Mule Integration Workshop Message Processor or Routers

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Filter TypesMessage Processor or Routers

Message Processor or Routers Types

Message Processor or RoutersControls how events are sent and received by components in the

system.

Message Processors are used within flows to control how messages are

sent and received within that flow.Message Processor DescriptionAll Broadcast a message to multiple targetsAsync Run a chain of message processors in a separate threadChoice Send a message to the first matching message processorCollection Aggregator Aggregate messages into a message collectionCollection Splitter Split a message that is a collectionCustom Aggregator A custom-written class that aggregates messagesCustom Processor A custom-written message processor

First Successful Iterate through message processors until one succeeds (added in 3.0.1)

Idempotent Message Filter Filter out duplicate message by message ID

Message Processors or Routers (Contd)Message Processor DescriptionIdempotent Secure Hash Message Filter Filter out duplicate message by message content

Message Chunk Aggregator Aggregate messages into a single message

Message Chunk Splitter Split a message into fixed-size chunks

Message Filter Filter messages using a filterProcessor Chain Create a message chain from multiple targetsRecipient List Send a message to multiple endpoints

Request Reply Receive a message for asynchronous processing and accept the asynchronous response on a different channel

Resequencer Reorder a list of messagesRound Robin Round-robin among a list of message processors (added in 3.0.1)Until Successful Repeatedly attempt to process a message until successfulSplitter Split a message using an expression

WireTap Send a message to an extra message processor as well as to the next message processor in the chain

AllAll The All message processor can be used to send the same message to

multiple targets. If any of the targets specified is an endpoint that has a filter configured on

it, only messages accepted by that filter are sent to that endpoint. All messages (if any) returned by the targets are aggregated together and

form the response from this processor. Eg: <all> <jms:endpoint queue="test.queue" transformer-refs="StringToJmsMessage"/>

<http:endpoint host="10.192.111.11" transformer-refs="StringToHttpClientRequest"/> <tcp:endpoint host="10.192.111.12" transformer-refs="StringToByteArray"/> </all>

AsyncAsync The Async message processor runs a chain of message processors in

another thread, optionally specifying a threading profile for the thread to be used.

Eg: <async> <append-string-transformer message="-async" /> <vm:outbound-endpoint path="async-async-out" exchange-pattern="one-way" /> <threading-profile doThreading="true" maxThreadsActive="16"/> </async>

This transforms the current message and sends it to the specified endpoint, using a threadpool that contains up to 16 concurrent threads.

ChoiceChoice The Choice message processor sends a message to the first message

processor that matches. If none match and a message processor has been configured as "otherwise", the message is sent there. If none match and no otherwise message processor has been configured, an exception is thrown.

Eg: <choice> <when expression="payload=='foo'" evaluator="groovy"> <append-string-transformer message=" Hello foo" /> </when> <when expression="payload=='bar'" evaluator="groovy"> <append-string-transformer message=" Hello bar" /> </when> <otherwise>

<append-string-transformer message=" Hello ?" /> </otherwise> </choice> If the message payload is "foo" or "bar", the corresponding transformer is run. If not, the transformer specified under "otherwise" is run.

Collection Aggregator The Collection Aggregator groups incoming messages that have matching

group IDs before forwarding them.

The group ID can come from the correlation ID or another property that links messages together.

Eg:

<collection-aggregator timeout="6000" failOnTimeout="false"/>

Collection Splitter The Collection Splitter acts on messages whose payload is a Collection

type. It sends each member of the collection to the next message processor as

separate messages. Attribute “enableCorrelation” to determine whether a correlation ID is set

on each individual message. Eg:

<collection-splitter enableCorrelation="IF_NOT_SET"/>

Custom Aggregator A Custom Aggregator is an instance of a user-written class that aggregates

messages. This class must implement the interface MessageProcessor. Often, it will be useful for it to subclass AbstractAggregator, which

provides the skeleton of a thread-safe aggregator implementation, requiring only specific correlation logic.

Eg: <custom-aggregator failOnTimeout="true" class="com.mycompany.utils.PurchaseOrderAggregator"/>

First Successful The First Successful message processor iterates through its list of child message

processors, routing a received message to each of them in order until one processes the message successfully. If none succeed, an exception is thrown.

Success is defined as: If the child message processor thows an exception, this is a failure. Otherwise:

If the child message processor returns a message that contains an exception payload, this is a failure.

If the child message processor returns a message that does not contain an exception payload, this is a success.

If the child message processor does not return a message (e.g. is a one-way endpoint), this is a success.

Eg: <first-successful> <http:outbound-endpoint address="http://localhost:6090/weather-forecast" /> <http :outbound-endpoint address="http://localhost:6091/weather-forecast" /> <http:outbound-endpoint address="http://localhost:6092/weather-forecast" /> <vm:outbound-endpoint path="dead-letter-queue" /> </first-successful>

Idempotent Message Filter An idempotent filter checks the unique message ID of the incoming message

to ensure that only unique messages are received by the flow. The ID can be generated from the message using an expression defined in the

idExpression attribute. By default, the expression used is #[message:id], which means the underlying endpoint must support unique message IDs for this to work. Otherwise, a UniqueIdNotSupportedException is thrown.

