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Connecting Web APIs/Cloud Services

What you'll build

When you integrate the systems in your organizaion, it is also necessary to integrate with third-party systems and its capabilities to enhance your services. WSO2 Micro Integrator uses Connectors for the purpose of referring the APIs of third-party systems.

In this tutorial, when a client sends an appointment reservation request to the Micro Integrator, the client should receive an email confirming the appointment reservation details. To build this use case, you can add a GMail connector to the mediation flow of the REST resource that you defined in the previous tutorial.

Let's get started!

Step 1: Set up the workspace

Set up WSO2 Integration Studio as follows:

  1. Download the relevant WSO2 Integration Studio based on your operating system. The path to the extracted/installed folder is referred to as MI_TOOLING_HOME throughout this tutorial.
  2. If you did not try the asynchronous messaging tutorial yet:
    1. Download the pre-packaged project.
    2. Open WSO2 Integration Studio and go to File -> Import.
    3. Select Existing WSO2 Projects into workspace under the WSO2 category, click Next, and then upload the pre-packaged project.

Optionally, you can set up the CLI tool for artifact monitoring. This will later help you get details of the artifacts that you deploy in your Micro Integrator.

  1. Go to the WSO2 Micro Integrator website.
  2. Click Download -> Other Resources and click CLI Tooling to download the tool.
  3. Extract the downloaded ZIP file. This will be your MI_CLI_HOME directory.
  4. Export the MI_CLI_HOME/bin directory path as an environment variable. This allows you to run the tool from any location on your computer using the mi command. Read more about the CLI tool.

Step 2: Develop the integration artifacts

Creating a Client ID and Client Secret

Follow the steps below if you want to use your own email address for sending the emails.

  1. As the email sender, navigate to the URL and log in to your google account.
  2. If you do not already have a project, create a new project.
  3. Now, navigate again to the URL and click Google APIs -> Credentials -> Create Credential -> OAuth client ID.


    At this point, if the consent screen name is not provided, you will be prompted to do so.

  4. Select Web Application and create a client.

  5. Provide as the redirect URL under Authorized redirect URIs and click Create. The client ID and client secret will then be displayed.


    See Gmail API documentation for details on creating the Client ID and Client Secret.

  6. Click on the Library on the side menu and select Gmail API.

  7. Click Enable.

Obtaining the Access Token and Refresh Token

Follow these steps to automatically refresh the expired token when connecting to Google API:

  1. Navigate to the URL, click at the top right corner of the screen and select Use your own OAuth credentials.

  2. Provide the client ID and client secret you previously created and click Close.

  3. Now under Step 1, select Gmail API v1 from the list of APIs, select all the scopes listed under it, and click Authorize APIs.

  4. You will then be prompted to allow permission, click Allow.

  5. Now , click Exchange authorization code for tokens to generate and display the access token and refresh token.

Importing the Gmail Connector into WSO2 Integration Studio

  1. Right click on Sample Services in the Project Explorer and select Add or Remove Connector.
  2. Select Add Connector and click Next. You are now connected to the WSO2 Connector store.
  3. Find Gmail from the list of connectors and click the Download button (for the Gmail connector).

  4. Click Finish. The connector is now downloaded to your workspace in WSO2 Integration Studio and the connector operations are available in the Gmail Connector palette.

Let's use these connector operations in the configuration.

Update the message flow

The connector operations are used in the sequence named PaymentRequestProcessingSequence. Select this sequence and do the following updates:

  1. Add a Property Mediator just before the Call mediator to retrieve and store the patient's email address.

  2. With the Property mediator selected, access the Property tab of the mediator and fill in the information in the following table:

    Property Description
    Property Name Enter New Property... .
    New Property Name Enter email_id.
    Property Action Enter set .
    Value Type Enter EXPRESSION .
    Value Expression

    Follow the steps given below to specify the expression:

    1. Click the text box for the Value Expression field. This opens the Expression Selector dialog box.
    2. Select Expression from the list.
    3. Enter json-eval($ to overwrite the default expression.
    4. Click OK.
    Description Get Email ID

  3. Add another Property mediator just after the Log mediator to retrieve and store the response sent from SettlePaymentEP. This will be used within the body of the email.

