Role of Adapters in Integration Project
Adapters are endpoints of any integration solution, so they interact directly with the business applications. The role of adapters is defined by the type of integration scenarios. In the case of data integration scenarios, adapters are responsible for extracting data from the business applications database, and updating the application database with external data and actions. When the integration scenario is about workflow automation, adapters must enable applications to generate events representing application transaction and state changes in the database. Adapters also need to handle external events and triggers, which may require the application to take specific actions. In the scenario of Web services, adapters expose application functions to the Web and invoke appropriate application function, depending on the service request. It is usually a good practice to identify adapters with the business application it integrates instead of the integration platform it requires to achieve the integration. In other words, it is very important to understand that adapters are extensions of the business applications and not of the integration platform or infrastructure.
Project managers need to make a conscious decision to include application adapters in any type of integration scenario. If the existing adapter does not provide the functionality required for the integration scenario, the adapter must be upgraded. Following this practice ensures that all integration logic is located in one place (in the adapter), making future upgrades and maintenance in general easier. Without adapters, applications will have to be significantly changed.
Adapters do the actual connections with application resources (such as databases and middleware); and manage application transactions, security, exceptions, and so on. In an ideal integration scenario, all participating applications will have an adapter defining and managing the integration capability of the associated application. Adapters define the point of integration for an application, and hence project managers can build and share development metrics based on a known set of artifacts. The section "Estimating Adapter Development" provides some high-level guidelines on how to build adapter development and maintenance metrics.