上传pdf文件
我想使用下面给出的代码上传 pdf 文件。它提供浏览功能，但不上传文件。当我单击 sendfile 按钮时，它显示 uploadfile.html 代码页。我怎样才能做到这一点？？？ 给定代码中的错误在哪里？？？
文件名-upload.html
<%@ page language="java" %>
<HTml>
<HEAD><TITLE>Display file upload form to the user</TITLE></HEAD>
<% // for uploading the file we used Encrypt type of multipart/
form-data and input of file type to browse and submit the file %>
<BODY> <FORM ENCTYPE="multipart/form-data" ACTION=
"uploadfile.html" METHOD=POST>
<br><br><br>
<center><table border="2" >
<tr><center><td colspan="2"><p align=
"center"><B>PROGRAM FOR UPLOADING THE FILE</B><center></td></tr>
<tr><td><b>Choose the file To Upload:</b>
</td>
<td><INPUT NAME="F1" TYPE="file"></td></tr>
<tr><td colspan="2">
<p align="right"><INPUT TYPE="submit" VALUE="Send File" ></p></td></tr>
<table>
</center>
</FORM>
</BODY>
</HTML>
文件名--uploadfile.html
<%@ page import="java.io.*" %>
<%
//to get the content type information from JSP Request Header
String contentType = request.getContentType();
//here we are checking the content type is not equal to Null and
as well as the passed data from mulitpart/form-data is greater than or
equal to 0
if ((contentType != null) && (contentType.indexOf("multipart/
form-data") >= 0)) {
DataInputStream in = new DataInputStream(request.
getInputStream());
//we are taking the length of Content type data
int formDataLength = request.getContentLength();
byte dataBytes[] = new byte[formDataLength];
int byteRead = 0;
int totalBytesRead = 0;
//this loop converting the uploaded file into byte code
while (totalBytesRead < formDataLength) {
byteRead = in.read(dataBytes, totalBytesRead,
formDataLength);
totalBytesRead += byteRead;
}
String file = new String(dataBytes);
//for saving the file name
String saveFile = file.substring(file.indexOf("filename=\
"") + 10);
saveFile = saveFile.substring(0, saveFile.indexOf("\n"));
saveFile = saveFile.substring(saveFile.lastIndexOf("\\")
+ 1,saveFile.indexOf("\""));
int lastIndex = contentType.lastIndexOf("=");
String boundary = contentType.substring(lastIndex + 1,
contentType.length());
int pos;
//extracting the index of file
pos = file.indexOf("filename=\"");
pos = file.indexOf("\n", pos) + 1;
pos = file.indexOf("\n", pos) + 1;
pos = file.indexOf("\n", pos) + 1;
int boundaryLocation = file.indexOf(boundary, pos) - 4;
int startPos = ((file.substring(0, pos)).getBytes()).length;
int endPos = ((file.substring(0, boundaryLocation))
.getBytes()).length;
// creating a new file with the same name and writing the
content in new file
FileOutputStream fileOut = new FileOutputStream(saveFile);
fileOut.write(dataBytes, startPos, (endPos - startPos));
fileOut.flush();
fileOut.close();
%><Br><table border="2"><tr><td><b>You have successfully
upload the file by the name of:</b>
<% out.println(saveFile); %></td></tr></table> <%
}
%>
i want to upload a pdf file by using code given below.It give browsing facility but dont upload file. When i click sendfile button Its display uploadfile.html code page. How can i do that???
where is the error in the given code???
filename-upload.html
<%@ page language="java" %>
<HTml>
<HEAD><TITLE>Display file upload form to the user</TITLE></HEAD>
<% // for uploading the file we used Encrypt type of multipart/
form-data and input of file type to browse and submit the file %>
<BODY> <FORM ENCTYPE="multipart/form-data" ACTION=
"uploadfile.html" METHOD=POST>
<br><br><br>
<center><table border="2" >
<tr><center><td colspan="2"><p align=
"center"><B>PROGRAM FOR UPLOADING THE FILE</B><center></td></tr>
<tr><td><b>Choose the file To Upload:</b>
</td>
<td><INPUT NAME="F1" TYPE="file"></td></tr>
<tr><td colspan="2">
<p align="right"><INPUT TYPE="submit" VALUE="Send File" ></p></td></tr>
<table>
</center>
</FORM>
</BODY>
</HTML>
filename--uploadfile.html
<%@ page import="java.io.*" %>
<%
//to get the content type information from JSP Request Header
String contentType = request.getContentType();
//here we are checking the content type is not equal to Null and
as well as the passed data from mulitpart/form-data is greater than or
equal to 0
if ((contentType != null) && (contentType.indexOf("multipart/
form-data") >= 0)) {
DataInputStream in = new DataInputStream(request.
