servlet文件下載

package com.carrmee.servlet;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.FileInputStream;
import java.io.IOException;

@WebServlet("/downloadServlet")
public class downloadServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request,response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//        獲取參數名
        String filename = request.getParameter("filename");
//        使用字節輸入流加載文件
//        找到文件的服務器路徑
        ServletContext servletContext = request.getServletContext();
        String realPath = servletContext.getRealPath("/img/" + filename);
//用字節流關聯
        FileInputStream fis = new FileInputStream(realPath);


        //以附件形式
        String mimeType = servletContext.getMimeType(filename);
        response.setHeader("content-type",mimeType);

        response.setHeader("content-disposition","attachment;filename="+filename);


//        將輸入流寫出到輸出流
        ServletOutputStream sos = response.getOutputStream();
        byte[] buff = new byte[1024*8];
        int len = 0;
        while ((len=fis.read(buff))!=-1){
            sos.write(buff,0,len);
        }
        fis.close();
    }
}