/*
* Copyright 2015-2017 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 org.springframework.amqp.rabbit.listener.adapter;
import java.lang.annotation.Annotation;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import org.springframework.amqp.AmqpException;
import org.springframework.amqp.support.AmqpHeaders;
import org.springframework.beans.factory.config.BeanExpressionContext;
import org.springframework.beans.factory.config.BeanExpressionResolver;
import org.springframework.core.MethodParameter;
import org.springframework.core.annotation.AnnotationUtils;
import org.springframework.expression.Expression;
import org.springframework.expression.ParserContext;
import org.springframework.expression.common.TemplateParserContext;
import org.springframework.expression.spel.standard.SpelExpressionParser;
import org.springframework.messaging.Message;
import org.springframework.messaging.handler.annotation.Payload;
import org.springframework.messaging.handler.annotation.SendTo;
import org.springframework.messaging.handler.invocation.InvocableHandlerMethod;
import org.springframework.util.Assert;
/**
* Delegates to an {@link InvocableHandlerMethod} based on the message payload type.
* Matches a single, non-annotated parameter or one that is annotated with {@link Payload}.
* Matches must be unambiguous.
*
* @author Gary Russell
* @since 1.5
*
*/
public class DelegatingInvocableHandler {
private static final SpelExpressionParser PARSER = new SpelExpressionParser();
private static final ParserContext PARSER_CONTEXT = new TemplateParserContext("!{", "}");
private final List<InvocableHandlerMethod> handlers;
private final ConcurrentMap<Class<?>, InvocableHandlerMethod> cachedHandlers =
new ConcurrentHashMap<Class<?>, InvocableHandlerMethod>();
private final Map<InvocableHandlerMethod, Expression> handlerSendTo =
new HashMap<InvocableHandlerMethod, Expression>();
private final Object bean;
private final BeanExpressionResolver resolver;
private final BeanExpressionContext beanExpressionContext;
/**
* Construct an instance with the supplied handlers for the bean.
* @param handlers the handlers.
* @param bean the bean.
* @param beanExpressionResolver the resolver.
* @param beanExpressionContext the context.
*/
public DelegatingInvocableHandler(List<InvocableHandlerMethod> handlers, Object bean,
BeanExpressionResolver beanExpressionResolver, BeanExpressionContext beanExpressionContext) {
this.handlers = new ArrayList<InvocableHandlerMethod>(handlers);
this.bean = bean;
this.resolver = beanExpressionResolver;
this.beanExpressionContext = beanExpressionContext;
}
/**
* @return the bean
*/
public Object getBean() {
return this.bean;
}
/**
* Invoke the method with the given message.
* @param message the message.
* @param providedArgs additional arguments.
* @return the result of the invocation.
* @throws Exception raised if no suitable argument resolver can be found,
* or the method raised an exception.
*/
public Object invoke(Message<?> message, Object... providedArgs) throws Exception {
Class<? extends Object> payloadClass = message.getPayload().getClass();
InvocableHandlerMethod handler = getHandlerForPayload(payloadClass);
Object result = handler.invoke(message, providedArgs);
if (message.getHeaders().get(AmqpHeaders.REPLY_TO) == null) {
Expression replyTo = this.handlerSendTo.get(handler);
if (replyTo != null) {
result = new AbstractAdaptableMessageListener.ResultHolder(result, replyTo);
}
}
return result;
}
/**
* @param payloadClass the payload class.
* @return the handler.
*/
protected InvocableHandlerMethod getHandlerForPayload(Class<? extends Object> payloadClass) {
InvocableHandlerMethod handler = this.cachedHandlers.get(payloadClass);
if (handler == null) {
handler = findHandlerForPayload(payloadClass);
if (handler == null) {
throw new AmqpException("No method found for " + payloadClass);
}
this.cachedHandlers.putIfAbsent(payloadClass, handler); //NOSONAR
setupReplyTo(handler);
}
return handler;
}
private void setupReplyTo(InvocableHandlerMethod handler) {
String replyTo = null;
Method method = handler.getMethod();
if (method != null) {
SendTo ann = AnnotationUtils.getAnnotation(method, SendTo.class);
replyTo = extractSendTo(method.toString(), ann);
}
if (replyTo == null) {
SendTo ann = AnnotationUtils.getAnnotation(this.bean.getClass(), SendTo.class);
replyTo = extractSendTo(this.getBean().getClass().getSimpleName(), ann);
}
if (replyTo != null) {
this.handlerSendTo.put(handler, PARSER.parseExpression(replyTo, PARSER_CONTEXT));
}
}
private String extractSendTo(String element, SendTo ann) {
String replyTo = null;
if (ann != null) {
String[] destinations = ann.value();
if (destinations.length > 1) {
throw new IllegalStateException("Invalid @" + SendTo.class.getSimpleName() + " annotation on '"
+ element + "' one destination must be set (got " + Arrays.toString(destinations) + ")");
}
replyTo = destinations.length == 1 ? resolve(destinations[0]) : null;
}
return replyTo;
}
private String resolve(String value) {
if (this.resolver != null) {
Object newValue = this.resolver.evaluate(value, this.beanExpressionContext);
Assert.isInstanceOf(String.class, newValue, "Invalid @SendTo expression");
return (String) newValue;
}
else {
return value;
}
}
protected InvocableHandlerMethod findHandlerForPayload(Class<? extends Object> payloadClass) {
InvocableHandlerMethod result = null;
for (InvocableHandlerMethod handler : this.handlers) {
if (matchHandlerMethod(payloadClass, handler)) {
if (result != null) {
throw new AmqpException("Ambiguous methods for payload type: " + payloadClass + ": " +
result.getMethod().getName() + " and " + handler.getMethod().getName());
}
result = handler;
}
}
return result;
}
protected boolean matchHandlerMethod(Class<? extends Object> payloadClass, InvocableHandlerMethod handler) {
Method method = handler.getMethod();
Annotation[][] parameterAnnotations = method.getParameterAnnotations();
// Single param; no annotation or @Payload
if (parameterAnnotations.length == 1) {
MethodParameter methodParameter = new MethodParameter(method, 0);
if (methodParameter.getParameterAnnotations().length == 0
|| methodParameter.hasParameterAnnotation(Payload.class)) {
if (methodParameter.getParameterType().isAssignableFrom(payloadClass)) {
return true;
}
}
}
boolean foundCandidate = false;
for (int i = 0; i < parameterAnnotations.length; i++) {
MethodParameter methodParameter = new MethodParameter(method, i);
if (methodParameter.getParameterAnnotations().length == 0
|| methodParameter.hasParameterAnnotation(Payload.class)) {
if (methodParameter.getParameterType().isAssignableFrom(payloadClass)) {
if (foundCandidate) {
throw new AmqpException("Ambiguous payload parameter for " + method.toGenericString());
}
foundCandidate = true;
}
}
}
return foundCandidate;
}
/**
* Return a string representation of the method that will be invoked for this payload.
* @param payload the payload.
* @return the method name.
*/
public String getMethodNameFor(Object payload) {
InvocableHandlerMethod handlerForPayload = getHandlerForPayload(payload.getClass());
return handlerForPayload == null ? "no match" : handlerForPayload.getMethod().toGenericString(); //NOSONAR
}
/**
* Return the method that will be invoked for this payload.
* @param payload the payload.
* @return the method.
* @since 2.0
*/
public Method getMethodFor(Object payload) {
InvocableHandlerMethod handlerForPayload = getHandlerForPayload(payload.getClass());
return handlerForPayload == null ? null : handlerForPayload.getMethod();
}
}