引用：
第一种：
就是直接给出下载的地址，这种方式很不好，因为会暴露你的地址，带来很多不安全的因素，可以说是千万不要用这种
第二种：
下载页面
<%@ page language="java" import="java.util.*" pageEncoding="GB18030"%>
<html><head> <title>download</title></head>
<body><a href="xia.jsp?filename=新建文档.txt">新建文档.txt</a></body></html>然后编写如下页面
<%@ page contentType="text/html;charset=gbk"%>
<%@ page language="java" import="java.io.*,java.net.*" pageEncoding="gbk"%><html><head> <title>test</title></head>
<body><% response.setContentType("text/html");javax.servlet.ServletOutputStream ou = response.getOutputStream();String filepath="uploadfile/";String filename=new String(request.getParameter("filename").getBytes("ISO8859_1"),"GB2312").toString();System.out.println("DownloadFile filepath:" + filepath);System.out.println("DownloadFile filename:" + filename);java.io.File file = new java.io.File(filepath + filename);if (!file.exists()) { System.out.println(file.getAbsolutePath() + " 文件不存在!");return;}// 读取文件流java.io.FileInputStream fileInputStream = new java.io.FileInputStream(file);// 下载文件// 设置响应头和下载保存的文件名if (filename != null && filename.length() > 0) { response.setContentType("application/x-msdownload");response.setHeader("Content-Disposition", "attachment; filename=" + new String(filename.getBytes("gb2312"),"iso8859-1") + "");if (fileInputStream != null) { int filelen = fileInputStream.available();//文件太大时内存不能一次读出,要循环byte a[] = new byte[filelen];fileInputStream.read(a);ou.write(a);}fileInputStream.close();ou.close();}%> </body></html>第三种方法
使用servlet 首先配置web.xml
<servlet>
<servlet-name>DownloadFile</servlet-name><servlet-class>libin123.com.cn.servlet.DownloadFile</servlet-class></servlet><servlet-mapping>
<servlet-name>DownloadFile</servlet-name><url-pattern>/downloadfile</url-pattern></servlet-mapping>编写DownloadFile.java类
package libin123.com.cn.servlet;
import java.io.IOException;
import java.io.PrintWriter;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import com.sun.image.codec.jpeg.ImageFormatException;import com.sun.image.codec.jpeg.JPEGCodec;import com.sun.image.codec.jpeg.JPEGImageDecoder;public class DownloadFile extends HttpServlet {
private static final long serialVersionUID = 1L;
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text/html");javax.servlet.ServletOutputStream out = response.getOutputStream();String filepath=request.getRealPath("/") + "uploadfile/";String filename=new String(request.getParameter("filename").getBytes("ISO8859_1"),"GB2312").toString();System.out.println("DownloadFile filepath:" + filepath);System.out.println("DownloadFile filename:" + filename);java.io.File file = new java.io.File(filepath + filename);if (!file.exists()) { System.out.println(file.getAbsolutePath() + " 文件不存在!");return;}// 读取文件流java.io.FileInputStream fileInputStream = new java.io.FileInputStream(file);// 下载文件// 设置响应头和下载保存的文件名if (filename != null && filename.length() > 0) { response.setContentType("application/x-msdownload");response.setHeader("Content-Disposition", "attachment; filename=" + new String(filename.getBytes("gb2312"),"iso8859-1") + "");if (fileInputStream != null) { int filelen = fileInputStream.available();//文件太大时内存不能一次读出,要循环byte a[] = new byte[filelen];fileInputStream.read(a);out.write(a);}fileInputStream.close();out.close();}}public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text/html");PrintWriter out = response.getWriter();out.println("<!DOCTYPE HTML PUBLIC -//W3C//DTD HTML 4.01 Transitional//EN>");out.println("<HTML>");out.println(" <HEAD><TITLE>A Servlet</TITLE></HEAD>");out.println(" <BODY>");out.print(" This is ");out.print(this.getClass().getName());out.println(", using the POST method");out.println(" </BODY>");out.println("</HTML>");out.flush();out.close();} }下载页面
<%@ page language="java" import="java.util.*" pageEncoding="GB18030"%>
<html><head></head>
<body><a href="downloadfile?filename=新建文档.txt">新建文档.txt</a></body></html>