@MultipartConfig
使用註解@MultipartConfig 將一個 Servlet 標識為支援檔案上傳。Servlet3.0 將
multipart/form-data 的 POST 請求封裝成 Part，通過 Part 對檔案進行上傳。
Servlet3 沒有提供直接獲取檔名的方法,需要從請求頭中解析出來

upload.html

<form action="upload" method="post" enctype="multipart/form-data">
<input type="file" name="f">
<br/>
<input
 
 type="submit" name="submit">
</form>

UploadServlet//request.getpart()單檔案上傳

@WebServlet("/upload")
@MultipartConfig
public class UploadServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    public UploadServlet() {}

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws
 
 ServletException, IOException {
        request.setCharacterEncoding("UTF-8");
        response.setContentType("text/html;charset=UTF-8");

        // 獲取請求項， 封裝成Part物件
        Part part = request.getPart("f");

        String fileName = part.getSubmittedFileName();
        System.out.println(fileName);

        String direc = this
 
.getServletContext().getRealPath("/upload/");
        File dirf = new File(direc);

        if(!dirf.exists()){
            dirf.mkdirs();
        }
        part.write(direc+fileName);
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) 
            throws ServletException, IOException {
        doGet(request, response);
    }

}

使用request.getParts() 多檔案上傳

        request.setCharacterEncoding("UTF-8");
        response.setContentType("text/html;charset=UTF-8");

        Collection<Part> parts = request.getParts();

        for(Part part:parts){
            String fileName = part.getSubmittedFileName();
            System.out.println(fileName);

            if(null!=fileName&&!(fileName).trim().equals("")){

                String direc = this.getServletContext().getRealPath("/upload/");
                File dirf = new File(direc);

                if(!dirf.exists()){
                    dirf.mkdirs();
                }
                part.write(direc+fileName);
            }

        }