java - 在 'handled' 相同表单的文本字段后，文件未上传

Question

以下 Servlet 处理照片和该照片的标题的上传。 servlet 工作正常(将照片上传到请求的目录)，直到添加了处理相同来源的文本字段的逻辑。现在它既不上传照片也不将标题提交到数据库。该表单的 enctype 为 multipart/form-data。

HTML

    <form method="post" action="UploadHandler" enctype="multipart/form-data">
        <table>

            <tr>
                <td> <strong> Browse photo to submit </strong> </td>
                <td> <input type="file" name="ImageToUpload" value="Upload Photo"/> </td>
            </tr>

            <tr>
                <td> <strong> Give a Caption to this photo </strong>  </td>
                <td> <input type="text" name="CaptionBox" size="40" /></td>
            </tr>

            <tr>
                <td> <strong> Tags &nbsp;<a href="#"> <i> Browse tags </i> </a> </strong> </td>
                <td> <input type="text" size="20" value="Tags" id="tagfield" style="color: #A0A0A4; font-size:16px;" onfocus="emptyTheDefaultValue()"> </td>
            </tr>
            <tr colspan="2">
                <td> <input type="submit" value="submit photo"/> </td>
            </tr>

        </table>
 </form>

处理上传的Servlet

package projectcodes;

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.IOException;
import java.io.PrintWriter;
import java.io.File;
import java.util.List;
import java.util.Iterator;
import org.apache.commons.fileupload.*;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
import org.apache.commons.io.FilenameUtils;
import NonServletFiles.HandleCaption;
import NonServletFiles.ChangePartToString;

public class UploadHandler extends HttpServlet {
@Override
public void doPost(HttpServletRequest request,HttpServletResponse response) throws IOException,ServletException {
    response.setContentType("text/plain");
    String path = request.getParameter("ImageToUpload"); 
    // Now handle the caption
    // Note : They have a multipart/form-data request
    // Using the servlet API 3.0
    ChangePartToString cpts = new ChangePartToString(request.getPart("CaptionBox")); // get the CaptionBox part 
    String caption = null;

        try {
            caption = cpts.getValue();
            System.out.println(caption); // <<-------- I get this value fine
        }catch(Exception exc) {
            exc.printStackTrace();
            System.out.println(exc);
        }

    PrintWriter writer = response.getWriter();
    try {
        Boolean isMultipart = ServletFileUpload.isMultipartContent(request);
        if(!isMultipart) {
            Boolean AttemptToUploadFile = true;
            RequestDispatcher rd = request.getRequestDispatcher("portfolio_one.jsp");
            request.setAttribute("UploadAttempt", AttemptToUploadFile);
            rd.forward(request, response);
        } else {
            DiskFileItemFactory diskFileItem = new DiskFileItemFactory();
            ServletFileUpload fileUpload = new ServletFileUpload(diskFileItem);
            List list = null;

            try {
                list = fileUpload.parseRequest(request);
            }catch(Exception exc) {
            //                    Boolean AttemptToUploadFile = true;
            //                    RequestDispatcher rd = request.getRequestDispatcher("portfolio_one.jsp");
            //                    request.setAttribute("UploadAttempt", AttemptToUploadFile);
            //                    rd.forward(request, response);
                exc.printStackTrace();
                System.out.println(exc);
            }

            Iterator iterator = list.iterator();
            while(iterator.hasNext()) {
                String emailOfTheUser = null;
                FileItem fileItem = (FileItem)iterator.next();
                if(!fileItem.isFormField()) {
                    String fieldName = fileItem.getFieldName();
                    String fileName = FilenameUtils.getName(fileItem.getName());
                    HttpSession session = request.getSession();
                    if(!session.isNew()) {
                        emailOfTheUser = (String)session.getAttribute("Email");
                    }
                    File file = new File("/home/non-admin/project uploads/project users/" + emailOfTheUser ,fileName);
                    fileItem.write(file);
                    // now since the file has been uploaded , upload the caption to the photo  
                    System.out.println("THE CAPTION :" + caption);
                    HandleCaption hc = new HandleCaption(caption,emailOfTheUser,fileName);
                    hc.SubmitCaptionToTheDatabase(); // This calls invokes a method that submits a caption to the database
                    RequestDispatcher rd = request.getRequestDispatcher("portfolio_one.jsp");
                    String message = "File Uploaded successfully !";
                    request.setAttribute("SuccessMessage", message);
                    rd.forward(request, response);
                }
            }
        }
    }catch(Exception exc) {
        exc.printStackTrace();
        System.out.println(exc);
    }
}

}

标题字符串返回正常。文件未上传可能是什么原因。我在服务器日志中没有看到任何异常。

Answer 1

您将 Servlet 3.0 内置多部分解析器与 Apache Commons FileUpload 混合在一起。你不应该那样做。一旦请求正文被一个 API 解析，就无法再被另一个 API 解析。客户端不会多次重新发送相同的请求正文，因为服务器需要解析它。

删除 Apache Commons FileUpload。当已经使用 Servlet 3.0 内置的多部分解析器时，您不需要它。您只需向 servlet 类添加 @MultipartConfig 注释即可使多部分解析器对普通表单字段和文件字段正确工作。您也不应该使用 getParameterXxx() 方法。另请参阅How to upload files to server using JSP/Servlet?

以下是对代码的必要重写，以便获得这两个值:

@WebServlet("/UploadHandler")
@MultipartConfig
public class UploadHandler extends HttpServlet {

    @Override
    public void doPost(HttpServletRequest request,HttpServletResponse response) throws IOException,ServletException {
        Part imageToUpload = request.getPart("ImageToUpload");
        String imageFilename = getFilename(imageToUpload);
        InputStream imageContent = imageToUpload.getInputStream();
        String captionBox = getValue(request.getPart("CaptionBox"));

        // ...
    }

    private static String getFilename(Part part) {
        for (String cd : part.getHeader("content-disposition").split(";")) {
            if (cd.trim().startsWith("filename")) {
                String filename = cd.substring(cd.indexOf('=') + 1).trim().replace("\"", "");
                return filename.substring(filename.lastIndexOf('/') + 1).substring(filename.lastIndexOf('\\') + 1); // MSIE fix.
            }
        }
        return null;
    }

    private static String getValue(Part part) throws IOException {
        BufferedReader reader = new BufferedReader(new InputStreamReader(part.getInputStream(), "UTF-8"));
        StringBuilder value = new StringBuilder();
        char[] buffer = new char[1024];
        for (int length = 0; (length = reader.read(buffer)) > 0;) {
            value.append(buffer, 0, length);
        }
        return value.toString();
    }

}