input to the output stream
4. We close our streams to prevent resource leaks

Example code that also contains a variable to not replace the existing values:

public File saveResource(String name) throws IOException {
    return saveResource(name, true);
}

public File saveResource(String name, boolean replace) throws IOException {
    return saveResource(new File("."), name, replace)
}

public File saveResource(File outputDirectory, String name) throws IOException {
    return saveResource(outputDirectory, name, true);
}

public File saveResource(File outputDirectory, String name, boolean replace)
       throws IOException {
    File out = new File(outputDirectory, name);
    if (!replace && out.exists()) 
        return out;
    // Step 1:
    InputStream resource = this.getClass().getResourceAsStream(name);
    if (resource == null)
       throw new FileNotFoundException(name + " (resource not found)");
    // Step 2 and automatic step 4
    try(InputStream in = resource;
        OutputStream writer = new BufferedOutputStream(
            new FileOutputStream(out))) {
         // Step 3
         byte[] buffer = new byte[1024 * 4];
         int length;
         while((length = in.read(buffer)) >= 0) {
             writer.write(buffer, 0, length);
         }
     }
     return out;
}