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Mule Filters, Scopes, and Routers

Mule Runtime Engine versions 3.5, 3.6, and 3.7 reached End of Life on or before January 25, 2020. For more information, contact your Customer Success Manager to determine how you can migrate to the latest Mule version.

Mule includes a variety of message processors designed to facilitate message routing or filtering, and message processor wrapping.

  • Filters evaluate a message to determine whether it can proceed through a flow. The simplest filters implement basic logic operators (such as and, or, and not), but these simple elements can be combined in various ways to specify complex logical conditions. For example, you can use a filter near the beginning of your flow to reject any requests from a particular range of IP addresses, or simply use a filter to reject any messages with a particular payload, or with a null payload.

  • Scopes work to encapsulate other message processors so that they function as a single unit. You might wrap several message processors together to form a transactional unit, so that they succeed or fail to process a message together, thus ensuring accurate updating of a database, for example. You might wrap several message processors together within a cache scope to store the result of their processing for reuse, or wrap a single message processor within a message enricher scope to add to a message payload without manipulating the original contents.

  • Routers – or flow controls, as they’re known in Anypoint Studio – function much as their name implies: to direct or otherwise control messages within a flow.

At times, flow controls act as splitters, resequencers, or aggregators, splitting messages into individual items for processing, resequencing message content, or aggregating split messages.

At times, they act as forks in the road, evaluating a message’s payload, properties, or variables, then routing to the message down a particular "pathway" according to those contents. Thus, flow controls facilitate content-based routing. For example, you can use a choice flow control to examine part of a message payload, then route the message to the first "pathway" for which the set condition evaluates to true, such as where an order exceeds $5,000.

Examples

Expression Filter

<mule xmlns="http://www.mulesoft.org/schema/mule/core" xmlns:http="http://www.mulesoft.org/schema/mule/http" xmlns:doc="http://www.mulesoft.org/schema/mule/documentation" xmlns:spring="http://www.springframework.org/schema/beans" xmlns:core="http://www.mulesoft.org/schema/mule/core"  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.mulesoft.org/schema/mule/http http://www.mulesoft.org/schema/mule/http/current/mule-http.xsd
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-current.xsd
http://www.mulesoft.org/schema/mule/core http://www.mulesoft.org/schema/mule/core/current/mule.xsd">

    <flow name="EchoFlow" doc:name="EchoFlow">
        <http:inbound-endpoint exchange-pattern="request-response" host="localhost" port="8084" doc:name="HTTP" doc:description="Process HTTP requests or responses."/>
        <expression-filter expression="#[message.payload != '/favicon.ico']" doc:name="Expression"/>
        <logger message="About to echo #[message.payload]" level="INFO" doc:name="Logger"/>
        <echo-component doc:name="Echo"/>
    </flow>

</mule>

Message Enricher and Cache Scope

...

<flow doc:name="inhouseOrder" name="inhouseOrder">
        <jms:inbound-endpoint connector-ref="Active_MQ" doc:name="inhouseOrder" queue="inhouseOrder">
            <xa-transaction action="ALWAYS_BEGIN"/>
        </jms:inbound-endpoint>
        <set-variable doc:name="Initialise Price" value="0" variableName="price"/>
        <enricher doc:name="Enrich with price" target="#[price]">
            <ee:cache cachingStrategy-ref="Caching_Strategy" doc:name="Cache the Price">
                <http:outbound-endpoint disableTransportTransformer="true" doc:name="Invoke Price Service" exchange-pattern="request-response" host="localhost" method="GET" path="api/prices/#[payload.productId]" port="9999"/>
                <object-to-string-transformer doc:name="Object to String"/>
            </ee:cache>
        </enricher>
        <db:insert config-ref="Generic_Database_Configuration" doc:name="Save Order Item" transactionalAction="ALWAYS_JOIN">
            <db:parameterized-query><![CDATA[insert into orders (product_id, name, manufacturer, quantity, price) values (#[payload.productId], #[payload.name], #[payload.manufacturer], #[payload.quantity], #[price])]]></db:parameterized-query>
        </db:insert>
        <set-variable doc:name="totalPrice = price * payload.quantity" value="#[price * payload.quantity]" variableName="totalPrice"/>
        <set-session-variable doc:name="totalValue += totalPrice" value="#[totalValue + totalPrice]" variableName="totalValue"/>
        <scripting:transformer doc:name="Groovy">
            <scripting:script engine="Groovy">
                <scripting:text><![CDATA[receipt = new com.mulesoft.se.orders.PurchaseReceipt(); receipt.setStatus(com.mulesoft.se.orders.Status.ACCEPTED); receipt.setTotalPrice(Float.valueOf(message.getInvocationProperty('totalPrice')));
return receipt;]]></scripting:text>
            </scripting:script>
        </scripting:transformer>
        <rollback-exception-strategy doc:name="Rollback Exception Strategy" maxRedeliveryAttempts="3">
            <logger doc:name="Logger" level="INFO" message="#[payload]"/>
            <on-redelivery-attempts-exceeded doc:name="Redelivery exhausted">
                <flow-ref doc:name="Invoke defaultErrorHandler" name="defaultErrorHandler"/>
            </on-redelivery-attempts-exceeded>
        </rollback-exception-strategy>
    </flow>
...

</mule>

Message Enricher and Cache

Choice Router

<mule
...
    xmlns:vm="http://www.mulesoft.org/schema/mule/vm" xmlns:http="http://www.mulesoft.org/schema/mule/http"
...
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.mulesoft.org/schema/mule/cxf http://www.mulesoft.org/schema/mule/cxf/current/mule-cxf.xsd

http://www.mulesoft.org/schema/mule/vm http://www.mulesoft.org/schema/mule/vm/current/mule-vm.xsd

http://www.mulesoft.org/schema/mule/http http://www.mulesoft.org/schema/mule/http/current/mule-http.xsd">

...
    <flow name="orderService" doc:name="orderService">
        <http:inbound-endpoint exchange-pattern="request-response"
            host="localhost" port="1080" path="orders" doc:name="/orders"
            doc:description="Process HTTP reqests or responses." connector-ref="HttpConnector" />
        <cxf:jaxws-service serviceClass="com.mulesoft.se.orders.IProcessOrder"
            doc:name="Order WebService" doc:description="Make a web service available via CXF" />
        <set-session-variable variableName="totalValue"
            value="0" doc:name="totalValue=0" />
        <foreach collection="#[payload.orderItems]" doc:name="For each Order Item">
            <enricher
                target="#[rootMessage.payload.orderItems[counter - 1].purchaseReceipt]"
                doc:name="Enrich with purchase receipt">
                <choice doc:name="Choice">
                    <when expression="#[payload.manufacturer == 'Samsung']">
                        <vm:outbound-endpoint exchange-pattern="request-response"
                            path="samsungOrder" doc:name="Dispatch to samsungOrder" />
                    </when>
                    <otherwise>
                        <jms:outbound-endpoint exchange-pattern="request-response"
                            queue="inhouseOrder" connector-ref="Active_MQ" doc:name="Dispatch to inhouseOrder" />
                    </otherwise>
                </choice>
            </enricher>
        </foreach>
        <vm:outbound-endpoint exchange-pattern="one-way"
            path="audit" responseTimeout="10000" mimeType="text/plain" doc:name="Dispatch to audit" />
        <catch-exception-strategy doc:name="Catch Exception Strategy">
            <flow-ref name="defaultErrorHandler" doc:name="Invoke defaultErrorHandler" />
        </catch-exception-strategy>
    </flow>
    ...

</mule>

See Also