Debian下JSP如何实现文件上传下载 - 问答

在Debian系统下，使用JSP实现文件上传和下载需要以下几个步骤：

安装Java环境

确保你的Debian系统已经安装了Java运行环境。如果没有，请使用以下命令安装：

sudo apt-get update
sudo apt-get install default-jdk

安装Tomcat服务器

在Debian系统上安装Tomcat服务器：

sudo apt-get install tomcat9

启动Tomcat服务器：

sudo systemctl start tomcat9

设置Tomcat开机自启：

sudo systemctl enable tomcat9

创建JSP文件

在你的Tomcat Web应用中创建一个JSP文件，例如fileUpload.jsp，并添加以下代码：

<%@ page import="java.io.*, java.util.*, org.apache.commons.fileupload.*, org.apache.commons.fileupload.disk.*, org.apache.commons.fileupload.servlet.*" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>File Upload</title>
</head>
<body>
    <form action="upload" method="post" enctype="multipart/form-data">
        <input type="file" name="file" />
        <input type="submit" value="Upload" />
    </form>
</body>
</html>

配置Tomcat

编辑/etc/tomcat9/webapps/your-webapp/WEB-INF/web.xml文件，添加以下代码以配置文件上传：

<servlet>
    <servlet-name>FileUploadServlet</servlet-name>
    <servlet-class>org.apache.commons.fileupload.servlet.ServletFileUpload</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>FileUploadServlet</servlet-name>
    <url-pattern>/upload</url-pattern>
</servlet-mapping>

实现文件上传

创建一个Java类（例如FileUploadServlet.java），并实现文件上传功能：

import java.io.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;
import org.apache.commons.fileupload.*;
import org.apache.commons.fileupload.disk.*;
import org.apache.commons.fileupload.servlet.*;

public class FileUploadServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
    private static final String UPLOAD_DIRECTORY = "uploads";

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        if (ServletFileUpload.isMultipartContent(request)) {
            try {
                List<FileItem> multiparts = new ServletFileUpload(new DiskFileItemFactory()).parseRequest(request);
                for (FileItem item : multiparts) {
                    if (!item.isFormField()) {
                        String name = new File(item.getName()).getName();
                        item.write(new File(UPLOAD_DIRECTORY + File.separator + name));
                        response.getWriter().println("File uploaded successfully: " + name);
                    }
                }
            } catch (Exception ex) {
                response.getWriter().println("File upload failed: " + ex.getMessage());
            }
        } else {
            response.getWriter().println("Request does not contain upload data");
        }
    }
}

实现文件下载

创建一个Java类（例如FileDownloadServlet.java），并实现文件下载功能：

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;

public class FileDownloadServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
    private static final String UPLOAD_DIRECTORY = "uploads";

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String fileName = request.getParameter("file");
        if (fileName == null || fileName.isEmpty()) {
            response.getWriter().println("File name is missing");
            return;
        }

        File file = new File(UPLOAD_DIRECTORY + File.separator + fileName);
        if (!file.exists()) {
            response.getWriter().println("File not found");
            return;
        }

        response.setContentType("application/octet-stream");
        response.setContentLength((int) file.length());
        response.setHeader("Content-Disposition", "attachment; filename=" + fileName);

        FileInputStream fileInputStream = new FileInputStream(file);
        OutputStream responseOutputStream = response.getOutputStream();
        byte[] buffer = new byte[4096];
        int bytesRead;

        while ((bytesRead = fileInputStream.read(buffer)) != -1) {
            responseOutputStream.write(buffer, 0, bytesRead);
        }

        fileInputStream.close();
        responseOutputStream.flush();
    }
}

配置Tomcat

编辑/etc/tomcat9/webapps/your-webapp/WEB-INF/web.xml文件，添加以下代码以配置文件下载：

<servlet>
    <servlet-name>FileDownloadServlet</servlet-name>
    <servlet-class>FileDownloadServlet</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>FileDownloadServlet</servlet-name>
    <url-pattern>/download</url-pattern>
</servlet-mapping>

现在，你可以通过访问http://your-debian-server-ip:8080/your-webapp/fileUpload.jsp来实现文件上传，通过访问http://your-debian-server-ip:8080/your-webapp/download?file=your-file-name来实现文件下载。

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