Introduction to Message Translator
Translator will basically change the context of a message from one interface to another so that the message passed will adhere to the message context rules of the back end service. When communicating between several applications, each application might use a different data type or format. In order to successfully maintain the communication, messages need to be translated intermediately to a data format which will be compatible by the receiving application.
Message Translator is responsible for translating a message to ensure compatibility between applications supporting different data types. For more information please refer http://www.eaipatterns.com/MessageTranslator.html
Figure 1: Message Translator EIP
Example Scenario for the EIP
The rest of this document explains, through a typical example scenario, how the Content-Based Router EIP can be simulated using the WSO2 ESB.
The example scenario depicts an inventory for stocks and illustrates how the sender sends a request in a particular format that will be transformed into a format which is compatible with the receiver. In the given scenario the sender sends a request which contains the following format,
The format which is expected by the receiver is in the following format,
The scenario explains on how the message can be translated through the WSO2 ESB to a format which is compatible by the receiving application.
Implementing the Example Scenario in WSO2 ESB
The diagram below depicts how to simulate the example scenario using the WSO2 ESB.
Before digging into implementation details, let's take a look at the co-relation of the example scenario and the Content-Based Router EIP by comparing their core components.
|Figure 1: Content-Based Router EIP||Figure 2: Content-Based Router Example Scenario|
|Stock Quote Request|
|The translation is done through the Payload Factory Mediator|
1. Download an install the WSO2 ESB from http://wso2.com/products/enterprise-service-bus. For a list of prerequisites and step-by-step installation instructions, refer to Installation Guide in the WSO2 ESB documentation.
2. Start an instance of Axis2 server. For instructions, refer to section ESB Samples Setup - Starting Sample Back-End Services in the WSO2 ESB Documentation.
3. Start the WSO2 ESB and copy the following configuration to the "Source View" in the management console (Main Menu -> Service Bus -> Source View), using which the example scenario can be explored.
Simulating the Sample Scenario
4. Send a request using a SOAP request client (ex :- SOAP UI) to WSO2 ESB in the following manner,
When the above request was sent to the ESB through the client. the client will be able to notice that the request was successfully generated in the stock quote server.
How the Implementation Works
Let's investigate the elements of the ESB configuration in detail. The line numbers below are mapped with the ESB configuration illustrated in step 3 above.
- main sequence - The default sequence which will trigger when the user invokes the ESB server
- in - Once the message is hit in the main sequence the message will be diverted into the 'in'
- out - Will be triggered after execution of steps defined through the 'in'
- payload factory - Will transform the message to a format denoted within the mediator