$Web Api

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Determine whether web API is available

This method was first avaliable in Model 204 7.8.

$Web_APi indicates whether the current processing is the result of a request to Janus Web Server. The difference between $Web_Api and $Web is that the latter returns 0 on the transactional daemon child (or any transactional descendant) of a web thread whereas the former returns 1, indicating that the $web API is available to the threads.

$Web_Api takes no arguments and returns either a 0 or a 1.


%rc = $Web_Api

Return codes

Code Meaning
0 Web API not available.
1 Web API available.

Usage notes

  • The $Web function is most useful for:
    • Preventing code that should only be run for a web request from running for 3270 (or other non-web) requests.
    • Ensuring that non-web, possibly 3270 specific code, is not run for web requests.
    • While $web functions are available on transactional daemon descendants of web threads, "terminal" output is not captured to the web output buffer as it is for the web thread itself. If a transactional daemon wishes to add data to the web output buffer it should use $Web_Put_Text or $Web_Put_Bin.

    In the example below, the variable %district is set from a form field when running a web request and from a screen field otherwise:

    if $web_api then %district = $web_form_parm('DISTRICT') else %district = %query:district end if

  • $web_api has several advantages over other techniques for determining whether a request is running a web request, such as checking $Web_Port or doing a $VIEW('IODEV'):
    • It is syntactically simple and easy to understand.
    • It works correctly even when a request is being debugged using JANUSDEBUG.
    • It works correctly and does not cause a "CONNECTION WAS LOST" user restart after the connection was closed either with a $Web_Done or by the browser. This can be especially useful if there is web-specific processing, like APSY navigation code, that happens after a $Web_Done.