have you set the content type in your
application's web.xml file????

No, just in the servlet/jsp...................

I read too fast and whether it's necesary to put the
contenttype in the web.xml. I think it's not necessary, you just have to set
this value in the servlet.

As specified below I am trying to open  the pdf  Document by using servile, in my
code i am setting the Mime type - application/pdf.

Here i am sending my code, Please take a look and suggest  me for the best
possibility.

public void service(javax.servlet.ServletRequest req,
javax.servlet.ServletResponse res)
throws javax.servlet.ServletException, java.io.IOException
{
HttpServletResponse hResponse = (HttpServletResponse) res; // Creating the
responce object.
String sMimetype = "application/pdf";
hResponse.setContentType(sMimetype);
hResponse.setStatus(hResponse.SC_OK);
OutputStream out = hResponse.getOutputStream();
byte[] bOutput = (byte[])agaDataDoc.getProperty("doccon"); // Reading the
document content from the database  and costing into byte array.
out.write(bOutput);
}

you should try this code in doGet or doPost methods.