我应该如何实现简单的文件下载servlet?
这个想法是通过 GET 请求index.jsp?filename=file.txt
,用户可以下载例如。file.txt
来自文件 servlet,文件 servlet 会将该文件上传给用户。
我可以获取到文件,但是如何实现文件下载呢?
假设您可以访问 servlet,如下所示
http://localhost:8080/myapp/download?id=7
我需要创建一个 servlet 并将其注册到 web.xml
web.xml
<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>
下载Servlet.java
public class DownloadServlet extends HttpServlet {
protected void doGet( HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String id = request.getParameter("id");
String fileName = "";
String fileType = "";
// Find this file id in database to get file name, and file type
// You must tell the browser the file type you are going to send
// for example application/pdf, text/plain, text/html, image/jpg
response.setContentType(fileType);
// Make sure to show the download dialog
response.setHeader("Content-disposition","attachment; filename=yourcustomfilename.pdf");
// Assume file name is retrieved from database
// For example D:\\file\\test.pdf
File my_file = new File(fileName);
// This should send the file to browser
OutputStream out = response.getOutputStream();
FileInputStream in = new FileInputStream(my_file);
byte[] buffer = new byte[4096];
int length;
while ((length = in.read(buffer)) > 0){
out.write(buffer, 0, length);
}
in.close();
out.flush();
}
}
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