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

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1- Die File aktualisieren und auf der Festplatte speichern

Im Dokument führe ich Sie bei der Hochladung der File und die Speicherung der File auf dem Harddisk. das Beispiel benutzt Servlet API >= 3.0.
Notiz: Sie können eine ähnliche Hinweise von der Hochladung und Herunterladung einer File aus Database durch die Benutzung des Servlet lesen bei ...:

2- Zum Beispiel : Die File hochladen

Das Beispiel: die File hochladen und in einem Ordner des Harddisk speichern
UploadFileServlet.java
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;
    }

}
UploadFileResultsServlet.java
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);
   }

}
/WEB-INF/jsps/uploadFile.jsp
<!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>
/WEB-INF/jsps/uploadFileResults.jsp
<!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>
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