Using Data Mapper Mediator in the ESB Profile

Prerequisites

Set up the following prerequisites before you begin.

Download and run WSO2 EI. For instructions, see Running the Product.
Install the WSO2 EI Tooling to use the Data Mapper mediator, which supports the data mapping editor. For instructions, see Installing WSO2 Integration Studio.
Download and launch a REST client into your web browser. For example, this guide uses the Postman REST client to send the requests to the ESB profile and receive the responses.

Introduction

This sample demonstrates how to create a mapping configuration for different data formats using the Data Mapper mediator. It uses a simple the ESB profile configuration with only a Data Mapper mediator, and a Respond mediator to check the converted message. The input employee message in XML format, and the output engineer message in JSON format, which is sent to the client as the response.

Creating the ESB configuration project

Follow the steps below to create an ESB configuration project to contain the Data Mapping configurations using WSO2 Ei Tooling .

Open WSO2 EI Tooling.
Right click on the Project Explorer area, click New, and then click EI Solution Project as shown below.

WSO2 EI Tooling now provides this new option to create an EI Solution Project for you to define all different configurations you need for the project using a wizard.
Enter a name for the project, and untick Create Connector Exporter Project (since you do not need Connectors in your configuration) in the following wizard page.
Click Finish.You view the following project files created in the Project Explorer tab.
Right click ESBDataMappingProject workspace file, click New, and then click REST API as shown below, to create a new REST API project in the ESB profile.

Select Create A New API Artifact, and then click Next as shown below.
Enter a name for the Synapse API Artifact, enter /convertMenu for Context to configure the REST API project to listen for POST requests on the /convertMenu URL, and then click Finish as shown below.
Drag and drop a Data Mapper mediator and a Respond mediator as shown below.
Click on the API Resource, and then click on its Properties tab, and select True as the value for the Post method as shown below, to create the API resource listening to POST requests.
Double click on the Data Mapping mediator, t o configure it. You view a dialog box to create a registry resource project.
Enter a name for the configuration, and point the Registry Resource project to save it as shown below.

This configuration name is the prefix used for the configuration files that you deploy to the EI server related to the Data Mapper. Since you created an ESB Solution project, it directly points you to that project to save in it. Otherwise, you need to click the Create new project link, to create a new Registry Resource project and then point to it.
Click OK. You view the following Data Mapper diagram editor in the new WSO2 Data Mapper Graphical perspective.

You can switch to another perspective by either selecting another in top toolbar tags or by c licking Window->Perspective->Open Perspective->Other in the top menu bar.

Create an XML file (e.g., input.xml) by copying the following sample content of a food menu, and save it in your local file system.

Use this sample XML message to load the input format to the Data Mapper editor.

<breakfast_menu>
    <food>
        <name>Belgian Waffles</name>
        <price>$5.95</price>
        <description>Two of our famous Belgian Waffles with plenty of real maple syrup</description>
        <calories>650</calories>
        <orgin>Belgian</orgin>
        <veg>true</veg>
    </food>
    <food>
        <name>Strawberry Belgian Waffles</name>
        <price>$7.95</price>
        <description>Light Belgian waffles covered with strawberries and whipped cream</description>
        <calories>900</calories>
        <orgin>Belgian</orgin>
        <veg>true</veg>
    </food>
    <food>
        <name>Berry-Berry Belgian Waffles</name>
        <price>$8.95</price>
        <description>Light Belgian waffles covered with an assortment of fresh berries and whipped cream</description>
        <calories>900</calories>
        <orgin>Belgian</orgin>
        <veg>true</veg>
    </food>
    <food>
        <name>French Toast</name>
        <price>$4.50</price>
        <description>Thick slices made from our homemade sourdough bread</description>
        <calories>600</calories>
        <orgin>French</orgin>
        <veg>true</veg>
    </food>
    <food>
        <name>Homestyle Breakfast</name>
        <price>$6.95</price>
        <description>Two eggs, bacon or sausage, toast, and our ever-popular hash browns</description>
        <calories>950</calories>
        <orgin>French</orgin>
        <veg>false</veg>
    </food>
</breakfast_menu>

