Understanding and Utilizing the WSO2 ESB Property Mediator
The WSO2 Enterprise Service Bus (ESB) Property Mediator is a versatile tool used to manage and manipulate message properties within the mediation flow. This mediator allows you to set, retrieve, or remove properties that can be leveraged for various purposes such as routing, filtering, or modifying messages based on specific criteria.
Key Features of the Property Mediator
Setting Properties
The Property Mediator enables you to set properties at different scopes, including axis2, transport, or message, which can influence how messages are processed. You can also use these properties for dynamic message handling based on conditions or expressions.
Retrieving Properties
With the Property Mediator, you can read the value of properties that have been previously set, allowing for dynamic and flexible handling of messages. This is particularly useful in scenarios where you need to make real-time decisions based on message properties.
Removing Properties
The Property Mediator also provides the functionality to delete properties when they are no longer needed. This helps in maintaining a clean message context and ensures that unnecessary properties do not clutter the message context.
How to Use the Property Mediator
Step-by-Step Guide
Here’s a step-by-step guide on how to use the Property Mediator in a WSO2 ESB configuration:
Add the Property Mediator
In your mediation sequence, you can add a Property Mediator by selecting it from the list of available mediators.
Configure the Mediator
You need to configure the mediator with the following details:
Action: Choose whether to set, get, or remove a property. Name: Specify the name of the property. Value: If you are setting a property, provide the value. This can be a static value or a dynamic expression using XPath or JSONPath. Scope: Define the scope of the property, such as default, axis2, transport, or message.Example Configuration
Example Configuration in XML Format:
property name"myProperty" value"myValue" scope"default"
In this example, a property named myProperty is set with a value of myValue in the default scope. This property can be used in subsequent mediators for various purposes such as filtering or routing messages based on its value.
Using the Property
After setting a property, you can use it in subsequent mediators. For example, you might want to route a message based on the value of the property:
Example Using Property in a Filter:
filter xpath"//property[@name'myProperty']" value"myValue" scope"default"> then !-- Actions if the condition is true -- /then else !-- Actions if the condition is false -- /else
This filter will route the message to the specified path if the value of the property myProperty is myValue.
Testing
After configuring the Property Mediator, test your mediation flow to ensure that properties are being set, retrieved, and used correctly. This helps in identifying any issues early in the development process.
Best Practices
Use Descriptive Names
For better readability and maintenance, use descriptive names for your properties. This makes it easier for team members to understand the purpose of each property and maintain the code effectively.
Scope Management
Be mindful of the scope you choose as it affects the visibility and lifecycle of the properties. Incorrect scope settings can lead to issues such as properties not being accessible or being cleaned up prematurely.
Cleanup
Remove properties that are no longer needed to avoid cluttering the message context. This ensures that only relevant properties are present, which can improve performance and maintainability.
By effectively using the Property Mediator, you can enhance the flexibility and functionality of your mediation logic in WSO2 ESB. This tool is invaluable for building robust and dynamic mediation flows that can handle complex business scenarios.