package?com.gx.servlet;??
??
import?java.io.File;??
import?java.io.FileInputStream;??
import?java.io.IOException;??
import?java.io.OutputStream;??
import?javax.servlet.ServletException;??
import?javax.servlet.http.HttpServlet;??
import?javax.servlet.http.HttpServletRequest;??
import?javax.servlet.http.HttpServletResponse;??

import?com.sun.org.apache.xml.internal.security.utils.base64;
??
public?class?DownloadServlet?extends?HttpServlet?{??
??
????public?void?doGet（HttpServletRequest?request?HttpServletResponse?response）??
????????????throws?ServletException?IOException?{??
????????response.setCharacterEncoding（“UTF-8“）;??
????????//獲得要下載的文件名??
????????String?fileName?=?request.getParameter（“fileName“）;??
????????//fileName?=?new?String（fileName.getBytes（“iso8859-1“）“UTF-8“）;??//如果jsp頁面編碼是iso8859-1，需要使用這個轉(zhuǎn)換亂碼
????????//上傳的文件都是保存在/upload目錄下的子目錄當(dāng)中??
????????String?fileSaveRootPath=this.getServletContext（）.getRealPath（“/upload“）;??
????????//通過文件名找出文件的所在目錄??
????????String?path?=?findFileSavePathByFileName（fileNamefileSaveRootPath）;??
????????//得到要下載的文件??
????????File?file?=?new?File（pathfileName）;??
????????System.out.println（“文件保存路徑:“+path+“\\“+fileName）;??
????????//如果文件不存在??
????????if（!file.exists（））{??
????????????request.setAttribute（“message“?“您要下載的資源已被刪除！！“）;??
????????????request.getRequestDispatcher（“/message.jsp“）.forward（request?response）;??
????????????return;??
????????}??
????????//處理文件名??
????????String?realName?=?fileName.substring（fileName.indexOf（“_“）+1）;??
?????????//設(shè)置響應(yīng)頭，控制瀏覽器下載該文件??
????????response.setHeader（“Content-Disposition“?String.format（“attachment;filename*=utf-8’zh_cn%s“java.net.URLEncoder.encode（realName“UTF-8“）））;??
????????//讀取要下載的文件，保存到文件輸入流??
????????FileInputStream?in?=?new?FileInputStream（file）;??
????????//創(chuàng)建輸出流??
????????OutputStream?out?=?response.getOutputStream（）;??
????????//創(chuàng)建緩沖區(qū)??
????????byte?buffer[]?=?new?byte[1024];??
????????int?len?=?0;??
????????//循環(huán)將輸入流中的內(nèi)容讀取到緩沖區(qū)當(dāng)中??
????????while（（len=in.read（buffer））>0）{??
?????????????//輸出緩沖區(qū)的內(nèi)容到瀏覽器，實(shí)現(xiàn)文件下載??
????????????out.write（buffer?0?len）;??
??????????}??
????????//關(guān)閉文件輸入流??
????????in.close（）;??
????????//關(guān)閉輸出流??
????????out.close（）;??
????}??
??
????public?void?doPost（HttpServletRequest?request?HttpServletResponse?response）??
????????????throws?ServletException?IOException?{??
????????doGet（request?response）;??
????}??
??
????????/**?
????????*?@Method:?findFileSavePathByFileName?
????????*?@Description:?通過文件名和存儲上傳文件根目錄找出要下載的文件的所在路徑?
????????*?@param?filename?要下載的文件名?
????????*?@param?saveRootPath?上傳文件保存的根目錄，也就是/upload目錄?
????????*?@return?要下載的文件的存儲目錄?
????????*/???
????????public?String?findFileSavePathByFileName（String?filenameString?saveRootPath）{??
????????????int?hashcode?=?filename.hashCode（）;??
????????????int?dir1?=?hashcode&0xf;??//0--15??
????????????int?dir2?=?（hashcode&0xf0）>>4;??//0-15??
