File转换成MultiPartFile

public FileItem createFileItem(String filePath) {
    FileItemFactory factory = new DiskFileItemFactory(16, null);
    String textFieldName = "textField";
    int num = filePath.lastIndexOf(".");
    String extFile = filePath.substring(num);
    String path = filePath.substring(0, num);
    path = path.replace("\\", "/");
    String[] fileNames = path.split("/");
    String fileName = fileNames[fileNames.length - 1];
    FileItem item = factory.createItem(textFieldName, "text/plain", true, fileName + extFile);
    File newfile = new File(filePath);
    int bytesRead = 0;
    byte[] buffer = new byte[8192];
    try {
        FileInputStream fis = new FileInputStream(newfile);
        OutputStream os = item.getOutputStream();
        while ((bytesRead = fis.read(buffer, 0, 8192)) != -1) {
            os.write(buffer, 0, bytesRead);
        }
        os.close();
        fis.close();
    } catch (IOException e) {
        e.printStackTrace();
    }
    return item;
}