16.58. Connector Terminology

A connector is the runnable code packaged in one or more JAR files that contains implementations of several interfaces (described below). A Java developer writes a connector to a type of source, such as a particular database management system, LDAP directory, or source code management system. It is then packaged into one or more JAR files (including dependent JARs) and deployed for use in applications that use ModeShape repositories.

The description of a particular source system (e.g., the "Customer" database, or the company LDAP system) is called a repository source. ModeShape provides a RepositorySource interface providing various features (including a method for establishing connections). A connector will have a class that implements this interface and that has JavaBean properties for all of the connector-specific properties required to describe an instance of the system. Use of JavaBean properties is not required, but it is recommended, as it enables reflective configuration and administration. Applications using ModeShape create an instance of the connector's RepositorySource and set the properties for the external source (that the application wants to access) with that connector.

A RepositorySource instance is then used to establish connections to that source. A connector provides an implementation of the RepositoryConnection interface, which defines methods for interacting with the external system. In particular, the execute(...) method takes an ExecutionContext instance and a Request object. The ExecutionContext object defines the environment in which the processing is occurring, while the Request object describes the requested operations on the content, with different subclasses representing each type of activity. Examples of commands include getting a node, moving a node, creating a node, changing a node, and deleting a node. If the repository source is able to participate in JTA/JTS distributed transactions, then the RepositoryConnection must implement the getXaResource() method by returning a valid javax.transaction.xa.XAResource object that can be used by the transaction monitor.