Pipes and Filters

This page explains how you can implement a sample scenario of Pipes and Filters EIP using WSO2 Micro Integrator.

Introduction to Pipes and Filters EIP

The Pipes and Filters EIP breaks down a large task into smaller subsets of independent steps chained together. This is useful when a sequence of processing steps is required to perform a single event in an integration scenario. The main use case of this EIP is to maintain independence and flexibility between each processing step.

Info

For more information, see the Pipes and Filters documentation.

Sample scenario

The example scenario depicts how a stock quote request is sent from a client to a service (Stock Quote Service). The request is first received by the WSO2 MI, which transmits the request through the following filters:

• Check Username filter: to verify the username.
• Check User ID filter: to verify the user ID.

Note

Filter Mediators are used in the service to verify the validity of the message (checking the username and user ID).

If the message meets the criteria of the first filter, it passes to the second filter. Once it passes the second filter, the service sends the stock quote request to the back-end service (Stock Quote Service) for processing.

Synapse configurations of the artifacts

Note

When you unzip the ZIP file you downloaded below in step 7 when simulating the sample scenario, you can find the below configurations in the <UNZIPPED_FILE>/src/main/wso2mi/artifacts directory. For more information about these artifacts, go to Develop Integration Solutions.

Proxy ServiceSequenceEnd Point

<?xml version="1.0" encoding="UTF-8"?>
<proxy name="pipes-and-filters-proxy" startOnLoad="true" transports="http https"
    xmlns="http://ws.apache.org/ns/synapse">
    <target>
        <inSequence>
            <!-- Will direct an incoming request to the specified sequence -->
            <sequence key="PipesAndFilters"/>
            <respond/>
        </inSequence>
    </target>
</proxy>

<?xml version="1.0" encoding="UTF-8"?>
<sequence name="PipesAndFilters" trace="disable"
    xmlns="http://ws.apache.org/ns/synapse">
    <log level="full"/>
    <!-- Checks For the User Name -->
    <filter regex="UserName" source="//m0:credentials/m0:name"
        xmlns:m0="http://services.samples">
        <then>
            <filter regex="001" source="//m1:credentials/m1:id"
                xmlns:m1="http://services.samples">
                <then>
                    <call>
                        <endpoint key="StockService"/>
                    </call>
                </then>
                <else>
                    <drop/>
                </else>
            </filter>
        </then>
        <else>
            <drop/>
        </else>
    </filter>
</sequence>

<?xml version="1.0" encoding="UTF-8"?>
<endpoint name="StockService" xmlns="http://ws.apache.org/ns/synapse">
    <address uri="http://localhost:9000/services/SimpleStockQuoteService">
    </address>
</endpoint>

Set up the sample scenario

Follow the below instructions to simulate this sample scenario.

1. Install WSO2 Micro Integrator.

   Info

   Follow the Install the Micro Integrator Runtime documentation for more information.

2. Launch Visual Studio Code with the Micro Integrator for VS Code extension (MI for VS Code) installed.

   Info

   Follow the Install Micro Integrator for VS Code documentation for a complete installation guide.

3. Download the backend service.

4. Extract the downloaded zip file.

5. Open a terminal, and navigate to the axis2Server/bin/ directory inside the extracted folder.

6. Execute the following command to start the axis2server with the SimpleStockQuote backend service:

   On MacOS/Linux/CentOSOn Windows

   sh axis2server.sh
   

   axis2server.bat
   

7. Download the artifacts of the sample.

   

8. Import the artifacts to WSO2 MI.

   Click File -> Open Folder -> Select the extracted ZIP file to import the downloaded ZIP file.

9. Start the project in the WSO2 MI server.

   For instructions, go to Build and Run Documentation.

10. Start SoapUI.

    For instructions on downloading and starting, go to SoapUI Getting Started Documentation.

Execute the sample

Send the following request to the service using SoapUI (or any other SOAP client).

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:ser="http://services.samples"
xmlns:xsd="http://services.samples/xsd">
   <soapenv:Header>
    <ser:credentials>
          <ser:name>UserName</ser:name>
          <ser:id>001</ser:id>
      </ser:credentials>
   </soapenv:Header> 
   <soapenv:Body>
      <ser:getQuote>
         <ser:request>
            <xsd:symbol>msft</xsd:symbol>
         </ser:request>
      </ser:getQuote>
   </soapenv:Body>
</soapenv:Envelope>

Analyze the output

After sending the request to the service through the client, notice that the request is successfully generated in the Stock Quote server. The following output will be printed on the Axis2 server's Console, confirming that the request is successfully received by the back-end service.

Tue Aug 06 10:35:01 IST 2024 samples.services.SimpleStockQuoteService :: Generating quote for : msft

You can view the response in the SOAPUI as follows.

Note

If you send another request by changing the name or ID, the request fails as shown below.