WSO2 ESB usage of get-property function

What are Properties?

WSO2 has a huge set of mediators but property mediator is mostly used mediator for writing any proxy service or API.

Property mediator is used to store any value or xml fragment temporarily during life cycle of a thread for any service or API.

We can compare “Property” mediator with “Variable” in any other traditional programming languages (Like: C, C++, Java, .Net etc).

There are few properties those are used/maintained by ESB itself and on the other hand few properties can be defined by users (programmers). In other words, we can say that properties can be define in below 2 categories:

• ESB Defined Properties
• User Defined Properties.

These properties can be stored/defined in different scopes, like:

• Transport
• Synapse or Default
• Axis2
• Registry
• System
• Operation

Generally, these properties are read by get-properties() function. This function can be invoked with below 2 variations.

• get-property(String propertyName)
• get-property(String scope, String propertyName)

1st function doesn’t require to pass scope parameter, which always reads propetries from default/synapse scope.

Performance Hit (Found in WSO2 ESB 4.9.0 and prior versions):

It has been discovered that use of get-properties() function degrades performance drastically for any service.

Why it happens?

Get-Properties() function first does ESB Registry look-up and then later on difference scopes, however, using scope identifiers limits its search to the relevant area only.

Solution (Scope-Style Reading):

Instead of using get-properties() function these properties can be referenced by below prefixes separated by colon

• $ctx – from Synapse or Default Scope
• $trp – from Transport scope
• $axis2 – from Axis2 Scope
• $Header – Anything from Header
• $body – for accessing any element in SOAP Body (applicable for SOAP 1.1 and SOAP 1.2)

Example:

Lets assume that there is any property set with name “Test-Property”

From Default Scope

<property name=”Read-Property-value” expression=”get-property(‘Test-Property’)”/>

<property name=”Read-Property-value” expression=”$ctx:Test-Property”/>

From Transport Scope

<property name=”Read-Property-value” expression=”get-property(‘transport’,’Test-Property’)”/>

<property name=”Read-Property-value” expression=”$trp:Test-Property”/>

From Axis2 Scope

<property name=”Read-Property-value” expression=”get-property(‘axis2′,’Test-Property’)”/>

<property name=”Read-Property-value” expression=”$axis2:Test-Property”/>

We should prefer to use blue colour format for accessing these properties for better performance.

Please note this syntax is not applicable for few ESB defined properties, like: OperationName, MessageID, To
It will work as expected with get-properties, but not with $ctx.

So, please make sure you are using correct way for accessing ESB define properties.