1. Stateful Aspects in JAsCo
Wim Vanderperren
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2. Natural Evolution of joinpoints:
Stateful Aspects
Natural Evolution of joinpoints:
Static
Dynamic (e.g. cflow)
Stateful
Stateful Aspects in JAsCo
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3. Timing Aspect 1 class DynamicTimer {
3 private Vector<TimeListener> listeners = new Vector<TimeListener>();
4 private long timestampbefore, timestampafter;
6 void addTimeListener(TimeListener aListener) {
listeners.add(aListener);
8 }
9 void removeTimeListener(TimeListener aListener) {
listeners.remove(aListener);
11 }
12 void notifyTimeListeners(Method method, long time) {
for (TimeListener listener : listeners) {
listener.timeStampTaken(method,time); }
16 }
18 hook TimeStamp {
TimeStamp(timedmethod(..args)) {
execution(timedmethod); }
before {
timestampbefore = System.currentTimeMillis(); }
after {
timestampafter = System.currentTimeMillis();
notifyListeners(thisJointPoint,timestampafter-timestampbefore); }
29 }
30 }
Stateful Aspects in JAsCo
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4. Timing one method:
But how to time a protocol? E.g. time between execution of a-b-c on ComponentX.
1 connector TimeConnector {
2 DynamicTimer.TimeStamp timer =
new DynamicTimer.TimeStamp (void ComponentX.a());
4 timer.before();
5 timer.after();
6 }
Stateful Aspects in JAsCo
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5. Protocol Timing Aspect?
1 class ProtocolDynamicTimer extends DynamicTimer { 2
3 boolean methodaexecuted, methodbexecuted = false; 4
5 hook ProtocolMethodA {
ProtocolMethodA(methodA(..args)) {
execution(methodA); }
before {
timestampbefore = System.currentTimeMillis();
methodaexecuted = true; }
isApplicable() { return !methodaexecuted; }
15 } 16
17 hook ProtocolMethodB {
ProtocolMethodB(methodB(..args)) {
execution(methodB); }
before {
methodbexecuted = true; }
isApplicable() { return methodaexecuted; }
25 } 26
27 hook ProtocolMethodC {
ProtocolMethodC(methodC(..args)) {
execution (methodC); }
after {
timestampafter = System.currentTimeMillis();
notifyListeners(method,timestampafter-timestampbefore);
methodaexecuted = false; methodbexecuted = false; }
isApplicable() { return methodbexecuted; }
37 }
39 }
connector TimeConnector {
DynamicTimer.ProtocolMethodA timera =
new DynamicTimer. ProtocolMethodA (void ComponentX.a());
DynamicTimer.ProtocolMethodB timerb =
new DynamicTimer. ProtocolMethodB (void ComponentX.b());
DynamicTimer.ProtocolMethodC timerc =
new DynamicTimer. ProtocolMethodC (void ComponentX.c()); }
Stateful Aspects in JAsCo
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6. Stateful Aspects: Motivation
Protocol based aspects are rarely supported in current AOSD approaches (apart cflow).
Result: protocol checking code is scattered over advices, poluting advice code…
Is also not optimal, checks at all possible joinpoints while only a subset is required.
Stateful Aspects in JAsCo
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7. Example: Realize a more general protocol history condition than cflow.
Stateful Aspects
Allows specifying regular (=DFA based) hook triggering conditions in a hook’s constructor.
Advices can be attached to any transition of the DFA, or all of them (global).
Example: Realize a more general protocol history condition than cflow.
