what are the codes for uploading and downloading files in and from database?

We are designing a student's website where they can get and post study materials. We actually need the code to upload and download files in and from the database. we will be very gratefull if you provide us those with a bit of explanations.

Thank you.

View Answers

April 16, 2011 at 12:53 PM

1)page.jsp:

<%@ page language="java" %>
<HTML>
<HEAD><TITLE>Display file upload form to the user</TITLE></HEAD>
<BODY> <FORM ENCTYPE="multipart/form-data" ACTION="upload.jsp" METHOD=POST>
<br><br><br>
<center>
<table border="0" bgcolor=#ccFDDEE>
<tr>
<center>
<td colspan="2" align="center"><B>UPLOAD THE FILE</B><center></td>
</tr>
<tr>
<td colspan="2" align="center">&nbsp;</td>
</tr>
<tr>
<td><b>Choose the file To Upload:</b></td>
<td><INPUT NAME="file" TYPE="file"></td>
</tr>
<tr>
<td colspan="2" align="center">&nbsp;</td>
</tr>
<tr>
<td colspan="2" align="center"><input type="submit" value="Send File"> </td>
</tr>
<table>
</center>
</FORM>
</BODY>
</HTML>

2)upload.jsp:

<%@ page import="java.io.*" %>
<%@ page import="java.sql.*" %>
<%@ page import="java.util.zip.*"%>
<%
String saveFile="";
String contentType = request.getContentType();
if((contentType != null)&&(contentType.indexOf("multipart/form-data") >= 0)){
DataInputStream in = new DataInputStream(request.getInputStream());
int formDataLength = request.getContentLength();
byte dataBytes[] = new byte[formDataLength];
int byteRead = 0;
int totalBytesRead = 0;
while(totalBytesRead < formDataLength){
byteRead = in.read(dataBytes, totalBytesRead,formDataLength);
totalBytesRead += byteRead;
}
String file = new String(dataBytes);
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;
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;
File ff = new File(saveFile);
FileOutputStream fileOut = new FileOutputStream(ff);
fileOut.write(dataBytes, startPos, (endPos - startPos));
fileOut.flush();
fileOut.close();
%><Br><table border="2"><tr><td><b>You have successfully upload the file:</b>
<%out.println(saveFile);%></td></tr></table>
<%
Connection connection = null;
String connectionURL = "jdbc:mysql://localhost:3306/test";
ResultSet rs = null;
PreparedStatement psmnt = null;
FileInputStream fis;
try{
Class.forName("com.mysql.jdbc.Driver").newInstance();
connection = DriverManager.getConnection(connectionURL, "root", "root");
File f = new File(saveFile);
psmnt = connection.prepareStatement("insert into file(file_data) values(?)");
fis = new FileInputStream(f);
psmnt.setBinaryStream(1, (InputStream)fis, (int)(f.length()));
int s = psmnt.executeUpdate();
if(s>0){
System.out.println("Uploaded successfully !");
}
else{
System.out.println("Error!");
}
}
catch(Exception e){e.printStackTrace();}
}
%>
<a href="downloadFile.jsp?f=<%=saveFile%>">Download File</a>

April 16, 2011 at 12:54 PM

3)downloadFile.jsp:

<%@ page import="java.util.*,java.io.*"%>
<%@ page import="java.sql.*" %>

<%@ page import="java.net.*"%>
<%!
public static String getMimeType(String fileUrl)
throws java.io.IOException, MalformedURLException
{
String type = null;
URL u = new URL(fileUrl);
URLConnection uc = null;
uc = u.openConnection();
type = uc.getContentType();
return type;
}

%>
<%
String file=request.getParameter("f");
File f = new File (file);
String filename=f.getName();
String type=getMimeType("file:"+file);

ServletOutputStream output = response.getOutputStream();
String connectionURL = "jdbc:mysql://localhost:3306/test";
String Content=new String("");
try{
Class.forName("com.mysql.jdbc.Driver").newInstance();
Connection con=DriverManager.getConnection(connectionURL,"root","root");
Statement st=con.createStatement();
ResultSet rst= st.executeQuery("select * from file");
if(rst.last())
{
Content=rst.getString("file_data");
}
con.close();
}catch(Exception e){
System.out.println("Exception caught"+e.getMessage());
}
byte requestBytes[] = Content.getBytes();
ByteArrayInputStream bis = new ByteArrayInputStream(requestBytes);
response.reset();

response.setContentType (type);
response.setHeader ("Content-Disposition", "attachment; filename=\""+filename+"\"");byte[] buf = new byte[1024];
int len;
while ((len = bis.read(buf)) > 0){
output.write(buf, 0, len);
}
bis.close();
response.getOutputStream().flush();
%>
%>