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Definition

The HTTP plug-in handles HTTP requests and responses (see the graphic in the section Structure of the ICM). The URL and the port can be used to access a ‘local’ handler in the ICM. This increases system performance, as it renders it unnecessary to create a user context in the work process for every request. The profile parameters are used to determine which URL prefixes correspond to the various handlers. The handlers are called, and then they either process the request themselves or forward it to the next handler.

See also: Parameterization of the ICM and the ICM Server Cache

Structure

The following section describes the local handlers (subhandlers). They are called in the series described below, provided that they are installed. Which subhandler generates the response depends on how the profile parameters for the URL prefix of the request have been set. If a subhandler created the HTTP response, the following subhandlers are no longer included in the hierarchy. The exception to this is the logging handler, which executes HTTP logging and then passes it on to the next subhandler.

  1. Logging handler

    2. This handler records HTTP requests. For a description of how to use it, see Logging in the ICM.

  2. Server cache handler

This handler reads and writes to the ICM Server Cache and works as follows:
    1. Reads the request
    2. If the requested object is in the cache, delivers the cache entry to the requesting application.
    3. If the requested object is not in the cache, forwards the request to the next handler.
    4. Stores the entry in the cache before sending the HTTP response to the client
  1. File access handler

    2. This handler returns a file from the file system (suitable for static files such as pictures and HTML pages). Parameter icm/HTTP/file_access_<xx> determines the URL prefixes for which the static file access should be carried out.

  2. Redirect handler

    3. This handler forwards the HTTP request to another HTTP server (HTTP redirect). Parameter icm/HTTP/redirect_<xx> determines the ICM URL prefixes for which the redirect should be executed.

  3. SAP R3 handler

    4. This handler forwards the request to the SAP System and waits for a response. This is the default handler, that is, it processes a request if no other handler is processing that request. A user context is created in the work process only if this handler is being used.

  4. J2EE handler

This handler passes the request to the integrated J2EE server (see also Integrating the SAP J2EE Application Server).

 

 

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