Debugging the American Flights App

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Debug your American Flights interface and implementation.

Before You Begin

Complete these procedures:

Add Components

To facilitate debugging, add Set Variable and Logger components to your American Flights implementation:

Open the implementation file (implementation.xml).
After the Database Select operation (<db:select/>) named Query Flights, add a Set Variable component.

In the configuration XML, provide this <set-variable/> configuration:

<set-variable value="#[payload]"
     doc:name="Set variable Payload"
     variableName="databasePayload" />

After the Set Variable component, add a Logger component with this configuration:

<logger doc:name="Log Payload" message="#[
    %dw 2.0
    output application/json
    ---
    payload]" />

Click for the complete implementation XML example.

<flow name="getFlights">
    <logger doc:name="Logger" doc:id="ahcnzm" />
    <db:select doc:name="Query Flights" doc:id="pvuqsc" config-ref="Database_Config" >
        <db:sql>
            <![CDATA[Select * FROM american]]>
        </db:sql>
    </db:select>

    <set-variable value="#[payload]" doc:name="Set variable Payload"
         variableName="databasePayload" doc:id="vtptsr" />  (1)

    <ee:transform doc:name="Transform Message" doc:id="uniqueId" >
        <ee:message >
            <ee:set-payload >
                <![CDATA[
                %dw 2.0
                output application/json
                ---
                payload map ( payload01 , indexOfPayload01 ) -> {
                  ID: payload01.ID,
                  code: (payload01.code1 default "") ++ (payload01.code2 default ""),
                  price: payload01.price default 0,
                  departureDate: payload01.takeOffDate as String default "",
                  origin: payload01.fromAirport default "",
                  destination: payload01.toAirport default "",
                  emptySeats: payload01.seatsAvailable default 0,
                  plane: {
                    "type": payload01.planeType default "",
                    totalSeats: payload01.totalSeats default 0
                  }
                }
                ]]>
            </ee:set-payload>
        </ee:message>
    </ee:transform>

<logger doc:name="Log Payload" message="#[
    %dw 2.0
    output application/json
    ---
    payload]" /> (1)

</flow>

1	Set Variable component
2	Logger component

Proceed to Add Breakpoints.

Learn to set up breakpoints to pause execution of your app.

Add Breakpoints

Add breakpoints to your American Flights project:

Open the interface (interface.xml) for your American Flights project.
Select the Run and Debug icon in the activity bar:
In implementation (interface.xml), add a breakpoint to the line that contains the <flow-ref/> component:

Alternatively, use F9 to add a breakpoint to the line.
Open the implementation file (implementation.xml) for your American Flights project, and add breakpoints to the <db:select/> and <set-variable/> components.
Notice that all the breakpoints are now listed in the Breakpoints panel:
Proceed to Start a Debugging Session.

Run a debugging session, and inspect the message and variables at different points during your app’s execution.

Start a Debugging Session

From the Run and Debug menu, click Debug Mule Application:

The IDE packages the app and opens a new terminal that deploys the app to the embedded Mule runtime engine:
Proceed to Test Your American Flights App.

Test Your American Flights App

After starting your debugging session:

From your IDE, open the Terminal window in the console:
- In the desktop IDE, select View > Terminal.
- In the cloud IDE, click the (menu) icon, and select Terminal > New Terminal.
- For either IDE: Press Ctrl and then press the backtick key (`).
In the terminal, use a curl command to make a GET request to the listener in the interface (interface.xml) instead of the implementation:
```
> curl http://localhost:8081/api/flights
```
Notice the /api/flight in the URI for the listener in the interface. For more information about this step, see Trigger a flow.
In your American Flights project, notice that the execution of the app stops at your first breakpoint:

The breakpoint is located in you interface file (interface.xml).
In your debug toolbar, click the Step Over button to continue execution to the next breakpoint, at the <db:select/> element in implementation.xml.
In the Run and Debug sidebar, notice that the Variables panel provides information about the Mule event at the breakpoint:
Click the Step Over button on your debug toolbar to continue execution to your next breakpoint, at the <set-variable/> element.
In the Variables panel, navigate to Mule Message > Payload, and notice that the database response is an array of flight data:
Proceed to Add a Watch Expression.

Add a Watch Expression

From the Run and Debug sidebar, open the Watch panel.
Click the + icon in the panel, and add the expression payload.^mediaType:
Click the Step Over button until your execution moves to the Transform Message component (<ee:transform/>).
Notice that the payload is application/java:
Continue clicking the Step Over button until you reach the Logger component (<logger>).
Notice that your payload transforms to application/json:

Click the Continue button in the debug toolbar, and notice that the app returns the response from the database to your REST client or browser.