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SAP Sybase SQL Anywhere 16.0 » SQL Anywhere Server - Programming » HTTP web services » SQL Anywhere as an HTTP web server » How to develop web service applications in an HTTP web server


How to access client-supplied SOAP request headers

Headers in SOAP requests can be obtained using a combination of the NEXT_SOAP_HEADER and SOAP_HEADER functions. The NEXT_SOAP_HEADER function iterates through the SOAP headers included within a SOAP request envelope and returns the next SOAP header name. Calling it with NULL causes it to return the name of the first header. Subsequent headers are retrieved by passing the name of the previous header to the NEXT_SOAP_HEADER function. This function returns NULL when called with the name of the last header.

The following example illustrates the SOAP header retrieval:

SET hd_key = NEXT_SOAP_HEADER( hd_key );
    IF hd_key IS NULL THEN
      -- no more header entries
      LEAVE header_loop;
    END IF;

Calling this function repeatedly returns all the header fields exactly once, but not necessarily in the order they appear in the SOAP request.

The SOAP_HEADER function returns the value of the named SOAP header field, or NULL if not called from an SOAP service. It is used when processing an SOAP request via a web service. If a header for the given field-name does not exist, the return value is NULL.

The example searches for a SOAP header named Authentication. When it finds this header, it extracts the value for entire SOAP header and the values of the @namespace and mustUnderstand attributes. The SOAP header value might look something like this XML string:

<Authentication xmlns="CustomerOrderURN" mustUnderstand="1">
  <userName pwd="none">

For this header, the @namespace attribute value would be CustomerOrderURN

Also, the mustUnderstand attribute value would be 1

The interior of this XML string is parsed with the OPENXML function using an XPath string set to /*:Authentication/*:userName.

SELECT * FROM OPENXML( hd_entry, xpath )
    WITH ( pwd LONG VARCHAR '@*:pwd',
        first_name LONG VARCHAR '*:first/text()',
        last_name LONG VARCHAR '*:last/text()' );

Using the sample SOAP header value shown above, the SELECT statement would create a result set as follows:

pwd first_name last_name
none John Smith

A cursor is declared on this result set and the three column values are fetched into three variables. At this point, you have all the information of interest that was passed to the web service.