  4. With the Property mediator selected, access the Property tab and specify the details given below.

    Property Value
    Property Name Select New Property
    New Property Name payment_response
    Property Action Select Set
    Value Type Select Expression
    Value Expression json-eval($.)
    Description Get Payment Response
  5. Drag and drop the init method from the Gmail Connector palette adjoining the Property mediator you added in the previous step.

  6. With the init method selected, access the Property tab and specify the details given below.

    Property Value
    Parameter Editor Type Select inline
    userId The sender's email address (use the email address that you used to configure the client ID and secret.)
    accessToken The access token you obtained.
    clientId The client ID you created.
    clientSecret The client secret you created.
    refreshToken The refresh token you obtained.
  7. Add the sendMail method from the Gmail Connector palette and access the Property tab and specify the following details;

    Property Description
    to Enter {$ctx:email_id} as the value. This retrieves the patient email address that was stored in the relevant Property mediator.
    subject Enter Payment Status as the value. This is the subject line in the email that is sent out.
    messageBody Enter {$ctx:payment_response} as the value. This retrieves the payment response that was stored in the relevant Property mediator.

    The updated PaymentRequestProcessingSequence should now look like this:

  8. Save the updated sequence configuration.

  9. Right click on SampleServicesConnectorExporter and navigate to New →  Other → Add/Remove Connectors and select Add connector and click on Next . Select Workspace to list down the connectors that were added.

  10. Select the Gmail connector from the list and click OK and then Finish.

Step 3: Package the artifacts

Package the artifacts in your composite application project (SampleServicesCompositeApplication project), the registry resource project (SampleRegistryResource project), and the Connector project (SampleServicesConnectorExporter project) to be able to deploy the artifacts in the server.

  1. Open the pom.xml file in the composite application project POM editor.
  2. Ensure that the following projects and artifacts are selected in the POM file.

    • SampleServicesCompositeApplicationProject
      • HealthcareAPI
      • ClemencyEP
      • GrandOakEP
      • PineValleyEP
      • ChannelingFeeEP
      • SettlePaymentEP
      • PaymentRequestMessageStore
      • PaymentRequestProcessingSequence
      • PaymentRequestProcessor
    • SampleServicesRegistryProject
    • SampleServicesConnectorExporter
  3. Save the project.

Step 4: Build and run the artifacts

To test the artifacts, deploy the packaged artifacts in the embedded Micro Integrator:

  1. Right-click the composite application project and click Export Project Artifacts and Run.
  2. In the dialog that opens, select the artifacts that you want to deploy.
  3. Click Finish. The artifacts will be deployed in the embedded Micro Integrator and the server will start. See the startup log in the Console tab.


Stop the Micro Integrator before proceeding to test. This is because you need to start the broker profile before starting the Micro Integrator.

Step 5: Test the use case

Let's test the use case by sending a simple client request that invokes the service.

Start the backend service

  1. Download the JAR file of the back-end service from here.
  2. Open a terminal, navigate to the location where your saved the back-end service.
  3. Execute the following command to start the service:

    java -jar Hospital-Service-2.0.0-EI7.jar

Start the Message Broker runtime

Set up the Message Broker profile of WSO2 EI 6.6.0. This is required because the Message Broker profile is used for guaranteed message delivery in this use case.

  1. Download WSO2 EI 6.6.0, which includes the Message Broker profile. The path to this folder is referred to as EI_6.6.0_HOME throughout this tutorial.

  2. Add the following JAR files from the EI_6.6.0_HOME/wso2/broker/client-lib/ directory to the MI_TOOLING_HOME/Contents/Eclipse/runtime/microesb/lib/ (in MacOS) or MI_TOOLING_HOME/runtime/microesb/lib (in Windows/Linux) directory.