Right-click on the top title bar of the Input box and, click Load Input as shown below. The operation palettes that appear on the left-hand side allows you to provide the input message format to begin the mapping.
Select XML as the Resource Type as shown below.
You can select one out of the following resource types, to load the input and output message formats to Data Mapper.
- XML: to load a sample XML message and WSO2 Data Mapper Editor will generate the JSON schema to represent the XML according to the WSO2 Data Mapper Schema specification.
- JSON: to load a sample JSON message.
- CSV: to load a sample JSON/CSV message. For CSV you need to provide the column names as the first record.
- XSD: to load an XSD schema file, which defines your XML message format.
- JSONSCHEMA: to load a JSON schema for your message according to the WSO2 Data Mapper schema specification.
- CONNECTOR: to map a message, which is an output of a Connector. Select the Connector Type in the Input box, and it will list down all available connectors. Then, select the operation from the menu that appears in front of Data Mapper mediator.
Click the file system link in Select resource from, select the XML file you saved in your local file system in step 12, and click Open.
You view the input format loaded in the Input box in the editor as shown below.

Create another XML file (e.g., output.xml) by copying the following sample content of a food menu, and save it in your local file system.

Use this sample XML message to load the output format to the Data Mapper editor.

<menu>
    <item>
        <name>Belgian Waffles</name>
        <price>$5.95</price>
        <calories>650</calories>
        <orgin>Belgian</orgin>
        <veg>true</veg>
        <description>Two of our famous Belgian Waffles with plenty of real maple syrup</description>
    </item>
    <item>
        <name>Strawberry Belgian Waffles</name>
        <price>$7.95</price>
        <calories>900</calories>
        <orgin>Belgian</orgin>
        <veg>true</veg>
        <description>Light Belgian waffles covered with strawberries and whipped cream</description>
    </item>
    <item>
        <name>Berry-Berry Belgian Waffles</name>
        <price>$8.95</price>
        <calories>900</calories>
        <orgin>Belgian</orgin>
        <veg>true</veg>
        <description>Light Belgian waffles covered with an assortment of fresh berries and whipped cream</description>
    </item>
    <item>
        <name>French Toast</name>
        <price>$4.50</price>
        <calories>600</calories>
        <orgin>French</orgin>
        <veg>true</veg>
        <description>Thick slices made from our homemade sourdough bread</description>
    </item>
    <item>
        <name>Homestyle Breakfast</name>
        <price>$6.95</price>
        <calories>950</calories>
        <orgin>French</orgin>
        <veg>false</veg>
        <description>Two eggs, bacon or sausage, toast, and our ever-popular hash browns</description>
    </item>
</menu>

Right-click on the top title bar of the Output box and, click Load Output as shown below . The operation palettes that appear on the left-hand side allows you to provide the output message format.
Click the file system link in Select resource from, select the XML file you saved in your local file system in step 16, and click Open.
You view the input format loaded in the Output box in the editor as shown below.
Check the Input and Output boxes with the sample messages, to see if the element types (i.e. (Arrays, Objects and Primitive values) are correctly identified or not. Following signs will help you to identify them correctly.
- {} - represents object elements
- [] - represents array elements
- <> - represents primitive field values
- A - represents XML attribute values
Click on the Data Mapper mediator. You view the following in the Properties tab of the Data Mapper mediator configuration as shown below.
- Configuration: Script file that is used to execute the mapping.
- Input Schema: JSON schema, which represents the input message format.
- Output Schema: JSON schema, which represents the output message format.
- Input Type: Expected input message type (xml/json/csv).
- Output Type: Target output message type (xml/json/csv).
Check if you set the input and type and output type correctly.

If you do not set the input type and output type correctly in the mediator configuration, your mapping will fail during runtime.
Follow the steps below to do the mapping using operators as shown below.
- The mapping done in the below example is that: name is mapped via uppercase operator and calories undergo a mathematical calculation to get the output as follows:
  output calories =Round( (calories*1.13) + 6.75)
- You can only connect primitive data values such as Strings, numbers, boolean and etc. You cannot map Array and object values.
1. Drag and drop an Upper Case operator and connect the name in both Input and Output boxes to it.
2. Connect price in the Input box to the same in the Output box.
3. Connect description in the Input box to the same in the Output box.
4. Connect origin in the Input box to the same in the Output box.
5. Connect veg in the Input box to the same in the Output box.
6. Dran and drop the following operators: Multiply, Add, Round
7. Drag and drop a Constant operator, and enter 1.13 as its Value in the Properties section.
  
