For dynamic responses created by application programs, CICS® automatically
provides the HTTP headers that are required for basic messages, depending
on the HTTP protocol version used for the message. You might need to add further
HTTP headers to your response.
Some HTTP headers are created automatically by CICS if the message
requires them. Your application does not need to write these headers. The
full list of headers created by CICS is:
- Connection
- Content-Length
Content-Type (written by CICS,
but can be supplied by a client application if a complex header is required)
- Date
- Expect
- Host
- Server
- TE (written by CICS, but the application can add further instances)
- Transfer-Encoding
- User-Agent
- WWW-Authenticate
Note that some of these headers are appropriate, and created, only when CICS is
an HTTP client. The circumstances in which these headers are created are described
in
HTTP header reference for CICS Web support. If you do write
these headers on a response, CICS does not overwrite them, but uses the versions
provided by your application.
The headers that CICS provides when a response is sent are
the ones that should normally be written for a basic message to be compliant
with the appropriate HTTP protocol specification. You might want to add further
HTTP headers to the response for purposes such as:
- Control of caching and document expiry (for example, Cache-Control, Expires,
Last-Modified)
- Content negotiation (for example, Accept-Ranges, Vary)
- Information for the Web client (for example, Title, Warning, further Content
headers)
If your application program is performing complex actions, or if you
select certain status codes for your response, the HTTP specification to which
you are working is likely to require the use of particular HTTP headers for
your message. When you add any HTTP headers to a response, check the HTTP
specification to which you are working for any important requirements that
apply to those headers. See
The HTTP protocol for
more information about the HTTP specifications.
Write additional
HTTP headers for a message before you issue the WEB SEND command to
send the message. The exception to this rule is if you are writing headers
to be sent as trailing headers on a chunked message, in which case the special
process mentioned below applies. When writing HTTP headers for a response: