1、文件下载有两种方式:一种是超链接,一种是Servlet提供下载。
2、超链接下载时:当文件可以在网页直接打开时,会直接打开文件,而不是下载,当文件打开不了时,会提供下载窗口。
3、超链接下载原理
4、Servlet下载文件的原理
5、代码示例
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import java.io.FileInputStream; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.net.URLEncoder; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class DownloadServlet extends HttpServlet { protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request, response); } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String filename = request.getParameter("filename"); //1 获取要下载的文件名 // 2 把文件所在的文件夹相对路径转成绝对路径 String folderPath = this.getServletContext().getRealPath("download"); // 3获得输入流用来将服务器上的文件读出 InputStream is = new FileInputStream(folderPath+"/"+filename); // 4向相应的头部添加信息,作用是用来弹出保存文件的对话框 //response.setHeader("Content-Disposition", "attachment;filename="+filename); // 中文文件名下载对话框中将是乱码。处理方式:IE浏览器和其他浏览器的处理方式不同 //IE: //response.setHeader("Content-Disposition", "attachment;filename="+URLEncoder.encode(filename, "UTF-8")); //FireFox String newFilename = new String(filename.getBytes("UTF-8"),"iso-8859-1"); response.setHeader("Content-Disposition", "attachment;filename="+newFilename); // 5写到本地磁盘上 OutputStream os = response.getOutputStream(); int len=0; byte[] b = new byte[1024]; while((len=is.read(b))!=-1){ os.write(b,0, len); } is.close(); os.close(); } }