Sample 3: Local Registry Entry Definitions, Reusable Endpoints and Sequences

Introduction

This sample demonstrates the functionality of local registry entry definitions, reusable endpoints and sequences.

Prerequisites

For a list of prerequisites, see Prerequisites to start samples.

Building the sample

The XML configuration for this sample is as follows: 

<definitions xmlns="http://ws.apache.org/ns/synapse">
    <!-- define a string resource entry to the local registry -->
    <localEntry key="version">0.1</localEntry>
    <!-- define a reuseable endpoint definition -->
    <endpoint name="simple">
        <address uri="http://localhost:9000/services/SimpleStockQuoteService"/>
    </endpoint>
    <!-- define a reusable sequence -->
    <sequence name="stockquote">
        <!-- log the message using the custom log level. illustrates custom properties for log -->
        <log level="custom">
            <property name="Text" value="Sending quote request"/>
            <property name="version" expression="get-property('version')"/>
            <property name="direction" expression="get-property('direction')"/>
        </log>
        <!-- send message to real endpoint referenced by key "simple" endpoint definition -->
        <send>
            <endpoint key="simple"/>
        </send>
    </sequence>
    <sequence name="main">
        <in>
            <property name="direction" value="incoming"/>
            <sequence key="stockquote"/>
        </in>
        <out>
            <send/>
        </out>
    </sequence>
</definitions>

This configuration file  synapse_sample_3.xml is available in the <EI_HOME>/samples/service-bus directory.

To build the sample

1. Start WSO2 EI with the sample 3 configuration. For instructions on starting a sample configuration, see Starting a sample.
   
   The operation log keeps running until the server starts, which usually takes several seconds. Wait until the server has fully booted up and displays a message similar to "WSO2 Carbon started in n seconds."

2. Start the Axis2 server.For instructions on starting the Axis2 server, see Starting the Axis2 server.

3. Deploy the back-end service SimpleStockQuoteService. For instructions on deploying sample back-end services, see Deploying sample back-end services.

   Now you have a running WSO2 EI instance and a back-end service deployed. In the next section, we will send a message to the back-end service through WSO2 EI using a sample client.

Executing the sample

This example uses a sequence named main that specifies the main mediation rules to be executed. This is equivalent to directly specifying the mediators of the main sequence within the <definitions> tag. This sample scenario is a recommended approach for non-trivial configurations.

The sample client used here is the Stock Quote Client, which can operate in several modes. For further details on this sample client and its operation modes, see Stock Quote Client.

To execute the sample client

• Run the following command from the <EI_HOME>/samples/axis2Client directory, to trigger a sample message to the back-end service.

  ant stockquote -Daddurl=http://localhost:9000/services/SimpleStockQuoteService -Dtrpurl=http://localhost:8280/

Analyzing the output

Analyze the mediation log on the WSO2 EI start-up console.

You will see that a sequence named main is executed. Then, for the incoming message flow, the In Mediator executes and it calls the sequence named stockquote.

DEBUG SequenceMediator - Sequence mediator <main> :: mediate()
DEBUG InMediator - In mediator mediate()
DEBUG SequenceMediator - Sequence mediator <stockquote> :: mediate()

You will also see that the stockquote sequence is executed. and that the log mediator dumps a simple text/string property which is the result of an XPath evaluation, that picks up the key named version, and a second result of an XPath evaluation that picks up a local message property set previously by the property mediator. The get-property() XPath extension function is able to read message properties local to the current message, local or remote registry entries, Axis2 message context properties as well as transport headers. The local entry definition for version defines a simple text/string registry entry, which is visible to all messages that pass through WSO2 EI.

[HttpServerWorker-1] INFO LogMediator - Text = Sending quote request, version = 0.1, direction = incoming
[HttpServerWorker-1] DEBUG SendMediator - Send mediator :: mediate()
[HttpServerWorker-1] DEBUG AddressEndpoint - Sending To: http://localhost:9000/services/SimpleStockQuoteService