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>> 如何在Web页上实现文件上传 [<a href=http://www.jsp001.com/forum/showthread.php?goto=newpost&threadid=107>查看别人的评论</a>]<br>
<hr><p>由 webmaster 发布于: 2001-01-21 11:08</p><p> </p><p><br>public class UploadServlet extends HttpServlet<br>{<br> //default maximum allowable file size is 100k<br> static final int MAX_SIZE = 102400;<br> //instance variables to store root and success message<br> String rootPath, successMessage;<br> /**<br> * init method is called when servlet is initialized.<br> */<br> public void init(ServletConfig config) throws ServletException<br> {<br> super.init(config);<br> //get path in which to save file<br> rootPath = config.getInitParameter("RootPath");<br> if (rootPath == null)<br> {<br> rootPath = "/";<br> }<br> /*Get message to show when upload is complete. Used only if<br> a success redirect page is not supplied.*/<br> successMessage = config.getInitParameter("SuccessMessage");<br> if (successMessage == null)<br> {<br> successMessage = "File upload complete!";<br> }<br> }<br> /**<br> * doPost reads the uploaded data from the request and writes<br> * it to a file.<br> */<br> public void doPost(HttpServletRequest request,<br> HttpServletResponse response)<br> {<br> ServletOutputStream out=null;<br> DataInputStream in=null;<br> FileOutputStream fileOut=null;<br> try<br> {<br> /*set content type of response and get handle to output<br> stream in case we are unable to redirect client*/<br> response.setContentType("text/plain");<br> out = response.getOutputStream();<br> }<br> catch (IOException e)<br> {<br> //print error message to standard out<br> System.out.println("Error getting output stream.");<br> System.out.println("Error description: " + e);<br> return;<br> }<br> try<br> {<br> //get content type of client request<br> String contentType = request.getContentType();<br> //make sure content type is multipart/form-data<br> if(contentType != null && contentType.indexOf(<br> "multipart/form-data") != -1)<br> {<br> //open input stream from client to capture upload file<br> in = new DataInputStream(request.getInputStream());<br> //get length of content data<br> int formDataLength = request.getContentLength();<br> //allocate a byte array to store content data<br> byte dataBytes[] = new byte[formDataLength];<br> //read file into byte array<br> int bytesRead = 0;<br> int totalBytesRead = 0;<br> int sizeCheck = 0;<br> while (totalBytesRead < formDataLength)<br> {<br> //check for maximum file size violation<br> sizeCheck = totalBytesRead + in.available();<br> if (sizeCheck > MAX_SIZE)<br> {<br> out.println("Sorry, file is too large to upload.");<br> return;<br> }<br> bytesRead = in.read(dataBytes, totalBytesRead,<br> formDataLength);<br> totalBytesRead += bytesRead;<br> }<br> //create string from byte array for easy manipulation<br> String file = new String(dataBytes);<br> //since byte array is stored in string, release memory<br> dataBytes = null;<br> /*get boundary value (boundary is a unique string that<br> separates content data)*/<br> int lastIndex = contentType.lastIndexOf("=");<br> String boundary = contentType.substring(lastIndex+1,<br> contentType.length());<br> //get Directory web variable from request<br> String directory="";<br> if (file.indexOf("name=\"Directory\"") > 0)<br> {<br> directory = file.substring(<br> file.indexOf("name=\"Directory\""));<br> //remove carriage return<br> directory = directory.substring(<br> directory.indexOf("\n")+1);<br> //remove carriage return<br> directory = directory.substring(<br> directory.indexOf("\n")+1);<br> //get Directory<br> directory = directory.substring(0,<br> directory.indexOf("\n")-1);<br> /*make sure user didn't select a directory higher in<br> the directory tree*/<br> if (directory.indexOf("..") > 0)<br> {<br> out.println("Security Error: You can't upload " +<br> "to a directory higher in the directory tree.");<br> return;<br> }<br> }<br> //get SuccessPage web variable from request<br> String successPage="";<br> if (file.indexOf("name=\"SuccessPage\"") > 0)<br> {<br> successPage = file.substring(<br> file.indexOf("name=\"SuccessPage\""));<br> //remove carriage return<br> successPage = successPage.substring(<br> successPage.indexOf("\n")+1);<br> //remove carriage return<br> successPage = successPage.substring(<br> successPage.indexOf("\n")+1);<br> //get success page<br> successPage = successPage.substring(0,<br> successPage.indexOf("\n")-1);<br> }<br> //get OverWrite flag web variable from request<br> String overWrite;<br> if (file.indexOf("name=\"OverWrite\"") > 0)<br> {<br> overWrite = file.substring(<br> file.indexOf("name=\"OverWrite\""));<br> //remove carriage return<br> overWrite = overWrite.substring(<br> overWrite.indexOf("\n")+1);<br> //remove carriage return<br> overWrite = overWrite.substring(<br> overWrite.indexOf("\n")+1);<br> //get overwrite flag<br> overWrite = overWrite.substring(0,<br> overWrite.indexOf("\n")-1);<br> }<br> else<br> {<br> overWrite = "false";<br> }<br> //get OverWritePage web variable from request<br> String overWritePage="";<br> if (file.indexOf("name=\"OverWritePage\"") > 0)<br> {<br> overWritePage = file.substring(<br> file.indexOf("name=\"OverWritePage\""));<br> //remove carriage return<br> overWritePage = overWritePage.substring(<br> overWritePage.indexOf("\n")+1);<br> //remove carriage return<br> overWritePage = overWritePage.substring(<br> overWritePage.indexOf("\n")+1);<br> //get overwrite page<br> overWritePage = overWritePage.substring(0,<br> overWritePage.indexOf("\n")-1);<br> }<br> //get filename of upload file<br> String saveFile = file.substring(<br> file.indexOf("filename=\"")+10);<br> saveFile = saveFile.substring(0,<br> saveFile.indexOf("\n"));<br> saveFile = saveFile.substring(<br> saveFile.lastIndexOf("\\")+1,<br> saveFile.indexOf("\""));<br> /*remove boundary markers and other multipart/form-data<br> tags from beginning of upload file section*/<br> int pos; //position in upload file<br> //find position of upload file section of request<br> pos = file.indexOf("filename=\"");<br> //find position of content-disposition line<br> pos = file.indexOf("\n",pos)+1;<br> //find position of content-type line<br> pos = file.indexOf("\n",pos)+1;<br> //find position of blank line<br> pos = file.indexOf("\n",pos)+1;<br> /*find the location of the next boundary marker<br> (marking the end of the upload file data)*/<br> int boundaryLocation = file.indexOf(boundary,pos)-4;<br> //upload file lies between pos and boundaryLocation<br> file = file.substring(pos,boundaryLocation);<br> //build the full path of the upload file<br> String fileName = new String(rootPath + directory +<br> saveFile);<br> //create File object to check for existence of file<br> File checkFile = new File(fileName);<br> if (checkFile.exists())<br> {<br> /*file exists, if OverWrite flag is off, give<br> message and abort*/<br> if (!overWrite.toLowerCase().equals("true"))<br> {<br> if (overWritePage.equals(""))<br> {<br> /*OverWrite HTML page URL not received, respond<br> with generic message*/<br> out.println("Sorry, file already exists.");<br> }<br> else<br> {<br> //redirect client to OverWrite HTML page<br> response.sendRedirect(overWritePage);<br> }<br> return;<br> }<br> }<br> /*create File object to check for existence of<br> Directory*/<br> File fileDir = new File(rootPath + directory);<br> if (!fileDir.exists())<br> {<br> //Directory doesn't exist, create it<br> fileDir.mkdirs();<br> }<br> //instantiate file output stream<br> fileOut = new FileOutputStream(fileName);<br> //write the string to the file as a byte array<br> fileOut.write(file.getBytes(),0,file.length());<br> if (successPage.equals(""))<br> {<br> /*success HTML page URL not received, respond with<br> generic success message*/<br> out.println(successMessage);<br> out.println("File written to: " + fileName);<br> }<br> else<br> {<br> //redirect client to success HTML page<br> response.sendRedirect(successPage);<br> }<br> }<br> else //request is not multipart/form-data<br> {<br> //send error message to client<br> out.println("Request not multipart/form-data.");<br> }<br> }<br> catch(Exception e)<br> {<br> try<br> {<br> //print error message to standard out<br> System.out.println("Error in doPost: " + e);<br> //send error message to client<br> out.println("An unexpected error has occurred.");<br> out.println("Error description: " + e);<br> }<br> catch (Exception f) {}<br> }<br> finally<br> {<br> try<br> {<br> fileOut.close(); //close file output stream<br> }<br> catch (Exception f) {}<br> try<br> {<br> in.close(); //close input stream from client<br> }<br> catch (Exception f) {}<br> try<br> {<br> out.close(); //close output stream to client<br> }<br> catch (Exception f) {}<br> }<br> }<br>}<br><br></p></td>
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