Gem #102: SOAP/WSDL client part
by Pascal Obry —EDF R&D
Let's get started...
This is the second part of a two-part Gem series on SOAP and WSDL.
In this Gem we will be using a Web Service as described in a WSDL document. These services could be implemented in Java, C#, or Ada, because the WSDL is universal in the Web Services world.
In the previous Gem we generated a WSDL from a simple Ada spec. Let's use it to generate the necessary code to use these Web services. We again use the wsdl2aws tool, but this time to generate only the stubs:
$ wsdl2aws -f -noskel temperatures.wsdl
A set of packages is generated. Two are of interest to us at the moment, namely:
Package temperatures_service-types.ads, containing the types used by the Web services.
Package temperatures_service-client.ads, containing the Web services client spec.
For each Web Service routine, two specs are generated:
function To_Fahrenheit (C : Celsius_Type; Endpoint : String := Temperatures_Service.URL; Timeouts : AWS.Client.Timeouts_Values := Temperatures_Service.Timeouts) return To_Fahrenheit_Result; function To_Fahrenheit (Connection : AWS.Client.HTTP_Connection; C : Celsius_Type) return To_Fahrenheit_Result; -- Raises SOAP.SOAP_Error if the operation fails
The first connects and closes the connection for each call, whereas the second uses a persistent connection. The usage is straightforward. Now, let's build a small program which converts Celsius to Fahrenheit:
with Ada.Text_IO; with Temperatures_Service.Client; with Temperatures_Service.Types; procedure SOAP_Client is use Ada; use Temperatures_Service; C : constant Types.Celsius_Type := 20.0; F : constant Types.Fahrenheit_Type := Client.To_Fahrenheit (C); package C_IO is new Text_IO.Float_IO (Types.Celsius_Type); package F_IO is new Text_IO.Float_IO (Types.Fahrenheit_Type); begin Text_IO.Put ("Celsius "); C_IO.Put (C, Aft => 1, Exp => 0); Text_IO.New_Line; Text_IO.Put ("Fahrenheit "); F_IO.Put (F, Aft => 1, Exp => 0); Text_IO.New_Line; end SOAP_Client;
We can use the following simple project file to build this program:
with "aws"; project SOAP_Client is for Source_Dirs use ("."); for Main use ("soap_client.adb"); end SOAP_Client;
$ gnatmake -gnat05 -Psoap_client
Now let's test it, first by starting the server we have built last week:
Then running soap_client:
$ ./soap_client Celsius 20.0 Fahrenheit 68.0
That's all there is to it. As we've shown, it's easy to use a Web Service in Ada when the WSDL is provided. It's still possible to use a Web Service without a WSDL, but in that case it would be necessary to hand-code it.soap_client.zip