Question

我已经实施了拖放功能在jsp和servlet中删除文件上传，但是我遇到了问题。以下是我的upload.jsp代码的一部分：

   function dropUpload(event) {
        var files = event.dataTransfer.files;
        upload(files);
    }

    function upload(files) {
        var formData = new FormData();
        for (var i in files) {
            formData.append('file[]', files[i]);
         }

        var xhr = new XMLHttpRequest();
        xhr.onload = function() {
            console.log(xhr.responseText);
        };
        xhr.open("POST", "UploadServlet"); 
        xhr.send(formData);
    }

我在getParts()代码中使用UploadServlet.java方法获取用户上传的文件，如下所示：

public class UploadServlet extends HttpServlet {
private static final long serialVersionUID = 1L;

/**
 * @see HttpServlet#HttpServlet()
 */
public UploadServlet() {
    super();
    // TODO Auto-generated constructor stub
}

/**
 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
 */
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    request.getRequestDispatcher("login.jsp").forward(request, response);
}

/**
 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
 */
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {


    String savePath = "D:\\TEST";
    // creates the save directory if it does not exists
    File fileSaveDir = new File(savePath);
    if (!fileSaveDir.exists()) {
        fileSaveDir.mkdir();
    }
    response.getWriter().println(request.getParts().size());
    for (Part part : request.getParts()) {
        if(part.getContentType() == null) {
            continue;
        }
        response.getWriter().println("Part name: " + part.getName());
        response.getWriter().println("Size: " + part.getSize());
        response.getWriter().println("Content Type: " + part.getContentType());
        String fileName = extractFileName(part, response);
        response.getWriter().println(fileName);
        part.write(savePath + File.separator + fileName);
        response.getWriter().println("already upload file:" + fileName);
        response.getWriter().println("=============================================");
    }

}

 private String extractFileName(Part part,HttpServletResponse response) throws IOException {
        String contentDisp = part.getHeader("content-disposition");
        //response.getWriter().println(contentDisp);
        String[] items = contentDisp.split(";");
        for (String s : items) {
            if (s.trim().startsWith("filename")) {
                return s.substring(s.indexOf("=") + 2, s.length()-1);
            }
        }
        return "";
    }

但我无法理解，如果我使用upload.jsp上传2个文件， getParts().size()的值为4;这意味着我总是有2个文件，而不是我上传的文件，2个外部文件名和contentType将为null，这将导致part.write()中的错误。

我的解决方案是使用if语句

if(part.getContentType() == null) {
            continue; }

忽略空文件。

有人能告诉我为什么会这样吗？

servlet getParts（）在上传文件中

0 个答案: