Creation ZipDirectory empty java

Question

I want to create a ZipDirectory with my all files but when I create it, it's an empty directory. There are no files. I verify the length of my files and there are a length so I don't understand why my ZipDirectory is empty.

How can I solve my problem?

@Override
public byte[] zipResourceDirectory(String path, String directory, ApiParam api) throws IOException {

    //creating byteArray stream, make it bufforable and passing this buffor to ZipOutputStream
    ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
    BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(byteArrayOutputStream);
    ZipOutputStream zipOutputStream = new ZipOutputStream(bufferedOutputStream);         

    String prefix = directory;

    zipDirectory(api, zipOutputStream, path, prefix, directory);     

    zipOutputStream.finish();
    zipOutputStream.flush();

    return byteArrayOutputStream.toByteArray();        
}

private void zipDirectory(ApiParam api, ZipOutputStream zipOutputStream, String path, String prefix, String directory) throws IOException {

    try {

        Assert.notNull(api, "api is empty");
        Assert.notNull(zipOutputStream, "zipOutputStream is empty");
        Assert.notNull(path, "prefix is empty");
        Assert.notNull(directory, "directory is empty");

        ClassLoader classLoader = getClass().getClassLoader();
        File folder = new File(classLoader.getResource(path).getFile());
        System.out.println(folder.getAbsolutePath());
        Assert.notNull(directory, "folder is empty");
        File[] listOfFiles = folder.listFiles();
        Assert.notNull(listOfFiles, "listOfFiles is empty");

        for (int i = 0; i < listOfFiles.length; i++) {

            if (listOfFiles[i].isFile()) {

                addFileToZip(api, zipOutputStream, prefix ,listOfFiles[i], directory);

            } else if (listOfFiles[i].isDirectory()) {

                addDrirectoryToZip(api, zipOutputStream, path, prefix, listOfFiles[i]);
            }
        }            
    }
    catch (Exception e) {

        System.out.println(e);
    }           
}    

private void addDrirectoryToZip(ApiParam api, ZipOutputStream zipOutputStream, String path, String prefix, File file) throws IOException {

    try {

        Assert.notNull(api, "api is empty");
        Assert.notNull(zipOutputStream, "zipOutputStream is empty");
        Assert.notNull(path, "prefix is empty");
        Assert.notNull(file, "file is empty");

        zipOutputStream.putNextEntry(new ZipEntry(prefix + "/" + file.getName() + "/"));
        zipOutputStream.closeEntry();
        System.out.println("Directory " + file.getName());

        zipDirectory(api, zipOutputStream, path + "/" + file.getName(), prefix + "/" + file.getName(), file.getName());            
    }
    catch (Exception e) {

        System.out.println(e);
    }                  
}    

private void addFileToZip(ApiParam api, ZipOutputStream zipOutputStream, String prefix, File file, String directory) throws IOException {

    try {

        Assert.notNull(api, "api is empty");
        Assert.notNull(zipOutputStream, "zipOutputStream is empty");
        Assert.notNull(file, "file is empty");            
        Assert.notNull(directory, "directory is empty");  

        System.out.println("File " + file.getName());

        if (file.getName().equals("template_v1.xml")) {
            zipOutputStream.putNextEntry(new ZipEntry(prefix + "/"+api.getProxyName()+"_"+api.getVersion()+".xml"));
        }
        else {
            zipOutputStream.putNextEntry(new ZipEntry(prefix + "/" + file.getName()));
        }

        System.out.println("File2" + file.getName());

        FileInputStream fileInputStream = new FileInputStream(file);

        StringBuilder builder = new StringBuilder();
        int ch;
        while ((ch = fileInputStream.read()) != -1){
            builder.append((char) ch);
        }

        String outputString = fileBuilderService.build(directory, file.getName(), builder.toString(), api);

        InputStream inputStream = new ByteArrayInputStream(outputString.getBytes());

        int length;
        byte[] bytes = new byte[1024];
        while ((length = inputStream.read(bytes)) > 0) {
                zipOutputStream.write(bytes, 0, length);
        }

        inputStream.close();
        fileInputStream.close();
        zipOutputStream.closeEntry();              
    }
    catch (Exception e) {

        System.out.println(e);    
    }
}    

Thanks a lot.