Mediation Sequences

Use the Mediation Sequences page to add new sequences or edit existing sequences. As shown in Figure,1 the sequence management section displays a list of existing sequences. Defined sequences tab shows sequences saved in synapse configuration. Dynamic sequences tab shows sequences saved in registry.

Figure 1: Mediation sequence management

In the navigator, under Manage/Service Bus, click Sequences. The Mediation Sequences page appears.

Enable Statistics
- Click Enable Statistics to gather information relating to a particular sequence.
Enable Tracing
- Click Enable Tracing to turn on all trace messages for the corresponding sequence

The above options are turned off by default because they cause a severe performance degradation. Use these options only in a situation where you have to debug a particular problem. Dynamic sequences does not support Enable Statistics and Enable Tracing.

Edit
- Click Edit to open the sequence in the design view for editing purposes.
Delete
- Click Delete to remove a particular sequence from the system.

Adding a Sequence

On the Mediation Sequences page, click Add Sequence. The Design Sequence page appears.
Enter a sequence name.
Click Add Child, and select the required nodes for your sequence. Each option is described under Field descriptions

Figure 2: Add sequence design view

Adding a dynamic sequence

On the design sequence page click on the Save As button. You'll be displayed Save As Synapse Registry Entry section.
Select Governance Registry or Configuration Registry
Provide the key of the dynamic resource. This key will act as the path where the resource will be added in Registry.

Figure 2.1: Add a dynamic sequence

The saved dynamic sequence will be displayed as follows

Figure 2.2: Saved dynamic sequence

Editing a sequence

On the Mediation Sequences page, click Edit. The Design Sequence page appears, displaying the selected sequence.

Figure 3: Editing a sequence
Click on the node you want edit. The properties for that node will be displayed below.

Figure 4: Editing node specific properties

You can edit the node specific attributes displayed in the Design view.
You can add a sibling node, in the Design view..
You can add only siblings to some nodes, while you can also add a child node to others.
You can move the selected node up or down using the arrow icons.
You can also delete the node.

Click switch to source view to view the XML of the particular sequence. If you're familiar with the Synapse configuration language you can edit the XML directly.

Figure 5: Source view of the sequence editor

Field Descriptions

Core
Drop	Drops a particular message
Sequence	Defines a reference to an already defined sequence
Send	Sends the message to an endpoint defined inside the endpoint property. If an endpoint is not defined, sends the message to the address specified in the "to" header.
Log	Logs the received messages
Property	Handles message and transport level properties
Event	Send event notifications to an event source
Extension
Script	Defines a script in a scripting language and diverts control to that particular script
Class	Defines a reference to the Java class which implements the Mediator interface. Control will be passed to this class.
Spring	Defines a reference to a Spring bean which will take control
Command	Holds a reference to a class with only an execute method without having to implement the Mediator interface
Filter
Switch	Filters a message like in a switch case statement according to specified conditions
Filter	Filters a message like in an If Else clause
Out	Filters the outgoing messages
Validate	Validates a particular message over schema
In	Filters the incoming messages
Router	Route messages based on XPath filtering
Advanced
DBReport	Writes data to a database
Aggregate	Used for batch processing where a collection of messages gets treated as one
Clone	Makes copies of a message
Throttle	Throttle messages
Callout	Used to do a blocking call to a particular service
Iterate	Iterates over a set of message elements
DBLookup	Reads data from a database and gets it into a message
Cache	Caches response messages
Transaction	Executes a set of mediators transactionally
Rule	Rule based message mediation
Entitlement	Fine grained authentication
Transform
Fault	Creates a SOAP fault
Header	Processes message headers
XSLT	Transforms a particular message
XQuery	Transforms a message using XQuery

For more information please refer to the WSO2 library