文件下载

在实现文件下载时，我们需要在响应头中添加附加信息
response.addHeader(“Content-Disposition”, “attachment; filename=”+文件名);
Content-Disposition:attachment
该附加信息表示作为对下载文件的一个标识字段。不会在浏览器中显示而是直接做下载处理。
filename=文件名
表示指定下载文件的文件名

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.*;
public class FileDownLoadServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doPost(req, resp);
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //读取下载文件
        File file = new File("D:\\DownloadFile/rog.jpg");
        InputStream inputStream = new FileInputStream(file);
        byte[] buff = new byte[inputStream.available()];
        inputStream.read(buff);
        //在响应中添加附加信息
        resp.addHeader("Content-Disposition","attachment;filename="+file.getName());
        //产生响应
        OutputStream outputStream = resp.getOutputStream();
        outputStream.write(buff);
        outputStream.flush();
        outputStream.close();
        inputStream.close();
    }
}