Consume a Simple Web Service

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1 Introduction

Mendix is the app platform for the enterprise, and in enterprise software, it is not likely that you work in a greenfield project. In almost every situation, you will need to integrate with existing systems. Mendix supports many ways of integrating, and this how-to focuses on how you can consume web services with Mendix.

For this how-to, you will be using an example web service of W3Schools. Please note that this is a very simple web service that converts temperatures from Celsius to Fahrenheit and vice versa. The converted temperature will be returned as a string value that can be stored in a variable directly. If you want to invoke a web service that returns a complex XML message, you can use the XML-to-domain mappings explained in How to Import XML Documents.

After using this how-to, you will know how to do the following:

  • Import a WSDL
  • Create logic to call the web service

2 Importing a WSDL

A WSDL describes the operations of a web service and can be imported in the Modeler. After importing the WSDL, you can invoke the operations of the web service instantly within the microflow editor.

To import a WSDL, follow these steps:

  1. Right-click your module in the Project Explorer and select Add > Document from the menu (you can also use shortcut Ctrl+N):
  2. Select Consumed web service as the Document type in the New Document pop-up window, and then select a module or folder as the target Location:
  3. Click OK and enter a name for the new consumed web service (for example, TemperatureConverter).
  4. Click OK again. You will now see the consumed web service editor:
  5. Enter http://www.w3schools.com/xml/tempconvert.asmx?WSDL as the URL, and then click Import. This will bring up the Select Ports pop-up window asking you to select a web service port:
  6. Click OK to select the default. The Modeler should now import these operations: CelsiusToFahrenheit and FahrenheitToCelsius.
  7. Click OK to save the consumed web service.

3 Creating Logic to Call the Web Service

To create logic to call the web service, follow these steps:

  1. Right-click your module in the Project Explorer and select Add > Document from the menu (you can also use shortcut Ctrl+N):
  2. Select Microflow as the Document type in the New Document pop-up window, and then select a module or folder as target Location:
  3. Click OK and enter a name for the new microflow (for example, ConvertCelsiusToFahrenheit).
  4. Click OK again. You will now see an empty microflow:
  5. Open the Toolbox (from the bottom-right corner of the Modeler): You can also open the Toolbox from the view menu:
  6. Drag a Create variable activity from the Toolbox to the line between the start and end event. This inserts a new activity.
  7. Double-click the new activity to open the Create Variable properties editor.
  8. Select Integer/Long as the Data Type, enter 100 as the value, and set TemperatureInCelsius as the Output Variable name:
  9. Click OK. The microflow will look like this:
  10. Drag a Call web service activity from the toolbox to the line between the start and end event. This inserts a new activity.
  11. Double-click the new activity to open the Call Web Service properties editor:
  12. In the Web service call section of the editor, click Select… to open the Select Web Service Operation pop-up window:
  13. Select CelsiusToFahrenheit and then click Select.
  14. Double-click the Celsius (optional) input parameter:
  15. Enter toString($TemperatureInCelsius) for the expression. The web service operation expects a string value, which is why you need to use the toString function. Then click OK.
  16. Select Yes for the Store in variable option, and name the variable TemperatureInFahrenheit:
  17. Click OK. The microflow will look like this:
  18. Drag a Show message activity from the Toolbox to the line between the start and end event. This inserts a new activity.
  19. Double-click the new activity to open the Show Message properties editor.
  20. Select Information as the Type, and enter The temperature in fahrenheit is: {1} for the Template. The {1} functions as a placeholder for the parameters below.
  21. Create a new parameter and enter $TemperatureInFahrenheit for the expression (this is the return value of the web service operation), and click OK:
  22. Click OK again to save the Show message activity properties. The microflow will look like this:
  23. Create a menu item that triggers this microflow. For details on how to create a menu item, see How to Set Up the Navigation Structure.
  24. Deploy the application and trigger the microflow to call the web service operation. You should see a message with the converted temperature.

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