/*****************************************************************
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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.apache.cayenne.util;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import org.apache.cayenne.BaseContext;
import org.apache.cayenne.ObjectContext;
import org.apache.cayenne.ObjectId;
import org.apache.cayenne.PersistenceState;
import org.apache.cayenne.Persistent;
import org.apache.cayenne.QueryResponse;
import org.apache.cayenne.cache.QueryCache;
import org.apache.cayenne.cache.QueryCacheEntryFactory;
import org.apache.cayenne.query.ObjectIdQuery;
import org.apache.cayenne.query.Query;
import org.apache.cayenne.query.QueryCacheStrategy;
import org.apache.cayenne.query.QueryMetadata;
import org.apache.cayenne.query.RelationshipQuery;
import org.apache.cayenne.reflect.ArcProperty;
import org.apache.cayenne.reflect.ClassDescriptor;
/**
* A helper class that implements
* {@link org.apache.cayenne.DataChannel#onQuery(ObjectContext, Query)} logic on behalf of
* an ObjectContext.
* <p>
* <i>Intended for internal use only.</i>
* </p>
*
* @since 1.2
*/
public abstract class ObjectContextQueryAction {
protected static final boolean DONE = true;
protected ObjectContext targetContext;
protected ObjectContext actingContext;
protected Query query;
protected QueryMetadata metadata;
protected boolean queryOriginator;
protected transient QueryResponse response;
public ObjectContextQueryAction(ObjectContext actingContext,
ObjectContext targetContext, Query query) {
this.actingContext = actingContext;
this.query = query;
// this means that a caller must pass self as both acting context and target
// context to indicate that a query originated here... null (ROP) or differing
// context indicates that the query was originated elsewhere, which has
// consequences in LOCAL_CACHE handling
this.queryOriginator = targetContext != null && targetContext == actingContext;
// no special target context and same target context as acting context mean the
// same thing. "normalize" the internal state to avoid confusion
this.targetContext = targetContext != actingContext ? targetContext : null;
this.metadata = query.getMetaData(actingContext.getEntityResolver());
}
/**
* Worker method that performs internal query.
*/
public QueryResponse execute() {
if (interceptOIDQuery() != DONE) {
if (interceptRelationshipQuery() != DONE) {
if (interceptRefreshQuery() != DONE) {
if (interceptLocalCache() != DONE) {
executePostCache();
}
}
}
}
interceptObjectConversion();
return response;
}
private void executePostCache() {
if (interceptInternalQuery() != DONE) {
if (interceptPaginatedQuery() != DONE) {
runQuery();
}
}
}
/**
* Transfers fetched objects into the target context if it is different from "acting"
* context. Note that when this method is invoked, result objects are already
* registered with acting context by the parent channel.
*/
protected void interceptObjectConversion() {
if (targetContext != null && !metadata.isFetchingDataRows()) {
// rewrite response to contain objects from the query context
GenericResponse childResponse = new GenericResponse();
for (response.reset(); response.next();) {
if (response.isList()) {
List objects = response.currentList();
if (objects.isEmpty()) {
childResponse.addResultList(objects);
}
else {
// TODO: Andrus 1/31/2006 - IncrementalFaultList is not properly
// transferred between contexts....
List childObjects = new ArrayList(objects.size());
Iterator it = objects.iterator();
while (it.hasNext()) {
Persistent object = (Persistent) it.next();
childObjects.add(targetContext.localObject(object
.getObjectId(), object));
}
childResponse.addResultList(childObjects);
}
}
else {
childResponse.addBatchUpdateCount(response.currentUpdateCount());
}
}
response = childResponse;
}
}
protected boolean interceptInternalQuery() {
return !DONE;
}
protected boolean interceptOIDQuery() {
if (query instanceof ObjectIdQuery) {
ObjectIdQuery oidQuery = (ObjectIdQuery) query;
if (!oidQuery.isFetchMandatory() && !oidQuery.isFetchingDataRows()) {
Object object = actingContext.getGraphManager().getNode(
oidQuery.getObjectId());
if (object != null) {
// do not return hollow objects
if (((Persistent) object).getPersistenceState() == PersistenceState.HOLLOW) {
return !DONE;
}
this.response = new ListResponse(object);
return DONE;
}
}
}
return !DONE;
}
protected boolean interceptRelationshipQuery() {
if (query instanceof RelationshipQuery) {
RelationshipQuery relationshipQuery = (RelationshipQuery) query;
if (!relationshipQuery.isRefreshing()) {
// don't intercept to-many relationships if fetch is done to the same
// context as the root context of this action - this will result in an
// infinite loop.
