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/*
* Copyright 2010-2014 Ning, Inc.
*
* Ning 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.killbill.billing.util.entity.dao;
import java.util.LinkedList;
import java.util.List;
import java.util.Objects;
import java.util.function.Function;
import org.killbill.billing.BillingExceptionBase;
import org.killbill.commons.utils.collect.Iterables;
import org.killbill.commons.utils.collect.Iterators;
import org.killbill.billing.util.customfield.ShouldntHappenException;
import org.killbill.billing.util.entity.DefaultPagination;
import org.killbill.billing.util.entity.Entity;
import org.killbill.billing.util.entity.Pagination;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public class DefaultPaginationHelper {
private static final Logger log = LoggerFactory.getLogger(DefaultPaginationHelper.class);
public abstract static class EntityPaginationBuilder {
public abstract Pagination build(final Long offset, final Long limit, final String pluginName) throws T;
}
public static Pagination getEntityPaginationFromPlugins(final boolean maxStatsCrossPlugins, final Iterable plugins, final Long offset, final Long limit, final EntityPaginationBuilder entityPaginationBuilder) {
// Note that we cannot easily do streaming here, since we would have to rely on the statistics
// returned by the Pagination objects from the plugins and we probably don't want to do that (if
// one plugin gets it wrong, it may starve the others).
final List allResults = new LinkedList();
Long totalNbRecords = 0L;
Long maxNbRecords = 0L;
// Search in all plugins (we treat the full set of results as a union with respect to offset/limit)
boolean firstSearch = true;
for (final String pluginName : plugins) {
try {
final Pagination pages;
if (allResults.size() >= limit) {
// We have enough results, we just keep going (limit 1) to get the stats
pages = entityPaginationBuilder.build(firstSearch ? offset : 0L, 1L, pluginName);
closeDatabaseConnection(pages);
} else {
pages = entityPaginationBuilder.build(firstSearch ? offset : 0L, limit - allResults.size(), pluginName);
pages.forEach(allResults::add);
}
// Make sure not to start at 0 for subsequent plugins if previous ones didn't yield any result
firstSearch = allResults.isEmpty();
totalNbRecords += pages.getTotalNbRecords();
if (!maxStatsCrossPlugins) {
maxNbRecords += pages.getMaxNbRecords();
} else {
// getPayments and getPaymentMethods return MaxNbRecords across all plugins -- make sure we don't double count
maxNbRecords = Math.max(maxNbRecords, pages.getMaxNbRecords());
}
} catch (final BillingExceptionBase e) {
log.warn("Error while searching plugin='{}'", pluginName, e);
// Non-fatal, continue to search other plugins
}
}
return new DefaultPagination(offset, limit, totalNbRecords, maxNbRecords, allResults.iterator());
}
public abstract static class SourcePaginationBuilder {
public abstract Pagination build() throws T;
}
public static Pagination getEntityPagination(final Long limit,
final SourcePaginationBuilder sourcePaginationBuilder,
final Function function) throws T {
final Pagination modelsDao = sourcePaginationBuilder.build();
return new DefaultPagination(modelsDao, limit, Iterables.toStream(modelsDao).map(function).filter(Objects::nonNull).iterator());
}
public static Pagination getEntityPaginationNoException(final Long limit,
final SourcePaginationBuilder sourcePaginationBuilder,
final Function function) {
try {
return getEntityPagination(limit, sourcePaginationBuilder, function);
} catch (final BillingExceptionBase e) {
throw new ShouldntHappenException("No exception expected" + e);
}
}
/**
* Iterate all element to avoid memory leak.
*/
private static void closeDatabaseConnection(final Iterable page) {
Iterators.toUnmodifiableList(page.iterator());
}
}
