The BPJ Library
From BP Wiki
See examples, e.g., BPJ/BPJCore110 -> bp.src.unittest.helloworld BPJ/Examples -> TicTacToe Events B-threads B-Program(s) A main method:
Contents
Events
- Reflect the elements of behavior of your application (and its environment) – what you want to see in a trace.
- Instantiate or extend Event class
- Optional string name in constructor or in setName();
- Optional data fields
- See later on Event Sets
B-Threads
- Contain the logic of your application
- You code runBThread() method
- Use events to affect system behavior
- Call bSync() method to request, wait for or block events
- You code import static bp.BProgram.bp
- Use Java freely – but don’t wait for slow things (GUI interaction should be done separately).
- Avoid or minimize side effects and external dependencies that are not event-driven
- Events should be natural system behavior - minimize usage of events for pure inter-b-thread communication.
- You may instantiate multiple instances of same b-thread class – possibly with constructor parameters
- Parameters may be manually specified during instantiation or generated by the application - see Tic-Tac-Toe example.
The B-Program
- A container and execution environment for b-threads.
- You only need to instantiate it.
- BProgram externalizes the public variable lastEvent that can be seen by b-threads.
- Usually – there is just one BProgram per application, running all your b-threads, but you may have several b-programs in parallel.
- You may change run-time parameters of the b-program by calling methods to set them.
The bSync() Method
- bSync(RequestableEventInterface,EventSetInterface,EventSetInterface)
- Three parameters:
- Requested Events:
- Waited-for events (a.k.a “watched events”)
- Blocked events
- Drives the collective execution mechanism:
- Synchronizes the b-thread with the others – waits until all b-threads call bSync().
- When all b-threads are waiting in bSync – the first event that is requested and is not blocked is selected. The search order is by b-thread priority, and within it – order of events in requestable event set.
- All b-threads that have the selected event in their requested events set or in their waited-for event set are resumed.
- B-threads can examine the event triggered by the last bSync in bp.lastEvent. Don’t modify this field; don’t rely on it past another bSync() call.
- This synchronization assumes that all b-threads will be good citizens and will not wait long (e.g., will not be involved in GUI input)
Event Sets and Interfaces
- The parameters to bSync are three sets of events, or sets of sets.
- Nesting of set containment is allowed, and not limited.
- RequestableEventInterface:
- Required for requested event parameter of bSync();
- Can be used also for watched and blocked.
- Must contain an ordered set of concrete events, or ordered sets of requestableEventInterface (nesting of sets).
- Implemented by RequestedEventsSet
- EventSetInterface:
- Can be used for waited-for and blocked events.
- Contains() method determines membership
- Can contain very large or infinite sets of events, or be used to filter events.
- Can contain eventSetInterface
- Is not sufficient as the requested events parameter of bSync()
- Implemented by EventSet
- RequestableEventSet: Implements both interfaces above
- EventSet: implements only EventSetInterface
- Event: The Event class implements the above interfaces. An individual event can be used instead of any of these sets. An event is also a set that contains the event.
Special Event Sets
- None: the empty set
- All: contains all events
- EventsOfClass: all events of a given class
- Composable event sets
- Available in BPJContrib (***?? What to do???)
- Allows specification of, e.g., theEventSet(A).and( not( theEventSet(B).or(C) ).xor( theEventSet(A).nand(c) ) )
anyOf( A, B, theEventSet(C).and(not(d)) )
The Application and the Main Method
- In the main method insert the line BProgram.startBApplication(my-app-class, my-package);
- In the method runBApplication you start the execution of your application
- Instantiate and add b-threads to the b-program
- Start the b-threads
- You must assign unique real number priority to each b-thread. The smaller the value, the higher the priority.
- runBApplication may exit, or may wait for all b-threads to end.
- Example (see BPJ package for more detail):
import static bp.BProgram.bp; public class my-app-class implements BApplication { public void runBApplication() bp.add(new my-Bthread-1(), mypriority1); bp.add(new my-Bthread-2(), mypriority2); … bp.startAll();
Dynamic B-Threads
- New b-threads may be added by external (non behavioral) applications modules, or by b-threads
- A running Java thread may be registered as a b-thread and subsequently deregistered as follows:...
See examples in...
Injecting External Events
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