Business logic plug-ins can be implemented as Java classes that perform specialized processing of business messages as those messages pass through an integration engine, such as a "B2B" engine for business-to-business messaging. Logic plug-ins can insert rules and business logic along the path traveled by business messages as they make their way through the B2B engine. Logic plug-ins can be defined and stored in an integration repository and executed in the B2B engine, and can be transparent to users. The plug-ins can utilize a plug-in framework, composed of a plug-in manager, as well as interfaces and mechanisms for plug-ins to implement. A plug-in manager can manage all plug-ins in the framework, can be a concrete implementation of the plug-in framework on the server, and can be a central hub through which all plug-in related client requests are routed.This description is not intended to be a complete description of, or limit the scope of, the invention. Other features, aspects, and objects of the invention can be obtained from a review of the specification, the figures, and the claims.