前言:
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我们要下载图片首先是因为服务器里面有这张图片,我们是去请求服务器下载图片的
<!DOCTYPE html><html><head><meta charset="UTF-8"><title>Insert title here</title></head><body><a href="/Project3/img/1.jpg">图片</a><hr><a href="/Project3/DownloadServlet?filename=1.jpg">图片</a></body></html>
package cn.itcast.web.download;import java.io.FileInputStream;import java.io.IOException;import javax.servlet.ServletContext;import javax.servlet.ServletException;import javax.servlet.annotation.WebServlet;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;/** * Servlet implementation class DownloadServlet */@WebServlet("/DownloadServlet")public class DownloadServlet extends HttpServlet { private static final long serialVersionUID = 1L; /** * @see HttpServlet#HttpServlet() */ public DownloadServlet() { super(); // TODO Auto-generated constructor stub } /** * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response) */ protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //1.获取请求参数,文件名称 String filename = request.getParameter("filename"); //2.使用字节输入流加载文件进内存 //2.1找到文件服务器路径 ServletContext servletContext = this.getServletContext(); String realPath = servletContext.getRealPath("/img/"+filename); //2.2用字节流关联 FileInputStream fis=new FileInputStream(realPath);//将图片读进内存 //3.设置response的响应头 //3.1设置响应头类型:content-type String mimeType = servletContext.getMimeType(filename);//获取文件的mime类型 response.setHeader("content-type", mimeType); //3.2设置响应头的打开方式 response.setHeader("content-disposition", "attachment;filename="+filename); //4.将输入流的数据写出到输出流中 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(); } /** * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response) */ protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // TODO Auto-generated method stub doGet(request, response); }}
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