1、專案結構

程式碼：

package com.guangtao.servlet;

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.FileInputStream;
import java.io.IOException;

 
public class FileServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 1、獲取要下載的檔案
        String realPath = "D:\\Java_File\\javaweb-maven-servlet\\response\\src\\main\\resources\\廣濤.png";
        System.out.println(
 
"要下載的路徑： " + realPath);
        // 2、下載的檔案命名是啥？   擷取到最後的\   索引加1
        String filename = realPath.substring(realPath.lastIndexOf("\\") + 1);
        System.out.println(filename);   // 廣濤.png
        // 3、加入支援瀏覽器下載的請求頭
        resp.setHeader("Content-disposition", "attachment;filename" + filename);
        
 
// 4、獲取下載檔案的輸入流
        FileInputStream in = new FileInputStream(realPath);
        // 5、建立緩衝區
        int len = 0;
        byte[] buffer = new byte[1024];
        // 6、獲取OutputStream 物件
        ServletOutputStream out = resp.getOutputStream();
        // 7、將FileOutputStream 流寫入到buffer緩衝區，使用OutputStream將緩衝區中的資料輸出到客戶端
        while ((len = in.read(buffer)) > 0) {
            out.write(buffer, 0, len);
        }
        // 關閉資源
        in.close();
        out.close();
    }
    
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}