getInputStream());
//we are taking the length of Content type data
int formDataLength = request.getContentLength();
byte dataBytes[] = new byte[formDataLength];
int byteRead = 0;
int totalBytesRead = 0;
//this loop converting the uploaded file into byte code
while (totalBytesRead < formDataLength) {
byteRead = in.read(dataBytes, totalBytesRead,
formDataLength);
totalBytesRead += byteRead;
}
String file = new String(dataBytes);
//for saving the file name
String saveFile = file.substring(file.indexOf("filename=\
"") + 10);
saveFile = saveFile.substring(0, saveFile.indexOf("\n"));
saveFile = saveFile.substring(saveFile.lastIndexOf("\\")
+ 1,saveFile.indexOf("\""));
int lastIndex = contentType.lastIndexOf("=");
String boundary = contentType.substring(lastIndex + 1,
contentType.length());
int pos;
//extracting the index of file
pos = file.indexOf("filename=\"");
pos = file.indexOf("\n", pos) + 1;
pos = file.indexOf("\n", pos) + 1;
pos = file.indexOf("\n", pos) + 1;
int boundaryLocation = file.indexOf(boundary, pos) - 4;
int startPos = ((file.substring(0, pos)).getBytes()).length;
int endPos = ((file.substring(0, boundaryLocation))
.getBytes()).length;
// creating a new file with the same name and writing the
content in new file
FileOutputStream fileOut = new FileOutputStream(saveFile);
fileOut.write(dataBytes, startPos, (endPos - startPos));
fileOut.flush();
fileOut.close();
%><Br><table border="2"><tr><td><b>You have successfully
upload the file by the name of:</b>
<% out.println(saveFile); %></td></tr></table> <%
}
%>
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评论（1）
这显然是 Roseindia 代码片段。首先，这是最差学习资源。不要使用它。它只会教导不好的做法。将该网站添加到您的黑名单中。事实上，任何充斥着广告横幅和过时的低质量代码片段的“教程”网站显然都是由业余爱好者维护的，他们主要关注广告收入而不是认真的教学。此类垃圾“教程”网站的其他示例有 javabeat、tutorialspoint、journaldev、javatpoint 等。这些网站的显着共同点是它们起源于印度。
除了您错误地使用了
.html文件扩展名而不是.jsp（即使他们正确地使用.jsp扩展名展示了他们的示例） ，代码片段存在几个主要问题：和标记，这些标记自 1998 年以来已弃用。Content-Length请求标头，该标头本身并不总是存在。如果缺少此标头，代码就会中断。String。这可能会导致结果字节格式错误/损坏。这简直太可怕了。
从 JSP 上传文件的正确方法是将表单提交给
@MultipartConfig注解的 servlet 类，然后使用request.getPart()获取文件。您可以在此答案中找到一个片段： How to upload files to server using JSP/ Servlet？这个答案详细阐述了学习 Java EE 的正确方法：Java EE Web 开发，我从哪里开始以及我需要哪些技能？
This is clearly a Roseindia code snippet. First of all, it is the worst learning resource ever. Don't use it. It only teaches bad practices. Add that site to your blacklist. In fact, any "tutorial" site which is littered with advertisement banners and hopelessly outdated low quality code snippets are clearly maintained by amateurs with primary focus on advertisement income instead of on serious teaching. Other examples of such crap "tutorial" sites are javabeat, tutorialspoint, journaldev, javatpoint, etc. Remarkable common thing which those sites have is that they are originated in India.
Apart from the fact that you incorrectly used
.htmlfile extension instead of.jsp(even though they presented their examples correctly with.jspextensions), there are several major problems with the code snippet:<font>and<center>tags which are deprecated since 1998.Content-Lengthrequest header which is not always present per se. If this header is absent, the code breaks.Stringbased on the byte array using server platform default character encoding instead of the one specified in multi part header. This may malform/corrupt the result bytes.DataInputStreamwrapper is unnecessary, the code is not taking any benefit of it.It's simply terrible.
The right way to upload a file from JSP is to submit the form to a
@MultipartConfigannotated servlet class and then userequest.getPart()to get the file. You can find a snippet in this answer: How to upload files to server using JSP/Servlet?The right way to learn Java EE is elaborated in this answer: Java EE web development, where do I start and what skills do I need?