Debian上JSP如何实现文件上传下载 - 问答

在Debian系统上，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开发环境。如果没有，请运行以下命令安装：

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

安装Tomcat服务器

在Debian上安装Tomcat服务器，可以使用以下命令：

sudo apt-get install tomcat9

配置Tomcat

编辑Tomcat的配置文件/etc/tomcat9/server.xml，在<Host>标签内添加以下内容：

<Resource name="file" auth="Container" type="java.io.File" description="File Upload" driverClassName="org.apache.tomcat.jdbc.pool.DataSource" url="jdbc:h2:mem:testdb" username="sa" password="" maxActive="20" maxIdle="10" maxWait="-1"/>

创建JSP文件

在Tomcat的webapps目录下创建一个名为file_upload_download.jsp的文件，然后添加以下内容：

<%@ page import="java.io.*, java.util.*, javax.servlet.*, javax.servlet.http.*, javax.servlet.annotation.*, org.apache.commons.fileupload.*, org.apache.commons.fileupload.disk.*, org.apache.commons.io.*" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<!DOCTYPE html>
<html>
<head>
    <title>File Upload and Download</title>
</head>
<body>
<%
    String uploadPath = application.getRealPath("") + "uploads";
    File fileSaveDir = new File(uploadPath);
    if (!fileSaveDir.exists()) {
        fileSaveDir.mkdir();
    }
    if (request.getMethod().equalsIgnoreCase("POST")) {
        try {
            Class.forName("org.apache.commons.fileupload.servlet.ServletFileUpload");
            ServletFileUpload upload = new ServletFileUpload();
            List<FileItem> formItems = upload.parseRequest(request);
            if (formItems != null && formItems.size() > 0) {
                for (FileItem item : formItems) {
                    if (!item.isFormField()) {
                        String fileName = new File(item.getName()).getName();
                        String filePath = uploadPath + File.separator + fileName;
                        File storeFile = new File(filePath);
                        item.write(storeFile);
                        out.println("File " + fileName + " has uploaded successfully!");
                    }
                }
            }
        } catch (Exception ex) {
            out.println("There was an error: " + ex.getMessage());
        }
    }
%>
<form action="file_upload_download.jsp" method="post" enctype="multipart/form-data">
    <input type="file" name="file" />
    <input type="submit" value="Upload" />
</form>
<%
    String downloadFileName = request.getParameter("download");
    if (downloadFileName != null && !downloadFileName.isEmpty()) {
        String filePath = uploadPath + File.separator + downloadFileName;
        File fileToDownload = new File(filePath);
        if (fileToDownload.exists()) {
            response.setContentType("application/octet-stream");
            response.setHeader("Content-Disposition", "attachment;filename=" + downloadFileName);
            FileInputStream inStream = new FileInputStream(fileToDownload);
            OutputStream outStream = response.getOutputStream();
            byte[] buffer = new byte[4096];
            int length;
            while ((length = inStream.read(buffer)) > 0) {
                outStream.write(buffer, 0, length);
            }
            inStream.close();
            outStream.flush();
        }
    }
%>
</body>
</html>

重启Tomcat服务器

保存文件后，重启Tomcat服务器以使更改生效：

sudo systemctl restart tomcat9

现在，你可以访问http://your_server_ip:8080/file_upload_download.jsp来测试文件上传和下载功能。请注意，这个示例使用了Apache Commons FileUpload库，你可能需要将其添加到项目的依赖中。

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