/**
* This Source Code Form is subject to the terms of the Mozilla Public License,
* v. 2.0. If a copy of the MPL was not distributed with this file, You can
* obtain one at http://mozilla.org/MPL/2.0/. OpenMRS is also distributed under
* the terms of the Healthcare Disclaimer located at http://openmrs.org/license.
*
* Copyright (C) OpenMRS Inc. OpenMRS is a registered trademark and the OpenMRS
* graphic logo is a trademark of OpenMRS Inc.
*/
package org.openmrs.util;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import java.util.Map;
import java.util.WeakHashMap;
import org.openmrs.annotation.Handler;
import org.openmrs.api.APIException;
import org.openmrs.api.context.Context;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.context.ApplicationListener;
import org.springframework.context.event.ContextRefreshedEvent;
import org.springframework.stereotype.Component;
/**
* Utility class that provides useful methods for working with classes that are annotated with the
* {@link Handler} annotation
*
* @since 1.5
*/
@Component
public class HandlerUtil implements ApplicationListener<ContextRefreshedEvent> {
private static final Logger log = LoggerFactory.getLogger(HandlerUtil.class);
private static volatile Map<Key, List<?>> cachedHandlers = new WeakHashMap<HandlerUtil.Key, List<?>>();
private static class Key {
public final Class<?> handlerType;
public final Class<?> type;
public Key(Class<?> handlerType, Class<?> type) {
this.handlerType = handlerType;
this.type = type;
}
@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + ((handlerType == null) ? 0 : handlerType.hashCode());
result = prime * result + ((type == null) ? 0 : type.hashCode());
return result;
}
@Override
public boolean equals(Object obj) {
if (this == obj) {
return true;
}
if (obj == null) {
return false;
}
if (getClass() != obj.getClass()) {
return false;
}
Key other = (Key) obj;
if (handlerType == null) {
if (other.handlerType != null) {
return false;
}
} else if (!handlerType.equals(other.handlerType)) {
return false;
}
if (type == null) {
if (other.type != null) {
return false;
}
} else if (!type.equals(other.type)) {
return false;
}
return true;
}
}
public static void clearCachedHandlers() {
cachedHandlers = new WeakHashMap<HandlerUtil.Key, List<?>>();
}
/**
* Retrieves a List of all registered components from the Context that are of the passed
* handlerType and one or more of the following is true:
* <ul>
* <li>The handlerType is annotated as a {@link Handler} that supports the passed type</li>
* <li>The passed type is null - this effectively returns all components of the passed
* handlerType</li>
* </ul>
* The returned handlers are ordered in the list based upon the order property.
*
* @param handlerType Indicates the type of class to return
* @param type Indicates the type that the given handlerType must support (or null for any)
* @return a List of all matching Handlers for the given parameters, ordered by Handler#order
* @should return a list of all classes that can handle the passed type
* @should return classes registered in a module
* @should return an empty list if no classes can handle the passed type
*/
public static <H, T> List<H> getHandlersForType(Class<H> handlerType, Class<T> type) {
List<?> list = cachedHandlers.get(new Key(handlerType, type));
if (list != null) {
return (List<H>) list;
}
List<H> handlers = new ArrayList<H>();
// First get all registered components of the passed class
log.debug("Getting handlers of type " + handlerType + (type == null ? "" : " for class " + type.getName()));
for (H handler : Context.getRegisteredComponents(handlerType)) {
Handler handlerAnnotation = handler.getClass().getAnnotation(Handler.class);
// Only consider those that have been annotated as Handlers
if (handlerAnnotation != null) {
// If no type is passed in return all handlers
if (type == null) {
log.debug("Found handler " + handler.getClass());
handlers.add(handler);
}
// Otherwise, return all handlers that support the passed type
else {
for (int i = 0; i < handlerAnnotation.supports().length; i++) {
Class<?> clazz = handlerAnnotation.supports()[i];
if (clazz.isAssignableFrom(type)) {
log.debug("Found handler: " + handler.getClass());
handlers.add(handler);
}
}
}
}
}
// Return the list of handlers based on the order specified in the Handler annotation
Collections.sort(handlers, new Comparator<H>() {
@Override
public int compare(H o1, H o2) {
return getOrderOfHandler(o1.getClass()).compareTo(getOrderOfHandler(o2.getClass()));
}
});
Map<Key, List<?>> newCachedHandlers = new WeakHashMap<Key, List<?>>(cachedHandlers);
newCachedHandlers.put(new Key(handlerType, type), handlers);
cachedHandlers = newCachedHandlers;
return handlers;
}
/**
* Retrieves the preferred Handler for a given handlerType and type. A <em>preferred</em>
* handler is the Handler that has the lowest defined <em>order</em> attribute in it's
* annotation. If multiple Handlers are found for the passed parameters at the lowest specified
* order, then an APIException is thrown.
*
* @param handlerType the class that is an annotated {@link Handler} to retrieve
* @param type the class that the annotated {@link Handler} must support
* @return the class of the passed handlerType with the lowest configured order
* @should return the preferred handler for the passed handlerType and type
* @should throw a APIException if no handler is found
* @should throw a APIException if multiple preferred handlers are found
* @should should return patient validator for patient
* @should should return person validator for person
*/
public static <H, T> H getPreferredHandler(Class<H> handlerType, Class<T> type) {
if (handlerType == null || type == null) {
throw new IllegalArgumentException("You must specify both a handlerType and a type");
}
List<H> handlers = getHandlersForType(handlerType, type);
if (handlers == null || handlers.isEmpty()) {
throw new APIException("handler.type.not.found", new Object[] { handlerType, type });
}
if (handlers.size() > 1) {
int order1 = getOrderOfHandler(handlers.get(0).getClass());
int order2 = getOrderOfHandler(handlers.get(1).getClass());
if (order1 == order2) {
throw new APIException("handler.type.multiple", new Object[] { handlerType, type });
}
}
return handlers.get(0);
}
/**
* Utility method to return the order attribute of the {@link Handler} annotation on the passed
* class. If the passed class does not have a {@link Handler} annotation, a RuntimeException is
* thrown
*
* @param handlerClass
* @return the order attribute value
*/
public static Integer getOrderOfHandler(Class<?> handlerClass) {
Handler annotation = handlerClass.getAnnotation(Handler.class);
if (annotation == null) {
throw new APIException("class.not.annotated.as.handler", new Object[] { handlerClass });
}
return annotation.order();
}
@Override
public void onApplicationEvent(ContextRefreshedEvent event) {
clearCachedHandlers();
}
}