service_chaining_mediation_sequence.xml

<sequence xmlns="http://ws.apache.org/ns/synapse" name="custom_validation">
    <log description="validation_flow_initiated_log" level="custom">
        <property name="validation_flow_initiated_log" value="Custom valiation initiated" />
    </log>
    <payloadFactory description="sample_submission_payload" media-type="json">
        <format>{"scope":"$1","service":"$2"}</format>
        <args>
            <arg evaluator="xml" expression="$ctx:Scopes" />
            <arg evaluator="xml" expression="get-property('transport','service')" />
        </args>
    </payloadFactory>
    <call blocking="true">
        <endpoint>
            <http method="post" uri-template="http://localhost:8595/api/validate">
                <timeout>
                    <duration>60000</duration>
                    <responseAction>fault</responseAction>
                </timeout>
            </http>
        </endpoint>
    </call>
    <filter regex="false" source="json-eval($.validated)">
        <then>
            <log description="validation_failed_log" level="custom">
                <property name="validation_failed_log" value="Validation failed" />
            </log>
            <respond />
        </then>
        <else />
    </filter>
</sequence>