Servlet从tomcat 7中的多部分表单获取参数

制作项目并需要上传文件。 所以，我使用enctype =“multipart / form-data”通知。

但我无法解析请求中的参数。 我也试过getPart，但它返回空字符串。

Servlet代码 – >

import java.io.File; import java.io.IOException; import java.io.PrintWriter; import java.util.List; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import org.apache.commons.fileupload.FileItem; import org.apache.commons.fileupload.disk.DiskFileItemFactory; import org.apache.commons.fileupload.servlet.ServletFileUpload; public class upload_wall extends HttpServlet { private static final long serialVersionUID = 1L; // location to store file uploaded private static final String UPLOAD_DIRECTORY = "image_upload"; // upload settings private static final int MEMORY_THRESHOLD = 1024 * 1024 * 3; // 3MB private static final int MAX_FILE_SIZE = 1024 * 1024 * 40; // 40MB private static final int MAX_REQUEST_SIZE = 1024 * 1024 * 50; // 50MB protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html"); PrintWriter out = response.getWriter(); // checks if the request actually contains upload file if (!ServletFileUpload.isMultipartContent(request)) { // if not, we stop here PrintWriter writer = response.getWriter(); writer.println("Error: Form must has enctype=multipart/form-data."); writer.flush(); return; } // configures upload settings DiskFileItemFactory factory = new DiskFileItemFactory(); // sets memory threshold - beyond which files are stored in disk factory.setSizeThreshold(MEMORY_THRESHOLD); // sets temporary location to store files factory.setRepository(new File(System.getProperty("java.io.tmpdir"))); ServletFileUpload upload = new ServletFileUpload(factory); // sets maximum size of upload file upload.setFileSizeMax(MAX_FILE_SIZE); // sets maximum size of request (include file + form data) upload.setSizeMax(MAX_REQUEST_SIZE); // constructs the directory path to store upload file // this path is relative to application's directory String uploadPath = getServletContext().getRealPath("") + File.separator + UPLOAD_DIRECTORY; // creates the directory if it does not exist File uploadDir = new File(uploadPath); if (!uploadDir.exists()) { uploadDir.mkdir(); } try { @SuppressWarnings("unchecked") List formItems = upload.parseRequest(request); String fileName1 = ""; if (formItems != null && formItems.size() > 0) { for (FileItem item : formItems) { // processes only fields that are not form fields if (!item.isFormField()) { String fileName = new File(item.getName()).getName(); fileName1 += fileName; String filePath = uploadPath + File.separator + fileName; File storeFile = new File(filePath); // saves the file on disk item.write(storeFile); } } } String p_text = request.getParameter("p_data"); String gallery_nm = request.getParameter("upload_wall_gallery"); out.println(p_text); out.println(gallery_nm); //out.println("Upload has been done successfully!"+fileName1); } catch (Exception ex) { out.println(ex.getMessage()); } } } 

我无法在net或stackoverflow上找到一个有效的例子。

有什么简单的解决

Answer 1

问题出在这里：

 String p_text = request.getParameter("p_data"); String gallery_nm = request.getParameter("upload_wall_gallery"); 

从如何使用JSP / Servlet将文件上传到服务器？ 回答 ，你应该把你的参数作为FileItem获取， isFormField()方法返回true 。 从答案中发布相关的代码片段：

 for (FileItem item : formItems) { if (item.isFormField()) { // Process regular form field (input type="text|radio|checkbox|etc", select, etc). String fieldname = item.getFieldName(); String fieldvalue = item.getString(); // ... (do your job here) } else { // Process form file field (input type="file"). String fieldname = item.getFieldName(); String filename = FilenameUtils.getName(item.getName()); InputStream filecontent = item.getInputStream(); // ... (do your job here) } } 

解决方案：在调用if (!item.isFormField())时将其他请求参数处理移动到else部分。

 for (FileItem item : formItems) { // processes only fields that are not form fields if (!item.isFormField()) { String fileName = new File(item.getName()).getName(); fileName1+=fileName; String filePath = uploadPath + File.separator + fileName; File storeFile = new File(filePath); // saves the file on disk item.write(storeFile); } else { //here... String fieldname = item.getFieldName(); String fieldvalue = item.getString(); if (fieldname.equals("p_data")) { //logic goes here... } else if (fieldname.equals("upload_wall_gallery")) { //next logic goes here... } } } 

Answer 2

由于它是一个multipart/form-dataforms，对request.getParameter()的调用将始终返回null。 在这种情况下，您需要做的是

  if (item.isFormField()) { System.out.println("Got a form field: " + item.getFieldName()+ " " +item.getString()); } else { // it is a file process, the way you are doing it } 

我希望每件事都能正常运作。