Eg: <idempotent-message-filter idExpression="#[message:id]-#[header:foo]"> <simple-text-file-store directory="./idempotent"/> </idempotent-message-filter> The optional idExpression attribute determines what should be used as the unique message ID. If this attribute is not used, #[message:id] is used by default.

Idempotent Secure Hash Message Filter This filter calculates the hash of the message itself using a message digest

algorithm to ensure that only unique messages are received by the flow. This approach provides a value with an infinitesimally small chance of a

collision and can be used to filter message duplicates. The hash is calculated over the entire byte array representing the message, so

any leading or trailing spaces or extraneous bytes (like padding) can produce different hash values for the same semantic message content.

This router is useful when the message does not support unique identifiers.

Eg:<idempotent-secure-hash-filter messageDigestAlgorithm="SHA26"> <simple-text-file-store directory="./idempotent"/></idempotent-secure-hash-message-filter>

Idempotent Secure Hash Message Filter also uses object stores, which are configured the same way as the Idempotent Message Filter. The optional messageDigestAlgorithm attribute determines the hashing algorithm that will be used. If this attribute is not specified, the default algorithm SHA-256 is used.

Message Chunk Aggregator After a splitter such as the Message Chunk Splitter splits a message into parts,

the message chunk aggregator router reassembles those parts back into a single message.

The aggregator uses the message's correlation ID to identify which parts belong to the same message.

Eg:<message-chunk-aggregator> <expression-message-info-mapping messageIdExpression="#[header:id]" correlationIdExpression="#[header:correlation]"/></message-chunk-aggregator>

The optional expression-message-info-mapping element allows you to identify the correlation ID in the message using an expression. If this element is not specified, MuleMessage.getCorrelationId() is used. The Message Chunk Aggregator also accepts the timeout and failOnTimeout attributes

Message Chunk Splitter The Message Chunk Splitter allows to split a single message into a number of

fixed-length messages that will all be sent to the same message processor. It will split the message up into a number of smaller chunks according to the

messageSize attribute that you configure for the router. The message is split by first converting it to a byte array and then splitting this

array into chunks. If the message cannot be converted into a byte array, a RoutingException is

raised.

Eg:<message-chunk-splitter messageSize="512"/>

Message Filter The Message Filter is used to control whether a message is processed by using

a filter. In addition to the filter, we can configure whether to throw an exception if the filter does not accept the message and an optional message processor to send unaccepted messages to.

Eg:<message-filter throwOnUnaccepted="false" onUnaccepted="rejectedMessageLogger"> <message-property-filter pattern="Content-Type=text/xml" caseSensitive="false"/></message-filter>

Processor Chain A Processor Chain is a linear chain of message processors which process a

message in order. A Processor Chain can be configured wherever a message processor appears in a Mule Schema

Eg:<wire-tap> <processor-chain> <append-string-transformer message="tap" /> <vm:outbound-endpoint path="wiretap-tap" exchange-pattern="one-way" /> </processor-chain></wire-tap>

Recipient List The Recipient List message processor allows to send a message to multiple

endpoints by specifying an expression that, when evaluated, provides the list of endpoints.

These messages can optionally be given a correlation ID, as in the Collection Splitter

Eg:<recipient-list enableCorrelation="ALWAYS" evaluator="header" expression="myRecipients"/> which finds the list of endpoints in the message header named myRecipients.

Request Reply The Request Reply message processor receives a message on one channel,

allows the back-end process to be forked to invoke other flows asynchronously, and accepts the asynchronous result on another channel.

Eg:<flow name="main">

<vm:inbound-endpoint path="input"/> <request-reply storePrefix="mainFlow">

<vm:outbound-endpoint path="request"/> <vm:inbound-endpoint path="reply"/>

</request-reply> <component class="com.mycompany.OrderProcessor"/>

</flow> <flow name="handle-request-reply">

<vm:inbound-endpoint path="request"/> <component class="come.mycompany.AsyncOrderGenerator"/>

</flow>

The request is received in the main flow and passed to the request-reply router, which implicitly sets the MULE_REPLYTO message property to the URL of its inbound endpoint (vm://reply) and asynchronously dispatches the message to the (one-way) vm://request endpoint, where it is processed by the handle-request-reply flow.

Request Reply - Contd

The main flow then waits for a reply. The handle-request-reply flow passes the message to the AsynchOrderGenerator component. When this processing is complete, the message is sent to vm://reply (the value of the MULE_REPLYTO property.) The asynchronous reply is received and given to the OrderProcessor component to complete the order processing.