  To update the titile of the Constant box with the value, save the diagram, close the FoodMapping.datamapper_diagram and re-open it by double-clicking on the Data Mapper icon in the FoodMenuConversion.xml file.
8. Drag and drop another Constant operator, and enter 6.75 as its Value in the Properties section.
9. Connect the calories variable in both the Input and Output boxes via the Operators as shown below.
  From To
  Input Box → calories Multiply Operator
  Constant 1.13 Multiply Operator
  Multiply Operator Add Operator
  Constant 6.75 Add Operator
  Add Operator Round Operator
  Round Operator Output Box → calories
Press Ctrl+S keys in each tab, to save all the configurations.

Deploying the configurations

After creating the Data Mapper configurations, follow the steps below to deploy the created REST API and the configurations in the ESB profile by including them in a C-App.

Open WSO2 EI Tooling.
Expand the C-APP project that was created when you created the ESB Solution project (i.e. EIDataMappingProjectCompositeApplication), and double-click on the POM file. You view the following screen to select project files into the C-APP.

You need to refresh the screen to view the registry resource files . Once you refresh the screen, you view all the artifacts in the workspace.
Click the refresh button in the top right-hand corner to load newly added registry files, as shown below.
Select the REST API file and the three registry resource files containing the mapping configuration, input schema, and output schema as shown below.
- Configuration: Script file that is used to execute the mapping.
- Input schema: JSON schema which represents the input message format.
- Output schema: JSON schema which represents the output message format.
Start WSO2 ESB server. For instructions, see Running the Product.
Click the Servers Tab in WSO2 EI Tooling, and click the No servers are available. Click this link to create a new server... link as shown below.
Click WSO2, click WSO2 Carbon remote server, and then click Next as shown below.
Enter the URL of the WSO2 EI for Server URL, and click Finish as shown below.
You view the WSO2 EI server added in the Servers tab as shown below.
Right-click on WSO2 Carbon remote server at localhost, and then click Add & Remove.
Select the C-App in the Available: box, click Add to move it to the Configured: box, and then click Finish as shown below.
You view the C-App added to the WSO2 EI server as shown below.
Log in to the WSO2 EI Management Console using the following URL and admin/admin credentials: https://<ESB_HOST>:<ESB_PORT>carbon/
Click Main , and then click APIs in the Service Bus menu. You view the deployed REST API invocation URL as shown below.

Invoking the created REST API

Follow the steps below to test invoking the created REST API.

Open Postman REST client.
Enter the following details to create the client message, enter the content of the XML file you created in step 12 as the payload in the text area provided, and click Send as shown below.
- URL: http://<ESB_HOST>:<ESB_PORT>8280/convertMenu
- Method: POST
- Body: raw xml/application
- Message: Enter the inpu
You view the expected JSON message received as shown below.

Similarly, you can use the above instructions to check the following message conversions:

The input employee message in XML format, and the output engineer message in XML/JSON/CSV formats, which is sent to the client as the response. (i.e. XML->XML/JSON/CSV)
The input employee message in JSON format, and the output engineer message in XML/JSON/CSV formats, which is sent to the client as the response. (i.e. JSON->XML/JSON/CSV)
The input employee message in CSV format, and the output engineer message in XML/JSON/CSV formats, which is sent to the client as the response. (i.e. CSV->XML/JSON/CSV)

In the above sample, the output message format is fully compatible to represent as JSON and CSV. However, this is not guaranteed in every occasion. For example, if you have defined a complex XML output message with namespaces and attributes, JSON message or CSV will not be built as expected.

From	To
Input Box → calories	Multiply Operator
Constant 1.13	Multiply Operator
Multiply Operator	Add Operator
Constant 6.75	Add Operator
Add Operator	Round Operator
Round Operator	Output Box → calories