Storing and Forwarding Messages

Store and forward messaging is used for serving traffic to back-end services that can accept request messages only at a given rate. This is also used for guaranteed delivery to ensure that request received never gets lost since they are stored in the message store and also available for future reference. 

Let's get started!

Creating the Message Store

1. Righ click on SampleServices in the Project Explorer and navigate to New->Message Store. 

2. Select Create a new message-store artifact and fill in the information in the following table and click Finish.

   Field	Value
   Message Store Name	PaymentRequestMessageStore
   Message Store Type	Select In Memory Message Store

   

Let's look at how we update the REST API with the Store mediator.

Creating the Deployable Artifacts

Let's now update the REST API so that the messages sent to SettlePaymentEP is forwarded to the message store we created above. 

1. Drag and add a Store Mediator from the mediators palette just after the PayloadFactory mediator.
   

2. With the Store mediator selected, access the Properties tab and fill in the information as in the following table:

   Field	Value	Description
   Available Message Store	Select PaymentRequestMessageStore	After selecting this, when you click Message Store field the value will be populated.
   Description	Payment Store

   Let's use a PayloadFactory mediator to send a customized response message to the client. 

3. Delete the Call mediator by right clicking on the mediator and selecting Delete from Model. Replace this with a PayloadFactory mediator from the Mediators palette to configure the response to be sent to the client. With the PayloadFactory mediator selected, access the Properties tab and fill in the information in the following table to define a customized message to be returned to the client.

   Field	Value
   Payload Format	Select Inline
   Payload	{"message":" Payment request successfully submitted. Payment confirmation will be sent via email ."}
   Media Type	Select json

   To avoid getting an error message, first select Media Type before selecting Payload.

    

   You should now have a completed configuration that looks like this:
   

Creating the Response Sequence

Let's create a Sequence  that uses the message in the message store to send the request to SettlePaymentEP.

1. Right click the SampleServices project in the Project Explorer and navigate to New -> Sequence. Select Create New Sequence and provide the name PaymentRequestProcessingSequence.

   
   Click Finish.

2. Drag and drop a Call mediator from the Mediators palette  and add SettlePaymentEP from Defined Endpoints palette to the empty box adjoining the Call mediator. This sends the request message from the store to SettlePaymentEP.

   

3.  Drag and drop a Log mediator from the Mediators palette to log the response from SettlePaymentEP. Access the Properties tab and fill in the following information:

   Field	Value
   Log Category	Select INFO
   Log Level	Select FULL

4. Add a Drop mediator from the Mediators palette.

   You should now have a completed sequence configuration that looks like this:

   
   

Creating the Message Processor

Let's create a Message Sampling Processor to dispatch the request message from the message store to the PaymentRequestProcessingSequence.

Right click the  SampleServices  project in the Project Explorer and navigate to  New -> Message Processor . Select create a new message-processor artifact and fill in the details as in the following table:

Click Finish.

We have now finished creating all the required artifacts.

Deploying the Artifacts to WSO2 EI

Since you created a message store, sequence and a message processor,  these will need to be packaged into our existingCApp.

1. Package the C-App names SampleServicesCompositeApplication project with the artifacts created. 

    

   Ensure the following artifact check boxes are selected in the Composite Application Project POM Editor.

   • SampleServices
     • HealthcareAPI
     • ClemencyEP
     • GrandOakEP
     • PineValleyEP
     • ChannelingFeeEP
     • SettlePaymentEP
     • PaymentRequestMessageStore
     • PaymentRequestProcessingSequence
     • PaymentRequestProcessor
   • SampleServicesRegistry

2. On the Servers tab, expand the WSO2 Carbon server, right-click SampleServicesCompositeApplication, and choose Redeploy. The Console window will indicate that the CApp has been deployed successfully.

    

   If you do not have a server added in Eclipse, refer this tutorial.

    

   You can also deploy the artifacts to Enterprise Integrator using a Composite Application Archive (CAR) file

Sending requests to WSO2 EI

1. Create a JSON file names request.json with the following request payload.

    

   {
   "name": "John Doe",
   "dob": "1940-03-19",
   "ssn": "234-23-525",
   "address": "California",
   "phone": "8770586755",
   "email": "johndoe@gmail.com",
   "doctor": "thomas collins",
   "hospital": "grand oak community hospital",
   "cardNo": "7844481124110331"
   }

2. Open a command line terminal and execute the following command from the location where request.json file you created is saved:
   

   curl -v -X POST --data @request.json http://localhost:8280/healthcare/categories/surgery/reserve --header "Content-Type:application/json"

   This is from the URI-Template defined when creating the API resource QueryDoctorAPI.

   http://<host>:<port>/categories/{category}/reserve

   You will see the response as follows:

    

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

3. Now check the ESB server Console in Eclipse and you will see that the response from SettlePaymentEP is logged.

You have now explored how WSO2 EI can be used to implement store and forward messaging using Message Stores, Message Processors and the Store mediator.