In more advanced cases, you might not want the automatic forwarding of the second flow's response to the request-reply inbound endpoint. For instance, the second flow might trigger the running of a third flow, which then generates and sends the reply. In these cases, you can remove the MULE_REPLYTO property with a Message Properties Transformer:

<request-reply storePrefix="mainFlow"> <vm:outbound-endpoint path="request">

<message-properties-transformer scope="outbound"> <delete-message-property key="MULE_REPLYTO"/>

</message-properties-transformer? </vm:outbound-endpoint> <vm:inbound-endpoint path="reply"/>

</request-reply>

Resequencer The Resequencer sorts a set of received messages by their correlation

sequence property and issues them in the correct order. It uses the timeout and failOnTimeout attributes to determine when all the messages in the set have been received.

Eg:<resequencer timeout="6000" failOnTimeout="false"/>

Round Robin The Round Robin message processor iterates through a list of child message

processors in round-robin fashion: the first message received is routed to the first child, the second message to the second child, and so on. After a message has been routed to each child, the next is routed to the first child again, restarting the iteration.

Eg:<round-robin> <http:outbound-endpoint address="http://localhost:6090/weather-forecast" /> <http:outbound-endpoint address="http://localhost:6091/weather-forecast" /> <http:outbound-endpoint address="http://localhost:6092/weather-forecast" /></round-robin>

Splitter A Splitter uses an expression to split a message into pieces, all of which are

then sent to the next message processor. Like other splitters, it can optionally specify non-default locations within the message for the message ID and correlation ID.

Eg:<splitter evaluator="xpath" expression="//acme:Trade"/> This uses the specified XPath expression to find a list of nodes in the current message and sends each of them as a separate message.

Until Successful The Until Successful message processor processes a message with its child

message processor until the processing succeeds. This processing occurs asynchronously, therefore execution is returned to the parent flow immediately.

The Until Successful message processor is able to retry: Dispatching to outbound endpoints, for example, when reaching out to a

remote web service that may have availability issues. Execution of a component method, for example, to retry an action on a

Spring Bean that may depend on unreliable resources. A sub-flow execution, to keep re-executing several actions until they all

succeed. Any other message processor execution, to allow more complex scenarios.

Eg:<until-successful objectStore-ref="objectStore" maxRetries="5" secondsBetweenRetries="60"> <outbound-endpoint ref="retriableEndpoint" /></until-successful> .

Until Successful (Contd) This message processor needs an ListableObjectStore instance in order to persist

messages pending (re)processing. There are several implementations available in Mule, including the following: DefaultInMemoryObjectStore. The default in-memory store. DefaultPersistentObjectStore. The default persistent store FileObjectStore. A file-based store. QueuePersistenceObjectStore. The global queue store. SimpleMemoryObjectStore. An in-memory store

Eg:<spring:bean id="objectStore" class="org.mule.util.store.SimpleMemoryObjectStore" />

Success or failure are defined as: If the child message processor throws an exception, this is a failure. If the child message processor does not return a message (e.g. is a one-way

endpoint), this is a success. If a 'failure expression' has been configured, the return message is evaluated

against this expression to determine failure or not.

Until Successful (Contd) Otherwise:

If the child message processor returns a message that contains an exception payload, this is a failure.

If the child message processor returns a message that does not contain an exception payload, this is a success.

Eg: how to configure the failure expression

<until-successful objectStore-ref="objectStore" failureExpression="#[header:INBOUND: http.status != 202]" maxRetries="6" secondsBetweenRetries="600"> <http:outbound-endpoint address="http://acme.com/api/flakey" exchange-pattern="request-response" method="POST"/></until-successful>

Until Successful (Contd) The Until Successful message processor is also able to synchronously

acknowledge that it has accepted a message and will try to process it repeatedly.

Eg:<until-successful objectStore-ref="objectStore" ackExpression="#[message:correlationId]" maxRetries="3" secondsBetweenRetries="10"> <flow-ref name="signup-flow" /></until-successful>

WireTap The WireTap message processor allows to route certain messages to a

different message processor as well as to the next one in the chain. For instance, To copy all messages to a specific endpoint, configure it as an outbound endpoint on the WireTap routing processor:

Eg:<wire-tap> <vm:outbound-endpoint path="tapped.channel"/></wire-tap>

Using Filters with the WireTap

The WireTap routing processor is useful both with and without filtering. If filtered, it can be used to record or take note of particular messages or to copy only messages that require additional processing.

WireTap (Contd) If filters aren't used, can make a backup copy of all messages received. The

behavior here is similar to that of an interceptor, but interceptors can alter the message flow by preventing the message from reaching the component. WireTap routers cannot alter message flow but just copy on demand. In this example, only messages that match the filter expression are copied to the vm endpoint.

Eg:

<wire-tap> <vm:outbound-endpoint path="tapped.channel"/> <wildcard-filter pattern="the quick brown*"/></wire-tap>

Thank you