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org.requirementsascode.ModelRunner Maven / Gradle / Ivy
Enables you to define and run executable use case specifications, in your code.
package org.requirementsascode;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Objects;
import java.util.Optional;
import java.util.Set;
import java.util.function.Consumer;
import java.util.function.Predicate;
import org.requirementsascode.exception.InfiniteRepetition;
import org.requirementsascode.exception.MissingUseCaseStepPart;
import org.requirementsascode.exception.MoreThanOneStepCanReact;
import org.requirementsascode.exception.NestedCallOfReactTo;
/**
* A model runner is a highly configurable controller that receives messages and
* conditionally calls methods that handle them (the "system reactions").
*
*
* The runner is configured by the model it owns. Each real user needs an
* instance of a runner, as the runner determines the user journey.
*/
public class ModelRunner {
private static final Class SYSTEM_EVENT_CLASS = ModelRunner.class;
private AbstractActor owningActor;
private AbstractActor runActor;
private Model model;
private Step latestStep;
private Object latestPublishedEvent;
private boolean isRunning;
private StepToBeRun stepToBeRun;
private Consumer messageHandler;
private Consumer unhandledMessageHandler;
private Consumer messagePublisher;
private List recordedStepNames;
private List recordedMessages;
private boolean isRecording;
private boolean nestedReactToMessageCallCausesException;
/**
* Constructor for creating a model runner.
*/
public ModelRunner() {
handleWith(this::runStep);
publishWith(this::publishMessage);
}
private void runStep(StepToBeRun stepToBeRun) {
stepToBeRun.run();
}
private void publishMessage(T message) {
Optional optionalToActor = getLatestStep().flatMap(ls -> ls.getPublishTo());
nestedReactToMessageCallCausesException = false;
if(optionalToActor.isPresent()) {
AbstractActor owningActor = getOwningActor().orElse(model.getUserActor());
optionalToActor.get().reactTo(message, owningActor);
}else {
this.reactToMessage(message);
}
}
/**
* Define a custom message handler. It can perform tasks before/after running the
* step (which will trigger the system reaction method defined in the model).
*
* A custom message handler is useful for cross-cutting concerns, e.g. measuring
* performance.
*
* @param messageHandler the custom message handler
* @return this model runner, for chaining
*/
public ModelRunner handleWith(Consumer messageHandler) {
this.messageHandler = Objects.requireNonNull(messageHandler);
return this;
}
/**
* Define handler for messages that the runner doesn't react to.
*
* @param unhandledMessageHandler the handler for messages not handled by the runner
* @return this model runner, for chaining
*/
public ModelRunner handleUnhandledWith(Consumer unhandledMessageHandler) {
this.unhandledMessageHandler = Objects.requireNonNull(unhandledMessageHandler);
return this;
}
/**
* Define a custom publisher for events. It will be called after a system
* reaction has been run, for the returned event objects of the system
* reaction.
*
* @param eventPublisher the custom event eventPublisher
* @return this model runner, for chaining
*/
public ModelRunner publishWith(Consumer eventPublisher) {
Objects.requireNonNull(eventPublisher);
this.messagePublisher = event -> {
if(isRunning) {
setLatestPublishedEvent(event);
eventPublisher.accept(event);
}
};
return this;
}
/**
* Restarts the runner, resetting it to its original defaults ("no flow has been
* run, no step has been run").
*/
public void restart() {
setLatestStep(null);
run(model);
}
/**
* Configures the runner to use the specified model. After you called this
* method, the runner will accept messages via {@link #reactTo(Object)}.
*
*
* As a side effect, this method immediately triggers "autonomous system
* reactions".
*
* @param model the model that defines the runner's behavior
* @return this model runner, for chaining
*/
public ModelRunner run(Model model) {
AbstractActor userActor = model.getUserActor();
as(userActor).run(model);
return this;
}
/**
* After you called this method, the runner will only react in steps that have
* explicitly set the specified actor as one of its actors, or that are declared
* as "autonomous system reactions".