    • andes-client-*.jar
    • geronimo-jms_1.1_spec-*.jar
    • org.wso2.securevault-*.jar
  3. Open the deployment.toml file from the MI_TOOLING_HOME/Contents/Eclipse/runtime/microesb/conf/ (in MacOS) or MI_TOOLING_HOME/runtime/microesb/conf/ (in Windows/Linux) directory and add the configurations given below. This is required for enabling the broker to store messages.

    name = "myQueueListener"
    parameter.initial_naming_factory = "org.wso2.andes.jndi.PropertiesFileInitialContextFactory"
    parameter.broker_name = "wso2mb"
    parameter.provider_url = "conf/"
    parameter.connection_factory_name = "QueueConnectionFactory"
    parameter.connection_factory_type = "queue"
    parameter.cache_level = "consumer"
    name = "myQueueSender"
    parameter.initial_naming_factory = "org.wso2.andes.jndi.PropertiesFileInitialContextFactory"
    parameter.broker_name = "wso2mb"
    parameter.provider_url = "conf/"
    parameter.connection_factory_name = "QueueConnectionFactory"
    parameter.connection_factory_type = "queue"
    parameter.cache_level = "producer"
    'connectionfactory.QueueConnectionFactory' = "amqp://admin:admin@clientID/carbon?brokerlist='tcp://localhost:5675'"

To start the Message Broker:

  1. Open a terminal and navigate to the EI_6.6.0_HOME/wso2/broker/bin directory.
  2. Execute the following command to run the message broker.

    • On MacOS/Linux/CentOS:

    • On Windows:


    See the WSO2 EI 6.6.0 documentation for more information on how to run the Message Broker profile.

Restart the Micro Integrator

Let's restart the Micro Integrator with the deployed artifacts:

Right-click the composite application project and click Export Project Artifacts and Run as shown below.

Get details of deployed artifacts (Optional)

Let's use the CLI Tool to find the URL of the REST API (that is deployed in the Micro integrator) to which you will send a request.


Be sure to set up the CLI tool for your work environment as explained in the first step of this tutorial.

  1. Open a terminal and execute the following command to start the tool:


  2. Log in to the CLI tool. Let's use the server administrator user name and password:

    mi remote login admin admin

    You will receive the following message: Login successful for remote: default!

  3. Execute the following command to find the APIs deployed in the server:

    mi api show

    You will receive the following information:

    NAME : HealthcareAPI
    URL : http://localhost:8290/healthcare

Similarly, you can get details of Connectors as well as other artifacts deployed in the server. Read more about using the CLI tool.

Send the client request

Let's send a request to the API resource. You can use the embedded HTTP Client of WSO2 Integration Studio as follows:

  1. Open the HTTP Client of WSO2 Integration Studio.


    If you don't see the HTTP Client tab, go to Window -> Show View - Other and select HTTP Client to enable the client.

  2. Enter the request information as given below and click the Send icon ().

    Method POST
    Headers Content-Type=application/json
    URL http://localhost:8290/healthcare/categories/surgery/reserve

    • The URI-Template format that is used in this URL was defined when creating the API resource: http://:/categories/{category}/reserve.
    { "name": "John Doe", "dob": "1940-03-19", "ssn": "234-23-525", "address": "California", "phone": "8770586755", "email": "", "doctor": "thomas collins", "hospital": "grand oak community hospital", "cardNo": "7844481124110331", "appointment_date": "2025-04-02" }

    • This JSON payload contains details of the appointment reservation, which includes patient details, doctor, hospital, and data of appointment.

If you want to send the client request from your terminal:

  1. Install and set up cURL as your REST client.

  2. Create a JSON file names request.json with the following request payload. Make sure you provide a valid email address so that you can test the email being sent to the patient.

    "name": "John Doe",
    "dob": "1940-03-19",
    "ssn": "234-23-525",
    "address": "California",
    "phone": "8770586755",
    "email": "",
    "doctor": "thomas collins",
    "hospital": "grand oak community hospital",
    "cardNo": "7844481124110331",
    "appointment_date": "2025-04-02"
  3. Open a command line terminal and execute the following command from the location where the request.json file you created is saved:

    curl -v -X POST --data @request.json http://localhost:8290/healthcare/categories/surgery/reserve --header 

Analyze the response

You will see the response as follows:

{"message":"Payment request successfully submitted. Payment confirmation will be sent via email."}

An email will be sent to the provided patient email address with the following details:


If you haven't received the mail yet, there are possibilities that your access token might have expired.

Follow the steps in obtaining-the-access-token-and-refresh-token to obtain a new access token and update the gmail init operation.

Subject: Payment Status
    {"appointmentNo":2,"doctorName":"thomas collins","patient":"John

You have now explored how to import the Gmail connector to the Micro Integrator and then use the connector operations to send emails.