Ubuntu上JSP如何实现文件上传下载 - 问答

在Ubuntu上使用JSP实现文件上传和下载，你需要遵循以下步骤：

安装必要的软件和库

确保你已经安装了Java、Tomcat、JSP和Servlet。如果没有，请按照以下命令安装：

sudo apt update
sudo apt install openjdk-11-jdk
sudo apt install tomcat9
sudo apt install tomcat9-admin

创建一个Web应用程序

在/var/lib/tomcat9/webapps目录下创建一个新的文件夹，例如fileUploadDownload。在此文件夹中，创建一个名为WEB-INF的文件夹。在WEB-INF文件夹中，创建一个名为web.xml的文件，用于配置Servlet。

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
                             http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
         version="3.1">
    <servlet>
        <servlet-name>FileUploadServlet</servlet-name>
        <servlet-class>com.example.FileUploadServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>FileUploadServlet</servlet-name>
        <url-pattern>/upload</url-pattern>
    </servlet-mapping>
</web-app>

创建文件上传和下载的JSP页面

在fileUploadDownload文件夹中创建一个名为index.jsp的文件，用于显示文件上传表单：

<!DOCTYPE html>
<html>
<head>
    <title>File Upload and Download</title>
</head>
<body>
    <h1>Upload File</h1>
    <form action="upload" method="post" enctype="multipart/form-data">
        <input type="file" name="file" required>
        <input type="submit" value="Upload">
    </form>
</body>
</html>

实现文件上传和下载的Servlet

在fileUploadDownload文件夹中创建一个名为FileUploadServlet.java的文件，用于处理文件上传和下载请求：

package com.example;

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

@WebServlet(name = "FileUploadServlet", urlPatterns = {"/upload"})
public class FileUploadServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
    private static final String UPLOAD_DIRECTORY = "uploads";

    @Override
    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");
        }
    }

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String fileName = request.getParameter("fileName");
        if (fileName == null || fileName.isEmpty()) {
            response.getWriter().println("No file name provided");
            return;
        }

        String filePath = UPLOAD_DIRECTORY + File.separator + fileName;
        File file = new File(filePath);
        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();
    }
}

部署Web应用程序

将fileUploadDownload文件夹复制到/var/lib/tomcat9/webapps目录下。Tomcat将自动部署应用程序。

访问Web应用程序

在浏览器中访问http://your_server_ip:8080/fileUploadDownload/index.jsp，你应该能看到文件上传表单。上传文件后，可以通过访问http://your_server_ip:8080/fileUploadDownload/download?fileName=your_file_name来下载文件。

注意：这个示例使用了Apache Commons FileUpload库来处理文件上传。要将其添加到项目中，请下载jar文件并将其放入WEB-INF/lib目录下。

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