In many enterprises, a single function is spread across several systems. In such situations, it is important to ensure that the message goes through each of the systems that contain the function. In such situations, the content-based router pattern becomes very helpful. The content-based router pattern is depicted as follows:

The content-based router pattern examines the content of the message and then routes the message onto the correct channel based on the data that is contained in the message. The parameters on which the message is routed could be one of the following:

• Existence of certain data values in specific fields
• Presence or absence of certain fields in the message

It is very important to ensure that in a content-based router, the routing function that is implemented in the router should be easy to maintain. It is also possible to maintain a content-based router in the form of a rules engine that calculates the destination channel based on a set of pre-configured rules.