Migration of code Mule 3 to Mule 4 and 'rest-router' is not supported in Mule 4

Question

I have one application which is Mule 3, now I need to migrate it into Mule 4.

I implemented and changed some code but it through exceptions that tag not supported i.e 'rest-router' is not supported.

<rest-router:router templateUri="${igate.url}">
<!--Migration ERROR: The migration of 'rest-router' is not supported.-->
<!-- For more information refer to:-->
<!-- * https://docs.mulesoft.com/mule-runtime/4.1/migration-connectors>--
<!-- * https://beta.docs.stgx.mulesoft.com/beta-mule-migration-tool/mule-runtime/4.1/migration-tool.html#unsupported_connectors-->
<rest-router:post>
<ee:transform xmlns:ee="http://www.mulesoft.org/schema/mule/ee/core" doc:name="JSON to Object">
<ee:message>
<ee:set-payload>%dw 2.0 output application/java --- payload as Object { class: 'com.ifi.igate.model.Transaction'}</ee:set-payload>
</ee:message>
</ee:transform>
<flow-ref name="igate-object-flow" doc:name="igate-object-flow" />
<ee:transform xmlns:ee="http://www.mulesoft.org/schema/mule/ee/core" doc:name="Object to JSON" mimeType="application/json">
<ee:message>
<ee:set-payload>%dw 2.0 output application/json --- payload</ee:set-payload>
</ee:message>
</ee:transform>
</rest-router:post>
</rest-router:router>

Full XML file in Mule 3 which we need to migrate on Mule 4 -

<spring:beans>
            <spring:bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
                <spring:property name="ignoreUnresolvablePlaceholders" value="true"/>
                <spring:property name="location" value="igate.properties"/>
            </spring:bean>
            <spring:bean id="validation" class="com.ifi.igate.integration.iclient.ValidationTransformer">
                <spring:property name="transactionTypes">
                    <spring:list>
                        <spring:value>INQ-REQ</spring:value> 
                        <spring:value>DEP-REQ</spring:value> 
                        <spring:value>WIT-REQ</spring:value> 
                    </spring:list>
                </spring:property>
            </spring:bean>
            <spring:bean id="iGateStub" class="com.ifi.igate.stub.IGateStub">
                <spring:property name="handlers">
                    <spring:map>
                        <spring:entry key="INQ-REQ">
                            <spring:bean class="com.ifi.igate.stub.handlers.InqHandler"/>
                        </spring:entry>
                        <spring:entry key="WIT-REQ">
                            <spring:bean class="com.ifi.igate.stub.handlers.WitHandler"/>
                        </spring:entry>
                        <spring:entry key="DEP-REQ">
                        <spring:bean class="com.ifi.igate.stub.handlers.DepHandler"/>
                    </spring:entry>
                    </spring:map>
                </spring:property>
            </spring:bean>
        </spring:beans>
        <rest-router:config/>
        <http:connector name="httpConnector" doc:name="HTTP\HTTPS">
            <receiver-threading-profile maxThreadsActive="10" />
        </http:connector>
        <flow name="igate-json-flow" doc:name="igate-json-flow">
            <http:inbound-endpoint exchange-pattern="request-response" host="${igate.host}" port="${igate.port}" doc:name="HTTP"/>
            <rest-router:router templateUri="${igate.url}">  
                <rest-router:post> 
                    <json:json-to-object-transformer xmlns:json="http://www.mulesoft.org/schema/mule/json" returnClass="com.ifi.igate.model.Transaction" doc:name="JSON to Object"></json:json-to-object-transformer>  
                    <flow-ref name="igate-object-flow" doc:name="igate-object-flow"/>
                    <json:object-to-json-transformer xmlns:json="http://www.mulesoft.org/schema/mule/json" doc:name="Object to JSON" mimeType="application/json"></json:object-to-json-transformer> 
                </rest-router:post> 
            </rest-router:router>
            <rest-router:router templateUri="${igate-stub.url}">
                <rest-router:post> 
                    <json:json-to-object-transformer xmlns:json="http://www.mulesoft.org/schema/mule/json" returnClass="com.ifi.igate.model.Transaction" doc:name="JSON to Object"/>
                    <component doc:name="IGateStub">
                        <spring-object bean="iGateStub"/>
                    </component>
                    <json:object-to-json-transformer xmlns:json="http://www.mulesoft.org/schema/mule/json" doc:name="Object to JSON" mimeType="application/json"/>
                </rest-router:post>
            </rest-router:router>   
        </flow>
        <sub-flow name="igate-object-flow" doc:name="igate-object-flow">         
            <transformer ref="validation"/>
            <choice>
                <when expression="#[message.payload.trxstatus == 0]">
                    <logger message="#[message.payload.trxreason]" level="ERROR" doc:name="Logger"/>
                </when>
                <otherwise>
                    <set-variable variableName="request" value="#[message.payload]" doc:name="save request"/>
                    <flow-ref name="promotions-flow" doc:name="Promotions Flow"/>
                    <flow-ref name="ifi-membership-flow" doc:name="Accumulate Spending"/>
                    <!-- logger message="Before backend" level="ERROR" doc:name="Logger"/-->
                    <flow-ref name="rewards-flow" doc:name="Rewards Flow"/>
                    <choice>
                        <when expression="#[message.payload.values['PTS']>0 || message.payload.trxtype=='INQ-REQ']">
                            <flow-ref name="${igate.membership}-membership-flow" doc:name="External Membership Flow"/>
                        </when>
                        <otherwise>
                            <vm:outbound-endpoint exchange-pattern="request-response" path="membership/ifi" />
                    </otherwise>
                    </choice>
                    <!-- logger message="After backend" level="ERROR" doc:name="Logger"/-->
                    <flow-ref name="promotions-flow" doc:name="Promotions Flow"/>
                    <flow-ref name="rewards-flow" doc:name="Rewards Flow"/>
                    <flow-ref name="ifi-membership-flow" doc:name="Manage balances"/>
                    <flow-ref name="pricing-flow" doc:name="Pricing Flow"/>
            </otherwise>
             </choice>
        </sub-flow>
    </mule>

'rest-router' is not supported in Mule 4 only need replacement for that tag or How I can migrate it into Mule 4.

Answer 1

rest-router seems to be an unsupported and unmaintained (last commit is from 2012) module for Mule 3. You best bet is to migrate from scratch and use APIKit instead. You will need to write a RAML specification for your API and Studio will create all the needed scaffolding from it.