boolean multipartContent = ServletFileUpload.isMultipartContent(request);
if (multipartContent==true) {
    DiskFileItemFactory fileItemFactory = new DiskFileItemFactory();
    ServletFileUpload upload = new ServletFileUpload(fileItemFactory);
    upload.setSizeMax(40 * 1024 * 1024);
    List<FileItem> fileItemList = upload.parseRequest(request);
    for (FileItem fileItem : fileItemList) {
        File file1 = new File("E:\\app\\" + fileItem.getName());
        try {
            fileItem.write(file1);
        } catch (Exception e) {
            e.printStackTrace();
        }

    }
}
response.sendRedirect("/hello.jsp");


maven配置:

<dependency>
  <groupId>commons-fileupload</groupId>
  <artifactId>commons-fileupload</artifactId>
  <version>1.3.3</version>
</dependency>
<dependency>
  <groupId>commons-io</groupId>
  <artifactId>commons-io</artifactId>
  <version>2.4</version>
</dependency>

簡單的servlet上傳文件