This documentation is for WSO2 Enterprise Integrator version 6.0.0 . View documentation for the latest release.
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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. 

In this tutorial, instead of sending the request directly to the back-end service, you store the request message into an In Memory Message Store. You then use a Message Processor to retrieve the message from the store and then deliver the message to the back-end service.

See the following topics for a description of the concepts that you need to know when creating WSO2 EI artifacts:

Before you begin,

  1. Install Oracle Java SE Development Kit (JDK) version 1.8.* and set the JAVA_HOME environment variable.
  2. Download the WSO2 EI ZIP file from here, and then extract the ZIP file. 
    The path to this folder will be referred to as <EI_HOME> through out this tutorial.
  3. Select and download the relevant EI tooling ZIP file based on your operating system  from here and then extract the ZIP file.
    The path to this folder will be referred to as <EI_TOOLING> through out this tutorial.
  4. Open the ESB Tooling environment and click File -> Import. Then, select Existing WSO2 Projects into workspace under the WSO2 category, click Next and upload the extracted pre-packaged C-App project. This C-App contains the configurations of the previous tutorial so that you do not have to repeat those steps.

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.

    FieldValue
    Message Store NamePaymentRequestMessageStore
    Message Store TypeSelect 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:

    FieldValueDescription
    Available Message StoreSelect PaymentRequestMessageStoreAfter selecting this, when you click Message Store field the value will be populated.
    DescriptionPayment 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.

    FieldValue
    Payload FormatSelect Inline
    Payload{"message":" Payment request successfully submitted. Payment confirmation will be sent via email ."}
    Media TypeSelect 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:

    FieldValue
    Log CategorySelect INFO
    Log LevelSelect 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.

You can also use the Scheduled Message Forwarding Processor here and define the endpoint within the processor.

 The Message Sampling Processor is used because you need to perform mediation on the request message in the next tutorial.

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:

FieldValueDescription
Message Processor TypeSelect Message Sampling Processor

This processor takes the message from the store and puts it into a sequence.

Message Processor Name PaymentRequestProcessor The name of the scheduled message forwarding processor.
Message StoreSelect PaymentRequestMessageStoreThe message store from which the scheduled message forwarding processor consumes messages.
Processor StateActivateWhether the processor needs to be activated or deactivated.
SequenceSelect PaymentRequestProcessingSequenceThe name of the sequence the message from the store needs to be sent to.

 

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.

 
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