Question

我正在创建一个Web应用程序。用户上传ARF文件，我的应用程序将其转换为WMV格式。我目前正在对需要转换的文件名进行硬编码，为了避免这种情况，我需要能够传入上传视频时输入的文件名，然后只需更改扩展名（.arf更改为.wmv）转换。

upload.jsp检索上传文件的名称并执行转换：

<%@ page import="java.io.*"%>
<%
    String saveFile = "";
    String contentType = request.getContentType();
    if ((contentType != null) && (contentType.indexOf("multipart/form-data") >= 0)) {
        DataInputStream in = new DataInputStream(request.getInputStream());
        int formDataLength = request.getContentLength();
        byte dataBytes[] = new byte[formDataLength];
        int byteRead = 0;
        int totalBytesRead = 0;
        while (totalBytesRead < formDataLength) {
            byteRead = in.read(dataBytes, totalBytesRead, formDataLength);
            totalBytesRead += byteRead;
        }
        String file = new String(dataBytes);
        saveFile = file.substring(file.indexOf("filename=\"") + 10);
        saveFile = saveFile.substring(0, saveFile.indexOf("\n"));
        saveFile = saveFile.substring(saveFile.lastIndexOf("\\") + 1, saveFile.indexOf("\""));
        int lastIndex = contentType.lastIndexOf("=");
        String boundary = contentType.substring(lastIndex + 1, contentType.length());
        int pos;
        pos = file.indexOf("filename=\"");
        pos = file.indexOf("\n", pos) + 1;
        pos = file.indexOf("\n", pos) + 1;
        pos = file.indexOf("\n", pos) + 1;
        int boundaryLocation = file.indexOf(boundary, pos) - 4;
        int startPos = ((file.substring(0, pos)).getBytes()).length;
        int endPos = ((file.substring(0, boundaryLocation)).getBytes()).length;
        String saveFile2 = "C:/Webex/" +saveFile;
        File ff = new File(saveFile2);
        FileOutputStream fileOut = new FileOutputStream(ff);
        fileOut.write(dataBytes, startPos, (endPos - startPos));
        fileOut.flush();
        fileOut.close();

        try {  
            Process p = Runtime.getRuntime().exec("cmd /C C:/Users/dheerajg/Desktop/webex2.vbs");
            p.waitFor();
        } catch (IOException e) {  
            e.printStackTrace();  
        }
    }
%>

<table border="2">
    <tr>
        <td><b>You have successfully converted the file by the name of:</b>
        <%
            out.println(saveFile);                
        %>
        </td>
    </tr>
</table>

<HTML>
<HEAD>
    <TITLE>Display file upload form to the user</TITLE>
</HEAD>
<BODY>
    <FORM ENCTYPE="multipart/form-data" ACTION="download.jsp" METHOD=POST>
        <br> <br> <br>
        <tr>
            <td colspan="2" align="center"><input type="submit"
                value="Download the recording"></td>
        </tr>
    </FORM>
</BODY>
</HTML>

注意：String saveFile包含上传文件的文件名。转换转换后，将调用download.jsp：

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
   pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Download Servlet Test</title>
</head>
<body>
Click on the link to download: <a href="DownloadServlet">Download Link</a>
</body>
</html>

当用户点击下载链接时，它会执行Servlet DownloadServlet.java：

import java.io.DataInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class DownloadServlet extends javax.servlet.http.HttpServlet implements
        javax.servlet.Servlet {
    static final long serialVersionUID = 1L;
    private static final int BUFSIZE = 4096;
    private String filePath;

    public void init() {
        filePath = "C:/Webex/DEMO-20131128 2211-1(1).wmv"; // Notice how the name of the converted video has been hardcoded.
    }

    protected void doGet(HttpServletRequest request,
            HttpServletResponse response) throws ServletException, IOException {
        File file = new File(filePath);
        int length   = 0;
        ServletOutputStream outStream = response.getOutputStream();
        ServletContext context  = getServletConfig().getServletContext();
        String mimetype = context.getMimeType(filePath);

        // sets response content type
        if (mimetype == null) {
            mimetype = "application/octet-stream";
        }
        response.setContentType(mimetype);
        response.setContentLength((int)file.length());
        String fileName = (new File(filePath)).getName();

        // sets HTTP header
        response.setHeader("Content-Disposition", "attachment; filename=\"" + fileName + "\"");

        byte[] byteBuffer = new byte[BUFSIZE];
        DataInputStream in = new DataInputStream(new FileInputStream(file));

        // reads the file's bytes and writes them to the response stream
        while ((in != null) && ((length = in.read(byteBuffer)) != -1))
        {
            outStream.write(byteBuffer,0,length);
        }

        in.close();
        outStream.close();
    }
}

为避免转换后的文件被硬编码，我希望能够将saveFile变量传递给此类（并将.arf替换为.wmv）。我怎么能这样做？我想在saveFile文件中公开upload.jsp变量，但编译器不允许我这样做。

Answer 1

你应该将输出文件名作为url参数传递

在upload.jsp

中

<%
   String resultFile = saveFile.replaceAll(".arf", ".wmv");
%>

<html>
   <body>
      Your file successfully converted<br />
      Click <a href="downloadservlet.jsp?f=<%= resultFile %>">here</a> to download<br />
  </body>

在downloadServlet doGet（）

中的

resultFile = request.getParameter("f");
filePath = "C:/Webex/" + resultFile;

根本不需要download.jsp。

Answer 2

假设您希望将文件下载限制为上载它的用户，您可以使用文件路径字符串值存储会话属性。在下载servlet中，您可以引用相同的会话属性并将其值用作文件系统路径。

upload.jsp：

session.setAttribute("filePath", saveFile);

在DownloadServlet.java中，删除实例变量声明（您希望这是每个用户，不在所有用户之间共享）filePath，然后在doGet()内添加：

String filePath = (String) session.getAttribute("filePath");

如果没有填充，请务必检查它是否为空。

从JSP文件访问变量到Java Servlet

2 个答案: