实现文件下载 Servlet
实现文件下载 Servlet 允许用户从 Web 应用程序检索文件。
如何实现文件下载:
要启用文件下载,我们可以创建一个 servlet 作为下载端点,并将其映射到 web.xml 中的特定 URL。
示例Servlet:
DownloadServlet.java
import java.io.*; import javax.servlet.*; import javax.servlet.http.*; public class DownloadServlet extends HttpServlet { protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // Get the file ID from the request String id = request.getParameter("id"); // Fetch file metadata from the database String fileName = ""; String fileType = ""; // Set the response content type based on file type response.setContentType(fileType); // Set the content disposition header to prompt download response.setHeader("Content-disposition", "attachment; filename=yourcustomfilename.pdf"); // Create a File object using the file path File file = new File(fileName); // Stream the file to the client InputStream in = new FileInputStream(file); OutputStream out = response.getOutputStream(); // Copy file content in chunks byte[] buffer = new byte[4096]; int length = 0; while ((length = in.read(buffer)) > 0) { out.write(buffer, 0, length); } in.close(); out.flush(); } }
在 servlet 的 doGet 方法中,我们:
web.xml 中的映射:
<servlet> <servlet-name>DownloadServlet</servlet-name> <servlet-class>com.myapp.servlet.DownloadServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>DownloadServlet</servlet-name> <url-pattern>/download</url-pattern> </servlet-mapping>
此设置允许用户通过发送 GET 请求来下载文件到 /download?id=
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