Get http headers through GenericServlet

Question

hi ,
Is it possible to get the http headers through the GenericServlet. I know i can get it through the HttpServlet. Considering that GenericServlet is parent class of HttpServlet I would think that is possible when I get the InputStream - request.getInputStream I should be able to print the headers too. But that does not seem to be happening ? Any information will be appreciated . thanks -sudhir

Answer 1

Greetings,
hi ,
Is it possible to get the http headers through the GenericServlet. I know i can get it through theTechnically, no. Message headers are intended to provide information to the container/encapsulating server relevant to its part in handling the request. Indeed, most headers are not even relevant to the servlet which provides only an "extension" of the server proper. The headers are available in an HttpServlet[Request] primarily because HttpServlets are intended to operate in place of their CGI counterparts (the CGI spec. converts nearly all headers into environment variables...) though not all headers are converted into accessor-enabled object members.
A GenericServlet, however, is, well, exactly that, "generic". It forms the basis of other protocol-specific implementations (which currently, to my knowledge, includes only HTTP...), and so making those "protocol specific" headers available to an implementation class is the responsibility of the "protocol specific" servlet container.
However, since you're (presumably) running your "generic servlet" in an HTTP-specific container environment, you can always try casting the ServletRequest object to an HttpServletRequest reference and call getHeader on it. ;)
HttpServlet. Considering that GenericServlet is parent class of HttpServlet I would think that is
possibleRefer again to the above.
when I get the InputStream - request.getInputStream I should be able to print the headers too. But
that does not seem to be happening ? Any information will be appreciated.Er, no. Input/output streams relate to the body (i.e. the content...) of the message. Headers relate to the meta-data of the message (i.e. its "envelope") - which, again, contains information relevant to the container. That information could be, for example, "routing instructions" - e.g. "Host" or "Referer" headers - or it could be, for example, "handling instructions" - e.g. "Accept-Encoding" or "Cookie" headers.
In the former case, the headers are mostly of relevance only to the container, though a servlet may also base some part of its processing on them and so they are made accessible through the getHeader method.
In the latter case, they are not necessarily relevant to either (the container or the servlet) though, when relevant, they are most likely relevant to the servlet - whether implicitly ("Accept-Encoding") or explicitly ("Cookie") - and so are made available either in the same "implicit" fashion (getHeader), or through a more "explicit" API call (getCookies).
thanks -sudhirRegards,
Tony "Vee Schade" Cook