Sample 7: Using Schema Validation and the Usage of Local Registry for Storing Configuration Metadata

Introduction

This sample demonstrates how to use the Validate Mediator for XML schema validation and how to use the local registry (local entries) to store configuration metadata.  Here you will send a message from the sample client to the back-end service through the ESB and shows how a static XML fragment could be made available to the ESB's local registry. It is assumed that the resources defined in the local registry are static (never changes over the lifetime of the configuration) and may be specified as a source URL, inline text or inline XML.

Prerequisites

For a list of prerequisites, see Prerequisites to Start the ESB Samples.

Building the sample

The XML configuration for this sample is as follows: 

<definitions xmlns="http://ws.apache.org/ns/synapse">

    <localEntry key="validate_schema">
        <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns="http://services.samples"
                   elementFormDefault="qualified" attributeFormDefault="unqualified"
                   targetNamespace="http://services.samples">
            <xs:element name="getQuote">
                <xs:complexType>
                    <xs:sequence>
                        <xs:element name="request">
                            <xs:complexType>
                                <xs:sequence>
                                    <xs:element name="stocksymbol" type="xs:string"/>
                                </xs:sequence>
                            </xs:complexType>
                        </xs:element>
                    </xs:sequence>
                </xs:complexType>
            </xs:element>
        </xs:schema>
    </localEntry>

    <sequence name="main">
        <in>
            <validate>
                <schema key="validate_schema"/>
                <on-fail>
                    <!-- if the request does not validate againt schema throw a fault -->
                    <makefault>
                        <code value="tns:Receiver" xmlns:tns="http://www.w3.org/2003/05/soap-envelope"/>
                        <reason value="Invalid custom quote request"/>
                    </makefault>
                </on-fail>
            </validate>
        </in>
        <send/>
    </sequence>
</definitions>

This configuration file  synapse_sample_7.xml is available in the <EI_HOME>/samples/service-bus directory.

To build the sample

1. Start the ESB Profile with the sample 7 configuration. For instructions on starting a sample ESB configuration, see Starting the ESB with a sample configuration.
   
   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 ESB instance and a back-end service deployed. In the next section, we will send a message to the back-end service through the ESB using a sample client.

Executing the sample

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.

According to the configuration file synapse_sample_7.xml, the schema is made available under the validate_schema key. The Validate Mediator by default operates on the first child element of the SOAP body. You can specify an XPath expression using the source attribute to override this behaviour. Here, the Validate Mediator uses the validate_schema resource to validate the incoming message and if the message validation fails, it invokes the on-fail sequence of mediators.

To execute the sample client

• Run the following command from the <EI_HOME>/samples/axis2Client directory.

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

Analyzing the output

When you send the stock quote request,  the schema validation fails and a fault is generated back with the message Invalid custom quote request. This is because the schema used in the example expects a slightly different message than what is created by the stock quote client. The schema used in the example expects a stocksymbol element instead of symbol to specify the stock symbol.