Sequence Mediator

The Sequence Mediator refers to an already defined sequence element, which is used to invoke a named sequence of mediators. This is useful when you need to use a particular set on mediators in a given order repeatedly.

You can alternatively select a pre-defined sequence from the registry as the in/out sequence for a proxy service or a REST service without adding any mediator configurations inline. The difference between these two options are described in the table below.

Attribute	Picking a pre-defined sequence as in/out sequence	Referring to a pre-defined sequence via the Sequence mediator
Adding other mediators	Other mediator configurations that are not already included in the pre-defined sequence cannot be added to the in/out sequence.	Other mediator configurations that are not already included in the pre-defined sequence can be added to the in/out sequence
Applying changes done to the pre-defined sequence	Any changes done to the sequence saved in the registry after it was selected as the in/out sequence will not be considered when carrying out mediation.	Any changes done to the sequence saved in the registry after it was selected as the in/out sequence will be considered when carrying out mediation.

The Sequence mediator is a content-unaware mediator.

Syntax

A sequence ref token refers to a <sequence> element, which is used to invoke a named sequence of mediators.

<sequence key="name"/>

UI Configuration

The parameters available to configure the Sequence mediator are as follows.

Parameter Name

Description

Key Type

This parameter defines whether the key to access the required sequence is a static key or a dynamic key. Possible values are as follows.

Static Key: If this is selected, the key to access the sequence is a static value. You can click either Configuration Registry or Governance Registry as relevant to select the require key from the resource tree for the Referring Sequence parameter.
Dynamic Key: If this is selected, you can define the key to access the sequence as a dynamic value by entering an XPath expression in the Referring Sequence parameter.

Referring sequence

The key to access the sequence saved in the registry. You can enter a static value selected from the resource tree, or an XPath expression based on the option you selected for the Key Type parameter.

Tip

You can click NameSpaces to add namespaces if you are providing an expression. Then the Namespace Editor panel would appear where you can provide any number of namespace prefixes and URLs used in the XPath expression.

Example

In this example, the following sequence named StoreSend is saved in the Configuration registry. It includes a Store Mediator to store the request in a message store named JMSMS and a Send Mediator to send it to an endpoint afterwards.

<sequence xmlns="http://ws.apache.org/ns/synapse" name="conf:/StoreSend">
   <axis2ns4:store xmlns:axis2ns4="http://ws.apache.org/ns/synapse" messageStore="JMSMS" sequence="conf:/repository/components/org.wso2.carbon.throttle/templates"></axis2ns4:store>
   <send>
      <endpoint>
         <address uri="http://localhost:9000/services/SimpleStockQuoteService"></address>
      </endpoint>
   </send>
</sequence>

The Sequence mediator configuration can be as follows to invoke the StoreSend sequence after using a PayloadFactory mediator to transform the contents of the request.

<inSequence xmlns="http://ws.apache.org/ns/synapse">
	<payloadFactory media-type="xml">
      <format>
           <m:checkpriceresponse xmlns:m="http://services.samples/xsd">
               <m:code>$1</m:code>
               <m:price>$2</m:price>
           </m:checkpriceresponse>
      </format>
      <args>
           <arg expression="//m0:symbol" xmlns:m0="http://services.samples/xsd">
           <arg expression="//m0:last" xmlns:m0="http://services.samples/xsd">
      </arg></arg></args>
	</payloadFactory>
   	<sequence key="conf:/StoreSend"></sequence>
</inSequence>