java语言下载文件 java文件下载如何实现

 

public class DownServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1.要获取下载文件的路径
        String realPath = "F:\\JavaWeb\\1.png";
        System.out.println("下载文件的路径："+realPath);
        //2.下载的文件名
        String fileName = realPath.substring(realPath.lastIndexOf("\\") + 1);
        //3.设置让浏览器能够支持（content-disposition）下载我们需要的东西。中文文件名URLEncoder.encode编码，否则可能乱码
        resp.setHeader("Content-Disposition","attachment;filename="+ URLEncoder.encode(fileName,"UTF-8"));
        //4.获取下载文件的输入流
        FileInputStream in = new FileInputStream(realPath);
        //5.获取缓冲流
        int len = 0;
        byte[] bytes = new byte[1024];
        //6.获取OutputStream对象
        ServletOutputStream out = resp.getOutputStream();
        //7.将FileOutStream 流写入到buffer缓冲区，使用OutputStream将缓冲区中的数据输出到客户端！
        while((len=in.read(bytes))>0){
            out.write(bytes,0,len);
        }
        in.close();
        out.close();
    }
}