The next step in the development process is to model the implementation of the operation getProduct. At the end of this development step, your activity diagram will look like the following:

Adding Parameters to the Activity Diagram

The activity diagram Get Product will contain actions to define an exchange rate and to receive and process input data.

Objects represent object flow through activities and can change their state. Objects may originate outside of the context of an activity diagram – in other words, they are input parameters to the activity diagram. On the other side, activity diagrams may produce objects that are used as output. They can be passed as output parameters to an outside context, which can be a calling activity diagram or a port type operation.

Previously, you defined the operation getProduct, its parameters, and the implementing activity diagram. Now, you will add the two parameters to the activity diagram in the diagram pane to model the object flow. Remember that each activity parameter node works as a container of a parameter. They have a different color than normal object nodes that are drawn in the activity diagram and indicate that these nodes contain activity parameters. In order to visualize input and output parameters, you can place them on the left or right side of the diagram frame. The left side corresponds to input, the right side to output.

In order to get a better overview, click the white rectangle to automatically resize the diagram section. Now, the whole diagram fits into the diagram pane.

Copying UML Elements

Before implementing the new functionality, you will copy some UML symbols from the port type operation diagram Get Title to the new port type operation diagram Get Product.

Save  the UML model.

Mapping Input to Output

Remember that by defining dependencies between the attributes of the input and output class, the input data can easily be mapped to the output data.
Now, you will initiate this mapping by using the <<Mapping>> stereotype in an action. This action then will internally translate the declarations defined in class diagrams into a set of action script statements that actually execute the mapping. Later on in this lesson when tracing the compiled service with the E2E Analyzer, you can see this in more detail.

The input and output objects will be added to the diagram as parameters.

Image Modified	Select the action node Map Product Record Data with the right mouse button and choose Stereotype.
Image Modified	Start typing ma to filter the list. Select Mapping and click Apply.
Image Modified	The stereotype <<Mapping>> specifies the action Map Product Record Data as a special action having no action script. The mapping stereotype is indicated by the icon Image Modified in the upper left corner of the action node. The data mapping is done as defined in the class diagram Product Query Classes. The involved classes are identified by the object flows connected to this mapping action.

As the currency conversion is not done yet, the output data of the mapping action will not flow directly to the output parameter outputProductRecord, but will be temporarily stored in a Central Buffer Node. This UML symbol is used to store information only within the activity diagram. The information is not passed outside the context of the activity diagram.

While the central buffer node is used for the object flow within the context of the activity diagram, the activity parameter node is used to pass the data to the outside context. The object flow only leads to the parameter node when the object outputProductRecord does not change its state anymore. Here, this will be right after the currency calculation that is implemented further below.

Save  the UML model.

Using Call Operation Actions

In the next step, you will call a class operation in order to get the exchange rate for CHF / USD. The operation getExchangeRate is a member of class CurrencyCalculator. The operation returns a parameter called exchangeRateCHFUSD being of type Float. In UML, operations are called using Call Operation Actions.

The call operation action node is displayed in a different color than normal actions. It visualizes an action calling an operation. The name of the called operation is displayed in the call operation action node.
As the operation getExchangeRate has the output parameter exchangeRateCHFUSD, an output pin is docked to the action node. Name and type of the object is displayed next to the pin. By default, a target pin is created automatically, too (see orange mark in the picture below).

 
An output pin holds output values produced by an action. The value can be delivered to other actions via object flows. At the same time, objects can be transformed to other objects having a different name using pins. This increases modeling speed and helps avoiding modeling errors. It would be equivalent to use a central buffer node instead of a pin, however, it is best practice to use pins in this case.

As it is an output pin and in order to visualize the information flow, we recommend dragging the output pin to the right border of the call operation action node.

Save  the UML model.

Using Action Script

In the next (and last) action, you will use the float exchangeRateCHFUSD, which was received from operation getExchangeRate, in order to convert the price in USD to the price in CHF. The price in USD was taken from the input object (inputProductRecord) and has already been mapped to the object outputProductRecord. In the next step, you will update this object with the calculated price in CHF and the exchange rate, before the object is returned to the calling client.

Completing the Object and the Control Flow

Before editing the action script of the next action, you will first complete the control and the object flow. Having completed the object flow you get full editing support of the Action Script Editor.

The new action Set Price CHF and Exchange Rate needs some input data: the exchange rate and the output product record data, which has to be updated.

Now, the processed data must be passed to the output parameter.

Processing the Data Using Action Script

In the next modeling step, you will define the action script of the action Set Price CHF and Exchange Rate. Within this action script, you will set the exchange rate to the output parameter and perform the currency calculation.

You can reference the attribute exchangeRate of class outputProduct-Record by writing the object name followed by a dot and the attribute name (outputProductRecord.exchangeRate). Use the set assignment statement in order to assign a value to an attribute being of a base type (here Float).

The notion exchangeRate:Float in the suggestion list indicates that the attribute is of base type Float.

In the second action script statement, you will perform the currency calculation. The price in USD will be converted to the price in CHF. You will use arithmetic operators in the set assignment statement and assign the value of attribute priceUSD multiplied with the value of object exchangeRateCHFUSD to the value of attribute priceCHF.

Enter the following action script using the script editing features.
set outputProductRecord.priceCHF = outputProductRecord.priceUSD * exchangeRateCHFUSD;

The action script is now shown in the tagged value script within the action node Set Price CHF and Exchange Rate. Note that the stereotype <<ActionScript>> was applied to the action node as well.

Save  the UML model.

Next, you will implement the class operation getExchangeRate().

Implementing the Class Operation

Besides attributes, there are operations that are defined on classes. Basically, these operations can be called within a service instance but not externally by other processes, clients, etc. However, if you like to publish class interfaces, for instance as Web service interfaces, you can give the class the stereotype <<E2ESOAPPortType>>. A port type accumulates operations that a client can call on a Web service. If you want to publish other interfaces like SAP RFC modules or HTTP operations, the Bridge provides other appropriate stereotypes.

While defining the Classes you defined the class CurrencyCalculator, which has no attributes and one operation getExchangeRate.
The operation getExchangeRate is defined as static. That means, no instance of the class has to be created to use the operation. In chapter Using Call Operation Action, you directly called this operation in the activity diagram via the Call Operation Action, in order to get the exchange rate for the currency conversion.

Now, you will implement this operation in the activity diagram, you already defined before. It is already assigned to the class operation getExchangeRate. The activity diagram is located in the containment tree directly within the class element. Navigate to the activity diagram Get Exchange Rate (in Data - Services - GetProductService - Classes - Currency Calculator) and open it.
Now add the required diagram components. Add the following to the diagram pane:

• an initial node 
• an action node 
• and an activity final node 

The most effective way to draw this is described below.

Frequently, it is necessary to store literals global to an xUML service. In the Bridge context, it is possible to define name value pairs that are configurable by the E2E Embedded Runtime respectively the E2E Bridge. These name value pairs are called settings.

For the moment, you will hard code the exchange rate as a fix value that can be edited via the xUML service settings. In lesson 3, you will extend the service by implementing a call to an external Web service in order to get the exchange rate.

The implementations of the activity diagrams are finished now.

Save  the UML model.

The next step in the development process is to modify the component diagram.