/*
* Copyright 2011-2014 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package pl.com.bottega.ecommerce.system.saga.impl;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.Collection;
import javax.annotation.PostConstruct;
import javax.inject.Inject;
import javax.persistence.NoResultException;
import org.springframework.stereotype.Component;
import pl.com.bottega.ecommerce.system.infrastructure.events.SimpleEventPublisher;
import pl.com.bottega.ecommerce.system.infrastructure.events.impl.handlers.EventHandler;
import pl.com.bottega.ecommerce.system.saga.SagaEngine;
import pl.com.bottega.ecommerce.system.saga.SagaInstance;
import pl.com.bottega.ecommerce.system.saga.SagaManager;
import pl.com.bottega.ecommerce.system.saga.annotations.LoadSaga;
import pl.com.bottega.ecommerce.system.saga.annotations.SagaAction;
/**
* @author Rafał Jamróz
*/
@Component
public class SimpleSagaEngine implements SagaEngine {
private final SagaRegistry sagaRegistry;
private final SimpleEventPublisher eventPublisher;
@Inject
public SimpleSagaEngine(SagaRegistry sagaRegistry, SimpleEventPublisher eventPublisher) {
this.sagaRegistry = sagaRegistry;
this.eventPublisher = eventPublisher;
}
@PostConstruct
public void registerEventHandler() {
eventPublisher.registerEventHandler(new SagaEventHandler(this));
}
@SuppressWarnings({ "rawtypes", "unchecked" })
@Override
public void handleSagasEvent(Object event) {
Collection<SagaManager> loaders = sagaRegistry.getLoadersForEvent(event);
for (SagaManager loader : loaders) {
SagaInstance sagaInstance = loadSaga(loader, event);
invokeSagaActionForEvent(sagaInstance, event);
if (sagaInstance.isCompleted()) {
loader.removeSaga(sagaInstance);
}
}
}
@SuppressWarnings({ "rawtypes", "unchecked" })
private SagaInstance loadSaga(SagaManager loader, Object event) {
Class<? extends SagaInstance> sagaType = determineSagaTypeByLoader(loader);
Object sagaData = loadSagaData(loader, event);
if (sagaData == null) {
sagaData = loader.createNewSagaData();
}
SagaInstance sagaInstance = sagaRegistry.createSagaInstance(sagaType);
sagaInstance.setData(sagaData);
return sagaInstance;
}
// TODO determine saga type more reliably
@SuppressWarnings({ "rawtypes", "unchecked" })
private Class<? extends SagaInstance> determineSagaTypeByLoader(SagaManager loader) {
Type type = ((ParameterizedType) loader.getClass().getGenericInterfaces()[0]).getActualTypeArguments()[0];
return ((Class<? extends SagaInstance>) type);
}
/**
* TODO handle exception in more generic way
*/
@SuppressWarnings("rawtypes")
private Object loadSagaData(SagaManager loader, Object event) {
Method loaderMethod = findHandlerMethodForEvent(loader.getClass(), event);
try {
Object sagaData = loaderMethod.invoke(loader, event);
return sagaData;
} catch (InvocationTargetException e) {
// NRE is ok here, it means that saga hasn't been started yet
if (e.getTargetException() instanceof NoResultException) {
return null;
} else {
throw new RuntimeException(e);
}
} catch (Exception e) {
throw new RuntimeException(e);
}
}
private void invokeSagaActionForEvent(SagaInstance<?> saga, Object event) {
Method eventHandler = findHandlerMethodForEvent(saga.getClass(), event);
try {
eventHandler.invoke(saga, event);
} catch (Exception e) {
throw new RuntimeException(e);
}
}
private Method findHandlerMethodForEvent(Class<?> type, Object event) {
for (Method method : type.getMethods()) {
if (method.getAnnotation(SagaAction.class) != null || method.getAnnotation(LoadSaga.class) != null) {
if (method.getParameterTypes().length == 1
&& method.getParameterTypes()[0].isAssignableFrom(event.getClass())) {
return method;
}
}
}
throw new RuntimeException("no method handling " + event.getClass());
}
private static class SagaEventHandler implements EventHandler {
private final SagaEngine sagaEngine;
public SagaEventHandler(SagaEngine sagaEngine) {
this.sagaEngine = sagaEngine;
}
@Override
public boolean canHandle(Object event) {
return true;
}
@Override
public void handle(Object event) {
sagaEngine.handleSagasEvent(event);
}
}
}