if (targetContext == null
&& relationshipQuery.getRelationship(
actingContext.getEntityResolver()).isToMany()) {
return !DONE;
}
ObjectId id = relationshipQuery.getObjectId();
Object object = actingContext.getGraphManager().getNode(id);
if (object != null) {
ClassDescriptor descriptor = actingContext
.getEntityResolver()
.getClassDescriptor(id.getEntityName());
if (!descriptor.isFault(object)) {
ArcProperty property = (ArcProperty) descriptor
.getProperty(relationshipQuery.getRelationshipName());
if (!property.isFault(object)) {
Object related = property.readPropertyDirectly(object);
List result;
// null to-one
if (related == null) {
result = new ArrayList(1);
}
// to-many
else if (related instanceof List) {
result = (List) related;
}
// non-null to-one
else {
result = new ArrayList(1);
result.add(related);
}
this.response = new ListResponse(result);
return DONE;
}
/**
* Workaround for CAY-1183. If a Relationship query is being sent from
* child context, we assure that local object is not NEW and relationship - unresolved
* (this way exception will occur). This helps when faulting objects that
* were committed to parent context (this), but not to database.
*
* Checking type of context's channel is the only way to ensure that we are
* on the top level of context hierarchy (there might be more than one-level-deep
* nested contexts).
*/
if (((Persistent) object).getPersistenceState() == PersistenceState.NEW
&& !(actingContext.getChannel() instanceof BaseContext)) {
this.response = new ListResponse();
return DONE;
}
}
}
}
}
return !DONE;
}
/**
* @since 3.0
*/
protected abstract boolean interceptPaginatedQuery();
/**
* @since 3.0
*/
protected abstract boolean interceptRefreshQuery();
/**
* @since 3.0
*/
protected boolean interceptLocalCache() {
if (metadata.getCacheKey() == null) {
return !DONE;
}
// ignore local cache unless this context originated the query...
if (!queryOriginator) {
return !DONE;
}
boolean cache = QueryCacheStrategy.LOCAL_CACHE == metadata.getCacheStrategy();
boolean cacheOrCacheRefresh = cache
|| QueryCacheStrategy.LOCAL_CACHE_REFRESH == metadata.getCacheStrategy();
if (!cacheOrCacheRefresh) {
return !DONE;
}
QueryCache queryCache = getQueryCache();
QueryCacheEntryFactory factory = getCacheObjectFactory();
if (cache) {
List cachedResults = queryCache.get(metadata, factory);
// response may already be initialized by the factory above ... it is null if
// there was a preexisting cache entry
if (response == null) {
response = new ListResponse(cachedResults);
}
}
else {
// on cache-refresh request, fetch without blocking and fill the cache
queryCache.put(metadata, (List) factory.createObject());
}
return DONE;
}
/**
* @since 3.0
*/
protected QueryCache getQueryCache() {
return ((BaseContext) actingContext).getQueryCache();
}
/**
* @since 3.0
*/
protected QueryCacheEntryFactory getCacheObjectFactory() {
return new QueryCacheEntryFactory() {
public Object createObject() {
executePostCache();
return response.firstList();
}
};
}
/**
* Fetches data from the channel.
*/
protected void runQuery() {
this.response = actingContext.getChannel().onQuery(actingContext, query);
}
}