Stateful Aspects in JAsCo
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8. Timing Example Revisited
1 class ProtocolDynamicTimer extends DynamicTimer { 2
3 hook StatefulProtocolTimer { 4
long timestamp; 6
StatefulProtocolTimer(methodA(..args),methodB(..args),methodC(..args)) {
ATrans: execution(methodA) > BTrans;
BTrans: execution(methodB) > CTrans;
CTrans: execution(methodC) > ATrans; } 12
before ATrans() {
timestamp=System.currentTimeMillis(); }
after CTrans() {
long resultingtime = System.currentTimeMillis();
notifyListeners(calledmethod,resultingtime-timestamp); } 20
21 }
22 }
Regular JAsCo Pointcuts for triggering the transition
Transition Labels
Stateful Pointcut
Following Transitions to evaluate
Attaching Advices to specific transitions
Stateful Aspects in JAsCo
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9. Timing Example Revisited
static connector TimingConnector {
perthread ProtocolDynamicTimer.StatefulProtocolTimer timer =
new ProtocolDynamicTimer.StatefulProtocolTimer(
void ComponentX.a().,
void ComponentX.b(),
void ComponentX.c() ); }
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10. Advanced Pointcut Features
Explicit start transitions
start > XTrans;
Starting with two transitions:
start > XTrans || QTrans;
two destination transitions:
XTrans: execution(methodA) > YTrans || QTrans;
no destination transition
QTrans: execution(methodB) && !cflow(methodC);
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11. Advices
Multiple specific advices possible, one for each transition per before/around */after *
Global advice works for all transitions
isApplicable can also be global or specific
isApplicable() { //global condition for all transitions
// returns true if advices should be executed }
isApplicable XTrans() { //local condition only relevant for the transition XTrans
// returns true if advices should be executed for the XTrans transition
advantages
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12. Strict Protocols
Per default, stateful aspects are non-strict, e.g. protocol a()-d()-b()-c() also matches timing aspect.
When no intermediate transitions are allowed, use the strict keyword:
strict:
ATrans: execution(methodA) > BTrans;
BTrans: execution(methodB) > CTrans;
CTrans: execution(methodC) > ATrans;
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13. Strict Protocols with Context
Only strict with respect to a certain set of joinpoints. E.g. timing aspect does not accept intermediate transitions on ComponentX, on other classes is ok though.
StatefulProtocolTimer(methodA(..args),methodB(..args),methodC(..args), context(..args)) {
strict[execution(context)]:
ATrans: execution(methodA) > BTrans;
BTrans: execution(methodB) > CTrans;
CTrans: execution(methodC) > ATrans; }
Rejects:
ComponentX.a()
ComponentX.d()
ComponentX.b()
ComponentX.c()
static connector TimingConnector {
…. new ProtocolDynamicTimer.StatefulProtocolTimer(
void ComponentX.a().,
void ComponentX.b(),
void ComponentX.c(),
void ComponentX.*(*) ); }
Accepts:
ComponentX.a()
Y.d()
ComponentX.b()
ComponentX.c()
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14. Complement of a protocol
Trigger advices on everything outside the protocol: COMPLEMENT
StatefulProtocolTimer(methodA(..args),methodB(..args),methodC(..args)) {
complement:
ATrans: execution(methodA) > BTrans;
BTrans: execution(methodB) > CTrans;
CTrans: execution(methodC) > ATrans; }
around complement() {
throw new SecurityException(“this is not allowed on “+thisJoinPoint.getClass());
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15. Complement with Context
Only complement with respect to a certain set of joinpoints.
StatefulProtocolTimer(methodA(..args),methodB(..args),methodC(..args), context(..args)) {
complement[execution(context)]:
ATrans: execution(methodA) > BTrans;
BTrans: execution(methodB) > CTrans;
CTrans: execution(methodC) > ATrans; }
d() in complement:
ComponentX.a()
ComponentX.d()
ComponentX.b()
ComponentX.c()
static connector TimingConnector {
…. new ProtocolDynamicTimer.StatefulProtocolTimer(
void ComponentX.a().,
void ComponentX.b(),
void ComponentX.c(),
void ComponentX.*(*) ); }
No complement:
ComponentX.a()
Y.d()
ComponentX.b()
ComponentX.c()
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16. Default: weaved at all possible joinpoints defined in the pointcut.
Weaving
A DFA (Deterministic Finite Automaton) executes the stateful aspect at run-time.
Default: weaved at all possible joinpoints defined in the pointcut.
Optionally, jumping aspect in cooperation with run-time weaver:
only weaved at next joinpoints in protocol
overhead of reweaving vs overhead of aspect applied at all
Stateful Aspects in JAsCo
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