????????????String?dir?=?saveRootPath?+?“\\“?+?dir1?+?“\\“?+?dir

?屬性????????????大小?????日期????時間???名稱
-----------?---------??----------?-----??----
?????目錄???????????0??2018-01-06?11:24??文件上傳下載\
?????目錄???????????0??2018-01-06?11:24??文件上傳下載\FileUpDownLoad\
?????文件?????????529??2018-01-06?10:25??文件上傳下載\FileUpDownLoad\.classpath
?????目錄???????????0??2018-01-06?10:25??文件上傳下載\FileUpDownLoad\.myeclipse\
?????文件?????????315??2018-01-06?10:25??文件上傳下載\FileUpDownLoad\.mymetadata
?????文件????????1757??2018-01-06?10:29??文件上傳下載\FileUpDownLoad\.project
?????目錄???????????0??2018-01-06?11:24??文件上傳下載\FileUpDownLoad\.settings\
?????文件?????????500??2018-01-06?10:25??文件上傳下載\FileUpDownLoad\.settings\.jsdtscope
?????文件?????????364??2018-01-06?10:25??文件上傳下載\FileUpDownLoad\.settings\org.eclipse.jdt.core.prefs
?????文件?????????480??2018-01-06?10:25??文件上傳下載\FileUpDownLoad\.settings\org.eclipse.wst.common.component
?????文件?????????252??2018-01-06?10:25??文件上傳下載\FileUpDownLoad\.settings\org.eclipse.wst.common.project.facet.core.xml
?????文件??????????49??2018-01-06?10:25??文件上傳下載\FileUpDownLoad\.settings\org.eclipse.wst.jsdt.ui.superType.container
?????文件???????????6??2018-01-06?10:25??文件上傳下載\FileUpDownLoad\.settings\org.eclipse.wst.jsdt.ui.superType.name
?????目錄???????????0??2018-01-06?10:27??文件上傳下載\FileUpDownLoad\src\
?????目錄???????????0??2018-01-06?10:27??文件上傳下載\FileUpDownLoad\src\com\
?????目錄???????????0??2018-01-06?10:27??文件上傳下載\FileUpDownLoad\src\com\gx\
?????目錄???????????0??2018-01-06?11:24??文件上傳下載\FileUpDownLoad\src\com\gx\servlet\
?????文件????????3743??2018-01-06?10:48??文件上傳下載\FileUpDownLoad\src\com\gx\servlet\DownloadServlet.java
?????文件????????7312??2018-01-06?10:40??文件上傳下載\FileUpDownLoad\src\com\gx\servlet\UploadServlet.java
?????目錄???????????0??2018-01-06?11:24??文件上傳下載\FileUpDownLoad\WebRoot\
?????文件?????????551??2018-01-06?10:43??文件上傳下載\FileUpDownLoad\WebRoot\download.jsp
?????文件?????????359??2018-01-06?10:41??文件上傳下載\FileUpDownLoad\WebRoot\message.jsp
?????目錄???????????0??2018-01-06?10:25??文件上傳下載\FileUpDownLoad\WebRoot\meta-INF\
?????文件??????????36??2018-01-06?10:25??文件上傳下載\FileUpDownLoad\WebRoot\meta-INF\MANIFEST.MF
?????文件?????????946??2018-01-06?10:42??文件上傳下載\FileUpDownLoad\WebRoot\upload.jsp
?????目錄???????????0??2018-01-06?11:24??文件上傳下載\FileUpDownLoad\WebRoot\WEB-INF\
?????目錄???????????0??2018-01-06?10:27??文件上傳下載\FileUpDownLoad\WebRoot\WEB-INF\classes\
?????目錄???????????0??2018-01-06?10:27??文件上傳下載\FileUpDownLoad\WebRoot\WEB-INF\classes\com\
?????目錄???????????0??2018-01-06?10:27??文件上傳下載\FileUpDownLoad\WebRoot\WEB-INF\classes\com\gx\
?????目錄???????????0??2018-01-06?11:24??文件上傳下載\FileUpDownLoad\WebRoot\WEB-INF\classes\com\gx\servlet\
?????文件????????3724??2018-01-06?10:48??文件上傳下載\FileUpDownLoad\WebRoot\WEB-INF\classes\com\gx\servlet\DownloadServlet.class
............此處省略6個文件信息