*
* @param runActor the actor to run as
* @return object for method chaining
*/
public As as(AbstractActor runActor) {
return new As(runActor);
}
public class As{
private As(AbstractActor runActor) {
setRunActor(runActor);
}
public ModelRunner run(Model model) {
return runModel(model);
}
public Optional reactTo(T message) {
return ModelRunner.this.reactTo(message);
}
public Optional reactTo(Object... messages) {
return ModelRunner.this.reactTo(messages);
}
}
private ModelRunner runModel(Model model) {
setModel(model);
initializeStepToBeRun();
setRunning(true);
triggerAutonomousSystemReaction();
return this;
}
private void triggerAutonomousSystemReaction() {
nestedReactToMessageCallCausesException = false;
reactToMessage(this);
}
/**
* Returns whether the runner is currently running.
*
* @see #run(Model)
* @return true if the runner is running, false otherwise.
*/
public boolean isRunning() {
return isRunning;
}
/**
* Stops the runner. It will not be reacting to messages, until
* {@link #run(Model)} is called again.
*/
public void stop() {
setRunning(false);
}
/**
* Call this method to provide several messages to the runner. For each message,
* {@link #reactTo(Object)} is called.
*
* @param the return type that you as the user expects.
*
* @param messages the message objects
* @return the event that was published (latest) if the system reacted, or an
* empty Optional.
*/
@SuppressWarnings("unchecked")
public Optional reactTo(Object... messages) {
Objects.requireNonNull(messages);
clearLatestPublishedEvent();
for (Object message : messages) {
reactToMessage(message);
}
return Optional.ofNullable((U) latestPublishedEvent);
}
/**
* Call this method to provide a message (i.e. command or event object) to the
* runner.
*
*
* If it is running, the runner will then check which steps can react. If a
* single step can react, the runner will call the message handler with it. If
* no step can react, the runner will either call the handler defined with
* {@link #handleUnhandledWith(Consumer)}, or if no such handler exists, consume
* the message silently.
*
* If more than one step can react, the runner will throw an exception.
*
*
* After that, the runner will trigger "autonomous system reactions".
*
* Note that if you provide a collection as the first and only argument, this
* will be flattened to the objects in the collection, and for each object
* {@link #reactTo(Object)} is called.
*
*
* See {@link #canReactTo(Class)} for a description of what "can react" means.
*
* @param the type of message
* @param the return type that you as the user expects.
* @param message the message object
* @return the event that was published (latest) if the system reacted, or an empty Optional.
* @throws MoreThanOneStepCanReact when more than one step can react
* @throws InfiniteRepetition when a step has an always true condition, or
* there is an infinite loop.
* @throws ClassCastException when type of the returned instance isn't U
*/
@SuppressWarnings("unchecked")
public Optional reactTo(T message) {
Objects.requireNonNull(message);
if (message instanceof Collection) {
Object[] messages = ((Collection) message).toArray(new Object[0]);
return reactTo(messages);
}
clearLatestPublishedEvent();
reactToMessage(message);
return Optional.ofNullable((U)latestPublishedEvent);
}
private void reactToMessage(T message) {
if (!isRunning) {
return;
}
if(nestedReactToMessageCallCausesException) {
throw new NestedCallOfReactTo();
}
Class currentMessageClass = message.getClass();
try {
int nrOfStepsThatCanReact = 0;
Step stepThatWillReact = null;
Collection steps = model.getModifiableSteps();
for (Step step : steps) {
if (canReactToMessageClass(step, currentMessageClass)) {
stepThatWillReact = step;
nrOfStepsThatCanReact++;
if (nrOfStepsThatCanReact > 1) {
// No more than one step is allowed to react to a message
throw new MoreThanOneStepCanReact(steps);
}
}
}
if (nrOfStepsThatCanReact == 1) {
triggerSystemReaction(message, stepThatWillReact);
} else if (unhandledMessageHandler != null && !isSystemEvent(message)) {
unhandledMessageHandler.accept(message);
