Hochladen und Herunterladen von Dateien die auf der Festplatte mit Java Servlet gespeichert sind

package org.o7planning.servletexamples;

import java.io.File;
import java.io.IOException;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.annotation.MultipartConfig;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.Part;

@WebServlet("/uploadFile")
@MultipartConfig(fileSizeThreshold = 1024 * 1024 * 2, // 2MB
        maxFileSize = 1024 * 1024 * 10, // 10MB
        maxRequestSize = 1024 * 1024 * 50) // 50MB
public class UploadFileServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    public static final String SAVE_DIRECTORY = "uploadDir";

    public UploadFileServlet() {
        super();
    }

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        RequestDispatcher dispatcher = request.getServletContext().getRequestDispatcher("/WEB-INF/jsps/uploadFile.jsp");

        dispatcher.forward(request, response);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        try {
            String description = request.getParameter("description");
            System.out.println("Description: " + description);

            // Gets absolute path to root directory of web app.
            String appPath = request.getServletContext().getRealPath("");
            appPath = appPath.replace('\\', '/');

            // The directory to save uploaded file
            String fullSavePath = null;
            if (appPath.endsWith("/")) {
                fullSavePath = appPath + SAVE_DIRECTORY;
            } else {
                fullSavePath = appPath + "/" + SAVE_DIRECTORY;
            }

            // Creates the save directory if it does not exists
            File fileSaveDir = new File(fullSavePath);
            if (!fileSaveDir.exists()) {
                fileSaveDir.mkdir();
            }

            // Part list (multi files).
            for (Part part : request.getParts()) {
                String fileName = extractFileName(part);
                if (fileName != null && fileName.length() > 0) {
                    String filePath = fullSavePath + File.separator + fileName;
                    System.out.println("Write attachment to file: " + filePath);
                    // Write to file
                    part.write(filePath);
                }
            }
            // Upload successfully!.
            response.sendRedirect(request.getContextPath() + "/uploadFileResults");
        } catch (Exception e) {
            e.printStackTrace();
            request.setAttribute("errorMessage", "Error: " + e.getMessage());
            RequestDispatcher dispatcher = getServletContext().getRequestDispatcher("/WEB-INF/jsps/uploadFile.jsp");
            dispatcher.forward(request, response);
        }
    }

    private String extractFileName(Part part) {
        // form-data; name="file"; filename="C:\file1.zip"
        // form-data; name="file"; filename="C:\Note\file2.zip"
        String contentDisp = part.getHeader("content-disposition");
        String[] items = contentDisp.split(";");
        for (String s : items) {
            if (s.trim().startsWith("filename")) {
                // C:\file1.zip
                // C:\Note\file2.zip
                String clientFileName = s.substring(s.indexOf("=") + 2, s.length() - 1);
                clientFileName = clientFileName.replace("\\", "/");
                int i = clientFileName.lastIndexOf('/');
                // file1.zip
                // file2.zip
                return clientFileName.substring(i + 1);
            }
        }
        return null;
    }

}

package org.o7planning.servletexamples;

import java.io.IOException;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

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


   public UploadFileResultsServlet() {
       super();
   }

   @Override
   protected void doGet(HttpServletRequest request, HttpServletResponse response)
           throws ServletException, IOException {

       RequestDispatcher dispatcher
           = request.getServletContext().getRequestDispatcher("/WEB-INF/jsps/uploadFileResults.jsp");

       dispatcher.forward(request, response);
   }

}

<!DOCTYPE >
<html>
<head>
<title>Upload files</title>
</head>
<body>

    <div style="padding:5px; color:red;font-style:italic;">
       ${errorMessage}
    </div>
   
    <h2>Upload Files</h2>

    <form method="post" action="${pageContext.request.contextPath}/uploadFile"
        enctype="multipart/form-data">
       
        Select file to upload:
        <br />
        <input type="file" name="file"  />
        <br />
        <input type="file" name="file" />
        <br />
        Description:
        <br />
        <input type="text" name="description" size="100" />
        <br />
        <br />
        <input type="submit" value="Upload" />
    </form>
   
</body>
</html>

<!DOCTYPE >
<html>
<head>
<title>Upload files</title>
</head>
<body>

    <h3>Upload has been done successfully!</h3>
    <a href="${pageContext.request.contextPath}/uploadFile">Continue Upload</a>
     
   
</body>
</html>