Adapters are some combination of design tools and runtime software that act as glue to link applications, which are considered "sources" or "targets" (or both), to other applications or other integration middleware.
When interfacing with a source or target application, an adapter generally deals with a group of "touch points," that is, one or more entry/exit points, collectively called an "interface."
Adapters can be deceptively complex, with "thick" adapters performing a variety of functions that include recognizing events, collecting and transforming data, and exchanging data with platform, integration suite or other middleware. On the other hand, "thin" adapters may only "wrap" a native application interface, exposing another, more standard interface for application access. Adapters can also handle exception conditions, and can often dynamically (or with minor reconfiguration changes) accommodate new revisions of source or target applications.
Two common types of adapters are:
- Technical Adapters - Technical adapters may connect into Database Management Systems (DBMSs), communication middleware or other software environments. By definition, technical adapters are not inherently configured to be business process-aware.
- Application Adapters - Application adapters interface to packaged application modules or vertical-industry protocols (like HL7 or HIPAA). By definition, application adapters are inherently configured to interact with a source or target interface and read or write specific business documents or messages. Many application adapters include technical adapters within them. For example, an application adapter that is used to import or export purchase orders from a procurement application can leverage a technical adapter, which accesses the application at the database or low-level Application Program Interface (API) level. While the technical adapter could be licensed and used by itself, the value of the application adapter is that it eliminates the need for complex logic that is often necessary to navigate what are often complex database or low-level interfaces.
Adapters are generally bundled with integration middleware products such as Enterprise Service Buses (ESBs), integration suites, or portal servers; or offered as a stand-alone product such as an adapter suite. Ideally, every adapter, like most application integration tools, should be noninvasive, such that it can interact with the source or target without requiring any customization in the source or target. Such independence helps insulate the adapter from its source or target's upgrades — for example, for new versions of software.
