The generated callback handlers

Understand the function of callback handlers, and how to generate them in your client stub.

More and more Web services provide support for the different WS-* specifications. To enable a better interoperability with such services, the fglwsdl tool allows the programmer to modify the SOAP request before it is sent, and to perform additional verifications of the SOAP response before it is returned from the BDL function.

A fglwsdl command with the -domHandler module-name option creates a client stub file based entirely on the DOM API. This eases the manipulation of the XML requests and responses. In the module-name you must provide the name of the module where you implement the three callback handlers for the service operations.

For example, this command performs several operations at once:
fglwsdl -domHandler myCallbacks -soap12 -o myDomStub http://localhost:8090/MyService?WSDL

  • It generates the client stub with DomHandler callbacks based on the WSDL for the service running on the localhost.

  • In the generated stub file (.4gl) it includes an import statement (IMPORT FGL myCallbacks in the sample) to reference the callback functions at runtime.

  • In the generated stub file it adds calls for each operation of a service to execute callbacks you implement in the callback module (myCallbacks in the example).