2. Reading Request Headers from Servlets
Reading headers is very straightforward; just call the
getHeader method of the HttpServletRequest,
which returns a String if the header was supplied on this
request, null otherwise. However, there are a
couple of headers that are so commonly used that they
have special access methods. The getCookies method
returns the contents of the Cookie header, parsed and
stored in an array of Cookie objects. See the separate section
of this tutorial on cookies. The getAuthType and getRemoteUser
methods break the Authorization header into its component
pieces. The getDateHeader and getIntHeader methods read
the specified header and then convert them to Date
and int values, respectively.
Rather than looking up one particular header, you
can use the getHeaderNames to get an Enumeration of
all header names received on this particular request.
Finally, in addition to looking up the request headers, you can get
information on the main request line itself. The
getMethod method returns the main request method (normally
GET or POST, but things like
HEAD, PUT, and DELETE are
possible). The getRequestURI method returns the URI (the
part of the URL that came after the host and port, but before
the form data). The getRequestProtocol returns the third
part of the request line, which is generally "HTTP/1.0"
or "HTTP/1.1".
NEXT
This tutorial is now available as a book: Core Servlets and JavaServer Pages by Marty Hall, published by Sun Microsystems Press.
Read all about it at CoreServlets.com
Server-Side Web Applications using Java Servlets versions 2.1/2.2 and JavaServer Pages (JSP) version 1.0: A Tutorial
© 1999-2000 Marty Hall.
All source code freely available for unrestricted use.
Created for work in the Research and Technology Development Center of the Johns Hopkins University Applied Physics Lab, for courses in the Johns Hopkins Part-Time MS Program in Computer Science, and for various industry seminars and on-site Java short courses.
Please note that this is a first draft of the tutorial, so please send corrections, comments, and suggestions to me at hall@apl.jhu.edu.
Reprinted with permission from the author. Click here to visit the original version
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