How to use Dynamic Registry Keys with WSO2 ESB Mediators

From this post I will going to briefly introduce about one of the new features provided by WSO2 ESB. Earlier WSO2 ESB supported static registry keys where users can select a key for the mediator as a static value. But from ESB 4.0.0 users can use dynamic registry keys where users can define XPath expression to evaluate the registry key in run time.

For an example let's consider XSLT mediator. With earlier static registry key based method user have to define only single XSLT file for transformation. With the use of dynamic registry key, user will be able to use XPath expressions to dynamically generate the registry key, based on the message context. So with that user can have multiple XSLT files and based on the evaluated key mediator will be able to select the required XSLT file in run time.

Following is a sample usage of static and dynamic registry keys and user can use both of them according to situation.

 

1. Static Registry Key – define the exact path to find the xslt file like bellow.<xslt key="xslt-key-req"/>

Image1 : User can select static key from registry browser

      eg:

1: <sequence xmlns="http://ws.apache.org/ns/synapse" name="main">
2:     <in>
3:         <xslt key="conf:/repository/synapse/samples/transform/transform.xslt" />
4:     </in>
5:     <out>
6:         <xslt key="conf:/repository/synapse/samples/transform/transform_back.xslt" />
7:     </out>
8:     <send />
9: </sequence>

2. Dynamic Registry Key – Using an Xpath expression inside curly braces {  }, to identify the key like bellow.

Image2: User can add dynamic key inside { }. Also user can define NameSpaces as well.

      eg:

1: <xslt xmlns:ns="http://org.apache.synapse/xsd" xmlns:ns3="http://org.apache.synapse/xsd" key="{get-property('symbol')}" />
2: 
3: <sequence xmlns="http://ws.apache.org/ns/synapse" name="main">
4:    <in>
5:       <property name="symbol" value="conf:/repository/synapse/samples/transform/transform.xslt" />
6:       <xslt xmlns:ns="http://org.apache.synapse/xsd" xmlns:ns3="http://org.apache.synapse/xsd" key="{get-property('symbol')}" />
7:    </in>
8:    <out>
9:       <xslt key="conf:/repository/synapse/samples/transform/transform_back.xslt" />
10:    </out>
11:    <send />
12: </sequence>