Sending a Simple Message to a Service Using the Micro Integrator

The Micro Integrator profile (MI profile) of WSO2 Enterprise Integrator (WSO2 EI) is designed in a highly container-friendly manner, and thereby, it is ideal for you to use it for Microservices Architecture (MSA)-based solutions, which are deployed in container-based environments. 

Let’s try a simple scenario with respect to a health care service using the Micro Integrator profile, where a patient makes an inquiry specifying the doctor's specialization (category) to retrieve a list of doctors that match the specialization. The required information is available in a backend microservice deployed in the MSF4J profile of WSO2 Enterprise Integrator (WSO2 EI). 

We configure an API resource in the Micro Integrator profile of WSO2 EI that receives the client request, instead of the client sending messages directly to the back-end service, thereby decoupling the client and the back-end service. 

Let's get started!

This tutorial includes the following sections:

Downloading the message mediation artifacts

Requests going through the Micro Integrator profile of WSO2 EI are called messages. You can configure the message mediation process in the Micro Integrator profile that routes all received messages to the back-end service (healthcare service). We use the Eclipse-based WSO2 EI Tooling to create the message mediation artifacts and then deploy them to the Micro Integrator profile of WSO2 EI.

Download the pre-packaged Composite Application, which includes all the message mediation artifacts that are required to send a request through the Micro integrator profile to the back-end service. These artifacts are created using the Eclipse-based WSO2 EI Tooling. For information on creating these artifacts, see Creating the deployable artifacts project.

Deploying the artifacts

Add the CAR file you downloaded to the <EI_HOME>/wso2/microIntegrator/repository/deployment/server/carbonapps directory to deploy it in the Micro Integrator profile.

Starting the Micro Integrator profile

Follow the steps given below to start the Micro Integrator profile.

The C-App will be successfully deployed when the server starts.

Starting the MSF4J profile

To be able to send requests to the back-end service (which is an MSF4J service deployed in MSF4J profile), you need to first start the MSF4J profile:

The Healthcare service is now active and you can start sending requests to the service.

Sending requests to the Micro Integrator profile

Let's send a request to our REST API (HealthcareAPI), which is now deployed in the Micro Integrator profile of WSO2 EI. You will need a REST client like curl for this.

1. Open a command line terminal and enter the following request:

   curl -v http://localhost:8290/healthcare/querydoctor/surgery 

   The above request is formed as per the URI-Template defined when creating the endpoint.

   http://<host>:<port>/healthcare/{uri.var.category}

   The {uri.var.category} of the above URI is derived from the URI-Template defined when creating the API resource.

   http://<host>:<port>/querydoctor/{category}

   Other categories you can try sending in the request are:

   • cardiology

   • gynaecology

   • ent

   • paediatric

2. You will see the response message from the HealthcareService with a list of available doctors and the relevant details.

   [{"name":"thomas collins",
     "hospital":"grand oak community hospital",
     "category":"surgery",
     "availability":"9.00 a.m - 11.00 a.m",
     "fee":7000.0},
    {"name":"anne clement",
     "hospital":"clemency medical center",
     "category":"surgery",
     "availability":"8.00 a.m - 10.00 a.m",
     "fee":12000.0},
    {"name":"seth mears",
     "hospital":"pine valley community hospital",
     "category":"surgery",
     "availability":"3.00 p.m - 5.00 p.m",
     "fee":8000.0}

3. Now, check the Micro Integrator profile's server console in Eclipse, and you will see the following message: 
INFO - LogMediator message = "Welcome to HealthcareService"

   This is the message printed by the Log mediator when the message from the client is received in the In sequence of the API resource.

You have now created and deployed an API resource in the Micro Integrator profile, which receives requests, logs a message using the Log mediator, sends the request to a back-end service using the Send mediator, and returns a response to the requesting client.