13.3 The Async Example

Let's take a look at the shipped example Async located in your <installdir>\tutorials\webservices\Async directory. This example illustrates two service operation methods that are implemented asynchronously, one a request/response method, the other a one-way method.

For more information on one-way operations and how they work, see Section 9.2.3, "The One Way Pattern."

This section discusses how to implement the client's asynchronous service operation methods and assumes knowledge of how to generate code and build a client. For background information on creating a client with various options, see Chapter 7, "Developing Clients."

Following is the implementation of the request/response invoke() method in AsyncClient.cpp, the provided implementation of the client.

void invoke_longRunningMethod(AsyncProxy& proxy)               //1
{
  std::string input_in("Hello World");
  std::string return_ret;
  try {
    std::cout << "Invoking longRunningMethod" << std::endl;
    rwsf::CallInfo info;
    rwsf::AsyncHandle handle = 
       proxy.longRunningMethodStart(info, input_in);           //2
                 
    if(handle.isFinished()) {                                  //3
      return_ret = proxy.longRunningMethodEnd(handle);         //4     
      // return_ret is ready for use!
      // handle's callInfo has response headers, etc.
      rwsf::CallInfo retInfo = handle.getCallInfo();           //5
    }
    else {
      std::cout << "Still waiting" << std::endl;
      return_ret = proxy.longRunningMethodEnd(handle);         //6
    }
    std::cout << "Return value = " << return_ret << std::endl;
    
  } catch(const rwsf::SoapFaultException& e) {                 //7
    std::cout << "Fault Code: " 
    << e.getFault().getFaultcode().asString() << std::endl;
    std::cout << "Fault String: " << e.getFault().getFaultstring()
    << std::endl;
  }
}

This section discusses implementing a one-way method asynchronously. Even though a one-way method expects no response, you may wish to implement it asynchronously, allowing you to make another call on the proxy without waiting for the transport to return.

This discussion assumes background knowledge on one-way methods and how they work. For information, see Section 9.2.3, "The One Way Pattern."

Now let's look at the implementation of the one-way invoke() method in AsyncClient.cpp in the <installdir>\tutorials\Async directory.

void invoke_oneWayMethod(AsyncProxy& proxy)                     //1
{
  std::string input_in("Hello World");

  rwsf::CallInfo info;
  std::cout << "Invoking oneWayMethod" << std::endl;            //2
  rwsf::AsyncHandle handle =                                    //3
      proxy.oneWayMethodStart(info,input_in);
  proxy.oneWayMethodEnd(handle);                                //4

  std::cout << "Finished executing the one way method" 
  << std::endl;                                                 //5
}

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Make sure that you have set up your environment as described in Chapter 2, "Installation," in the HydraExpress User's Guide. On Windows, be sure you have set up your command window with the MSVC environment.

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To run this example:

1. Generate code by opening a command prompt and navigating to the directory <installdir>\tutorials\webservices\Async. Enter

<prompt> rwsfgen example-project.xml

to direct HydraExpress to generate code into the directory AsyncExample based on the Async.wsdl. You could also enter the options and WSDL file manually, as follows:

<prompt> rwsfgen -projectname AsyncExample Async.wsdl

The HydraExpress project file example-project.xml includes all options and files to be used as an argument to the code generator, so using this file results in exactly the same generated code as providing the options and files directly. For more information on the use of HydraExpress project files in the shipped examples, see Chapter 2, "Installation," in the HydraExpress User's Guide.

2. Before building this example, copy the provided sample files from the <installdir>\tutorials\webservices\Async to the new AsyncExample directory, allowing the provided files to overwrite the generated files, as follows:

AsyncClient.cpp	Copy to AsyncExample\app\client
AsyncImp.cpp	Copy to AsyncExample\app\server

3. Navigate to the directory AsyncExample, and build the example by entering nmake (Win32) or make (UNIX/Linux).

4. To deploy the service, shut down the Agent servlet container if it is running, run nmake (Windows) or make (Linux or UNIX) for the deploy target, and restart the server. The command sequence to deploy the service is shown below:

   Win32	%RWSF_HOME%\bin\rwsfserver stop nmake deploy %RWSF_HOME%\bin\rwsfserver start
   UNIX/Linux	$RWSF_HOME/bin/rwsfserver stop make deploy $RWSF_HOME/bin/rwsfserver start

5. Change to the directory, AsyncExample\bin, and run the client by entering

prompt>AsyncClient

The service returns the following:

Invoking longRunningMethod
Still waiting           //service simulates a 5 second delay
Return value = Hello World
Invoking oneWayMethod
Finished executing the one way method

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