/*
* Copyright 2013 Stefan Domnanovits
*
* 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 com.codebullets.sagalib.processing;
import com.codebullets.sagalib.Saga;
import com.codebullets.sagalib.startup.MessageHandler;
import com.codebullets.sagalib.startup.SagaAnalyzer;
import com.codebullets.sagalib.startup.SagaHandlersMap;
import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import javax.inject.Inject;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Map;
import java.util.Objects;
import static com.google.common.base.Objects.toStringHelper;
/**
* Invokes the target handler on the provided saga for the given handler.
*/
public class ReflectionInvoker implements HandlerInvoker {
private static final Logger LOG = LoggerFactory.getLogger(ReflectionInvoker.class);
private final LoadingCache<InvokerKey, Method> methodInvokers;
/**
* Generates a new instance of ReflectionInvoker.
*/
@Inject
public ReflectionInvoker(final SagaAnalyzer analyzer) {
methodInvokers = CacheBuilder.newBuilder().build(new MethodSearcher(analyzer.scanHandledMessageTypes()));
}
/**
* {@inheritDoc}
*/
@Override
public void invoke(final Saga saga, final Object message) throws InvocationTargetException, IllegalAccessException {
InvokerKey key = InvokerKey.create(saga, message);
Method method = tryGetMethod(key);
if (method != null) {
method.invoke(saga, message);
} else {
LOG.warn("No method found to call. key = {}}", key);
}
}
/**
* Finds the method to invoke without causing an exception.
*/
private Method tryGetMethod(final InvokerKey key) {
Method methodToInvoke = null;
try {
methodToInvoke = methodInvokers.get(key);
} catch (Exception ex) {
LOG.warn("Error fetching method to invoke method {}", key, ex);
}
return methodToInvoke;
}
/**
* Searches for a specific handler method in the scanned map of handlers.
*/
private static class MethodSearcher extends CacheLoader<InvokerKey, Method> {
private final Map<Class<? extends Saga>, SagaHandlersMap> handlersMapMap;
public MethodSearcher(final Map<Class<? extends Saga>, SagaHandlersMap> handlersMapMap) {
this.handlersMapMap = handlersMapMap;
}
@Override
public Method load(final InvokerKey key) throws Exception {
Method methodToInvoke = null;
SagaHandlersMap handlers = handlersMapMap.get(key.getSagaClass());
if (handlers != null) {
for (MessageHandler handler : handlers.messageHandlers()) {
if (handler.getMessageType().equals(key.getMsgClass())) {
methodToInvoke = handler.getMethodToInvoke();
break;
}
}
}
return methodToInvoke;
}
}
/**
* Combined key of saga type and message being handled.
*/
private static class InvokerKey {
private final Class sagaClazz;
private final Class msgClazz;
public InvokerKey(final Class sagaClazz, final Class msgClazz) {
this.sagaClazz = sagaClazz;
this.msgClazz = msgClazz;
}
private Class getSagaClass() {
return sagaClazz;
}
private Class getMsgClass() {
return msgClazz;
}
@Override
public int hashCode() {
return Objects.hash(sagaClazz, msgClazz);
}
@Override
public boolean equals(final Object obj) {
boolean isEqual = false;
if (obj instanceof InvokerKey) {
InvokerKey other = (InvokerKey) obj;
isEqual = Objects.equals(msgClazz, other.msgClazz)
&& Objects.equals(sagaClazz, other.sagaClazz);
}
return isEqual;
}
public static InvokerKey create(final Saga sagaInstance, final Object msgInstance) {
return new InvokerKey(sagaInstance.getClass(), msgInstance.getClass());
}
@Override
public String toString() {
return toStringHelper(this)
.add("saga", sagaClazz)
.add("msg", msgClazz)
.toString();
}
}
}