Servlet實現基本檔案上傳

 

實現檔案上傳，表單屬性需要設定為method=”post”，encType=multipart/form-data，在伺服器端通過request.getInputStream()獲得檔案輸入資料流，然後對流進行操作，獲得所需要的內容。

 

 

Html頁面代碼upload.html

<form action="UploadServlet3" method="post" enctype="multipart/form-data">    <input type="file" name="file">    <input type="submit" name="upload"value="上傳"></form>

1.實現基本檔案上傳

Servlet代碼

public class UploadServlet1 extends HttpServlet {    private static final long serialVersionUID = 1L;    protected void doPost(HttpServletRequest request, HttpServletResponseresponse) throws ServletException, IOException {           InputStream in = request.getInputStream();           File f = new File("d:/temp","aaa.txt");           FileOutputStream fos = new FileOutputStream(f);           byte[] b = new byte[1024];           int n=0;           while((n=in.read(b))!=-1){              fos.write(b,0,n);           }           fos.close();           in.close();    }}

此方法上傳的檔案開啟後如下：

-----------------------------26962244645705

Content-Disposition: form-data; name="file";filename="a.txt"

Content-Type: text/plain

 

Java Servlet Technology

As soon as the web began to be used for deliveringservices, service providers recognized the need for dynamic content. Applets,one of the earliest attempts toward this goal, focused on using the clientplatform to deliver dynamic user experiences. At the same time, developers alsoinvestigated using the server platform for this purpose. Initially, CommonGateway Interface (CGI) scripts were the main technology used to generatedynamic content. Although widely used, CGI scripting technology has a number ofshortcomings, including platform dependence and lack of scalability. To addressthese limitations, Java Servlet technology was created as a portable way toprovide dynamic, user-oriented content.

-----------------------------26962244645705

Content-Disposition: form-data; name="upload"

 

上傳

-----------------------------26962244645705--

此處有一個斷行符號符

前面4行和後面6行是表單的一些屬性，是預設加入的。

 

2.出去檔案流中的多餘內容（只支援ie）

UploadServlet2

public class UploadServlet2 extends HttpServlet {private static final long serialVersionUID = 1L;protected void doPost(HttpServletRequest request,HttpServletResponse response) throws ServletException, IOException {String tempFileName = (String) request.getSession().getId();// create the tempfile.File temp = new File("d:/temp", tempFileName);FileOutputStream o = new FileOutputStream(temp);if (request.getContentLength() > 297) {// write theupload content to the temp file.InputStream in = request.getInputStream();byte b[] = new byte[1024];int n;while ((n = in.read(b)) != -1) {o.write(b, 0, n);}o.close();in.close();// read the tempfile.RandomAccessFile random = new RandomAccessFile(temp, "r");// read Line2 tofind the name of the upload file.int second = 1;String secondLine = null;while (second <= 2) {secondLine = random.readLine();second++;}// get the lastlocation of the dir char.'\\'.int position = secondLine.lastIndexOf('\\');// get the nameof the upload file.String fileName = secondLine.substring(position + 1,secondLine.length() - 1);// relocate tothe head of file.random.seek(0);// get thelocation of the char.'Enter' in Line4.long forthEndPosition = 0;int forth = 1;while ((n = random.readByte()) != -1 && (forth <= 4)) {if (n == '\n') {forthEndPosition = random.getFilePointer();forth++;}}File realFile = new File("d:/temp", fileName);RandomAccessFile random2 = new RandomAccessFile(realFile, "rw");// locate the endposition of the content.Count backwards 6 lines.random.seek(random.length());long endPosition = random.getFilePointer();long mark = endPosition;int j = 1;while ((mark >= 0) && (j <= 6)) {mark--;random.seek(mark);n = random.readByte();if (n == '\n') {endPosition = random.getFilePointer();j++;}}// locate to thebegin of content.Count for 4 lines's end position.random.seek(forthEndPosition);long startPoint = random.getFilePointer();// read the realcontent and write it to the realFile.while (startPoint < endPosition - 1) {n = random.readByte();random2.write(n);startPoint = random.getFilePointer();}random2.close();random.close();// delete the tempfile.temp.delete();System.out.println("File uploadsuccess!");} else {System.out.println("Nofile!");}}}