} else if (message instanceof RuntimeException) {
throw (RuntimeException) message;
}
} catch (StackOverflowError err) {
throw new InfiniteRepetition(latestStep);
}
}
private boolean canReact(Step step) {
boolean stepCanReact = hasRightActor(step) && hasTruePredicate(step);
return stepCanReact;
}
boolean canReactToMessageClass(Step step, Class currentMessageClass) {
boolean stepCanReact = stepMessageClassIsSameOrSuperclass(step, currentMessageClass) && canReact(step);
return stepCanReact;
}
private boolean hasRightActor(Step step) {
final Predicate isSystemOrRunActor = actor -> actor.equals(model.getUserActor())
|| actor.equals(model.getSystemActor()) || actor.equals(runActor);
AbstractActor[] stepActors = step.getActors();
if (stepActors == null) {
throw (new MissingUseCaseStepPart(step, "actor"));
}
for (AbstractActor stepActor : stepActors) {
if (isSystemOrRunActor.test(stepActor)) {
return true;
}
}
return false;
}
private boolean stepMessageClassIsSameOrSuperclass(Step step, Class currentMessageClass) {
Class stepMessageClass = step.getMessageClass();
if (stepMessageClass == null) {
throw new MissingUseCaseStepPart(step, "on/user");
}
boolean result = hasSystemEventClass(currentMessageClass)? hasSystemEventClass(stepMessageClass)
: stepMessageClass.isAssignableFrom(currentMessageClass);
return result;
}
private boolean hasTruePredicate(Step step) {
Predicate predicate = step.getPredicate();
boolean result = predicate.test(this);
return result;
}
private void triggerSystemReaction(Object message, Step step) {
if (step.getSystemReaction() == null) {
throw new MissingUseCaseStepPart(step, "system");
}
stepToBeRun.setupWith(step, message);
recordStepNameAndMessage(step, message);
setLatestStep(step);
try {
nestedReactToMessageCallCausesException = true;
Condition isTheCase = step.getCase().orElse(() -> true);
if (isTheCase.evaluate()) {
messageHandler.accept(stepToBeRun);
publishReturnedMessage();
}
} catch (Exception e) {
handleException(e);
}
triggerAutonomousSystemReaction();
}
private void publishReturnedMessage() {
Optional messageToBePublished = stepToBeRun.getMessageToBePublished();
if(messagePublisher != null && messageToBePublished.isPresent()) {
messagePublisher.accept(messageToBePublished.get());
}
}
private boolean isSystemEvent(T message) {
return hasSystemEventClass(message.getClass());
}
private boolean hasSystemEventClass(Class messageClass) {
return SYSTEM_EVENT_CLASS.equals(messageClass);
}
void recordStepNameAndMessage(Step step, Object message) {
if (isRecording) {
recordedStepNames.add(step.getName());
if (message != null) {
recordedMessages.add(message);
}
}
}
/**
* Returns whether at least one step can react to a message of the specified
* class.
*
* A step "can react" if all of the following conditions are met: a) the runner
* is running b) one of the step's actors matches the actor the runner is run as
* c) the step's message class is the same or a superclass of the specified message
* class d) the step has a condition that is true
*
* @param messageClass the type of message to check steps for
* @return true if the runner is running and at least one step can react, false
* otherwise
*/
public boolean canReactTo(Class messageClass) {
Objects.requireNonNull(messageClass);
if(!isRunning) {
return false;
}
boolean canReact = false;
Collection steps = model.getModifiableSteps();
for (Step step : steps) {
if (canReactToMessageClass(step, messageClass)) {
canReact = true;
break;
}
}
return canReact;
}
/**
* Returns the classes of messages the runner can react to.
*
* See {@link #canReactTo(Class)} for a description of what "can react" means.
*
* @return the collection of message types
*/
public Set> getReactToTypes() {
Set> reactToTypes;
if(isRunning) {
reactToTypes = new LinkedHashSet<>();
Collection steps = model.getModifiableSteps();
for (Step step : steps) {
if (canReact(step)) {
Class messageClass = step.getMessageClass();
reactToTypes.add(messageClass);
}
}
} else {
reactToTypes = Collections.emptySet();
}
return reactToTypes;
}
/**
* Returns the steps in the model that can react to the specified message class.
