Servlet文件下载实现

Servlet文件下载实现

思路

下载文件的前提：我们需要一个文件(二进制IO流)和下载后的文件名

此时，我们知道使用resp可以向浏览器输出打印流（resp.getWriter().print()）

那么我们让resp向浏览器输出二进制流就行了

获取OutputStream对象

ServletOutputStream os = resp.getOutputStream();

设置能支持浏览器下载的头信息: resp.setHeader("Content-Disposition", "attachment; filename="+fileName);

代码实现

package com.base.index01;

import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.FileInputStream;
import java.io.IOException;

public class FileServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 获取文件的绝对地址
        String realPath = "D:\\MYcode_K\\Servlet_K\\Demo1\\response\\src\\main\\resources\\1.png";
        // 通过切割字符串获取文件名
        String fileName = realPath.substring(realPath.lastIndexOf("\\") + 1);
        // 设置能支持浏览器下载的头信息
        resp.setHeader("Content-Disposition", "attachment; filename="+fileName);
        // 获取下载文件的文件流
        FileInputStream is = new FileInputStream(realPath);

        // 获取OutputStream对象
        ServletOutputStream os = resp.getOutputStream();
        // 创建缓冲区
        BufferedInputStream bufferedInputStream = new BufferedInputStream(is);
        BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(os);

        // 读写操作
        int len = 0;
        byte[] bytes = new byte[1024];

        while ((len = bufferedInputStream.read(bytes)) > 0) {
            bufferedOutputStream.write(bytes,0,len);
        }
        // 释放资源
        bufferedOutputStream.close();
        bufferedInputStream.close();
        os.close();
        is.close();
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}