Active Object an Object Behavioral Pattern for Concurrent Programming

This paper describes the Active Object pattern, which decouples method execution from method invocation in order to simplify synchronized access to a shared resource by methods invoked in different threads of control. The Active Object pattern allows one or more independent threads of execution to interleave their access to data modeled as a single object. A broad class of producer/consumer and reader/writer problems are well-suited to this model of concurrency. This pattern is commonly used in distributed systems requiring multi-threaded servers. In addition, client applications (such as windowing systems and network browsers), are increasingly employing active objects to simplify concurrent, asynchronous network operations.