*
* @param messageClass the class of messages
* @return the steps that can react to the class of messages
*/
public Set getStepsThatCanReactTo(Class messageClass) {
Objects.requireNonNull(messageClass);
Set stepsThatCanReact = new HashSet<>(2);
if(isRunning) {
Collection steps = model.getModifiableSteps();
for (Step step : steps) {
if (canReactToMessageClass(step, messageClass)) {
stepsThatCanReact.add(step);
}
}
}
return stepsThatCanReact;
}
/**
* Overwrite this method to control what happens exactly when an exception is
* thrown by a system reaction. The behavior implemented in runner: the model
* runner reacts to the exception. You may replace this with a more
* sophisticated behavior, that for example involves some kind of logging.
*
* @param e the exception that has been thrown by the system reaction
*/
protected void handleException(Exception e) {
nestedReactToMessageCallCausesException = false;
reactToMessage(e);
}
/**
* Returns the latest step that has been run by this runner.
*
* @return the latest step run
*/
public Optional getLatestStep() {
return Optional.ofNullable(latestStep);
}
/**
* Sets the latest step run by the runner.
*
*
* Use this method if you want to restore some previous state, normally you
* should influence the behavior of the runner by calling
* {@link #reactTo(Object)}.
*
* @param latestStep the latest step run
*/
public void setLatestStep(Step latestStep) {
this.latestStep = latestStep;
}
/**
* Returns the flow the latest step that has been run is contained in.
*
* @return the latest flow run
*/
public Optional getLatestFlow() {
return getLatestStep().filter(step -> step instanceof FlowStep).map(step -> ((FlowStep) step).getFlow());
}
/**
* After calling this method, until recording is stopped, messages and step names
* are recorded. If messages/step names have been recorded before calling this
* method, they are discarded.
*
* @return this model runner for method chaining
*/
public ModelRunner startRecording() {
recordedStepNames = new ArrayList<>();
recordedMessages = new ArrayList<>();
isRecording = true;
return this;
}
/**
* When calling this method, recording is stopped. No messages and step names are
* recorded until {@link #startRecording()} is called again.
*
* @return this model runner for method chaining
*/
public ModelRunner stopRecording() {
isRecording = false;
return this;
}
/**
* Returns the recorded names of the steps that have been run so far.
*
* If no step has been run, an empty array is returned. For example, this method
* can used with the assertArrayEquals method of JUnit to compare the actual
* names of steps that have been run (returned by this method) to the expected
* step names.
*
* @return the ordered names of steps run by this runner
*/
public String[] getRecordedStepNames() {
if(recordedStepNames == null) {
recordedStepNames = new ArrayList<>();
}
String[] stepNames = recordedStepNames.stream().toArray(String[]::new);
return stepNames;
}
/**
* Returns the recorded messages that the runner reacted to so far.
*
* If no messages have caused a system reaction, an empty array is returned. For
* example, this method can used with the assertArrayEquals method of JUnit to
* compare the actual messages that caused a reaction (returned by this method) to
* the expected messages.
*
* @return the messages that caused a system reaction, in order of occurrence
*/
public Object[] getRecordedMessages() {
if(recordedMessages == null) {
recordedMessages = new ArrayList<>();
}
Object[] messages = recordedMessages.toArray();
return messages;
}
/**
* Returns the actor that owns this model runner for running its behavior.
*
* @return the owning actor, if existent, or an empty optional
*/
public Optional getOwningActor() {
return Optional.ofNullable(owningActor);
}
void setOwningActor(AbstractActor owningActor) {
this.owningActor = owningActor;
}
private void initializeStepToBeRun() {
this.stepToBeRun = new StepToBeRun();
}
private void setModel(Model model) {
this.model = Objects.requireNonNull(model);
}
private void setRunning(boolean status) {
isRunning = status;
}
private void setRunActor(AbstractActor runActor) {
this.runActor = Objects.requireNonNull(runActor);
}
private void clearLatestPublishedEvent() {
latestPublishedEvent = null;
}
private void setLatestPublishedEvent(Object event) {
latestPublishedEvent = event;
}
}
