使用HTTP方式下载文件( 仅支持另存为)
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public class DownFile extends HttpServlet{
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
// TODO Auto-generated method stub
resp.setContentType("text/html;charset=utf-8");
resp.setCharacterEncoding("utf-8");
resp.reset();
long pos = 0;
String fileLocation = req.getParameter("fileName");
System.out.println("The file is:" + fileLocation);
String subFileName = fileLocation.substring(fileLocation.lastIndexOf("/")+1,fileLocation.length());
String fileName = new String(subFileName.getBytes("iso-8859-1"),"utf-8");
OutputStream os = null;
FileInputStream is = null;
try {
File f = new File(req.getSession().getServletContext().getRealPath("/resource/temp/down") +"/"+fileName);
is = new FileInputStream(f);
long fSize = f.length();
byte xx[] = new byte[4096];
resp.setHeader("Accept-Ranges", "bytes");
resp.setHeader("Content-Length", fSize + "");
//对名字进行编码，这一步很重要
String encoderName = URLEncoder.encode(fileName, "UTF-8");
//filename下载时显示的文件名
resp.setHeader("Content-Disposition", "attachment;filename="+encoderName);
if (req.getHeader("Range") != null) {
// 若客户端传来Range，说明之前下载了一部分，设置206状态(SC_PARTIAL_CONTENT)
resp.setStatus(HttpServletResponse.SC_PARTIAL_CONTENT);
pos = Long.parseLong(req.getHeader("Range").replaceAll("bytes=", "").replaceAll("-", ""));
}
if (pos != 0) {
String contentRange = new StringBuffer("bytes ")
.append(new Long(pos).toString()).append("-")
.append(new Long(fSize - 1).toString()).append("/")
.append(new Long(fSize).toString()).toString();
resp.setHeader("Content-Range", contentRange);
System.out.println("Content-Range=" + contentRange);
// 略过已经传输过的字节
is.skip(pos);
}
os = resp.getOutputStream();
boolean all = false;
while (!all) {
int n = is.read(xx);
if (n != -1) {
os.write(xx, 0, n);
} else {
all = true;
}
}
} catch (IOException e) {
e.printStackTrace();
return;
} finally {
if (is != null)
is.close();
if (os != null)
os.close();
}
}
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@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
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}
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}
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jsp页面
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<a href="<%=path %>/downFile?fileName=${content.filePath}">下载</a>
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以下方法也可使用
在服务器端把文件转换成输出流，写入到response，以response把文件带到浏览器，由浏览器来提示用户是否愿意保存文件到本地
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第一种：
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>
第二种方法
使用servlet 首先配置web.xml
?<servlet>
?<servlet-name>DownloadFile</servlet-name>
?<servlet-class>com.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();
//得到下载的路径
?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>
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