HierarchicFinderSupport.java
/*
* *********************************************************************************************************************
*
* TheseFoolishThings: Miscellaneous utilities
* http://tidalwave.it/projects/thesefoolishthings
*
* Copyright (C) 2009 - 2023 by Tidalwave s.a.s. (http://tidalwave.it)
*
* *********************************************************************************************************************
*
* 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.
*
* *********************************************************************************************************************
*
* git clone https://bitbucket.org/tidalwave/thesefoolishthings-src
* git clone https://github.com/tidalwave-it/thesefoolishthings-src
*
* *********************************************************************************************************************
*/
package it.tidalwave.util.spi;
import java.lang.reflect.Constructor;
import javax.annotation.Nonnegative;
import javax.annotation.Nonnull;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.CopyOnWriteArrayList;
import it.tidalwave.util.Finder;
import lombok.AccessLevel;
import lombok.AllArgsConstructor;
import lombok.Getter;
import lombok.RequiredArgsConstructor;
import lombok.ToString;
import lombok.extern.slf4j.Slf4j;
import static it.tidalwave.util.CollectionUtils.concat;
/***********************************************************************************************************************
*
* A support class for implementing a {@link Finder}. Subclasses only need to implement the {@link #computeResults()}
* method where <i>raw</i> results are retrieved (with raw we mean that they shouldn't be filtered or sorted, as
* post-processing will be performed by this class) and a clone constructor.
*
* If you don't need to extend the {@link Finder} with extra methods, please use the simplified
* {@link SimpleFinderSupport}.
*
* @author Fabrizio Giudici
* @it.tidalwave.javadoc.draft
*
**********************************************************************************************************************/
@Slf4j @AllArgsConstructor(access = AccessLevel.PRIVATE) @ToString
public class HierarchicFinderSupport<T, F extends Finder<T>> implements Finder<T>
{
private static final long serialVersionUID = 2467809593956684L;
@RequiredArgsConstructor
static class Sorter<U>
{
@Nonnull
private final InMemorySortCriterion<U> sortCriterion;
@Nonnull
private final SortDirection sortDirection;
public void sort (@Nonnull final List<? extends U> results)
{
sortCriterion.sort(results, sortDirection);
}
}
private static final String MESSAGE =
"Since version 2.0, Implementations of Finder must have a clone constructor such as "
+ "MyFinder(MyFinder other, Object override). This means that they can't be implemented by anonymous or inner, "
+ "non static classes. See the javadoc for further information. Could not find constructor: ";
@Nonnull
private final String name;
@Nonnegative
protected final int firstResult;
@Nonnegative
protected final int maxResults;
@Nonnull @Getter(AccessLevel.PROTECTED)
private final List<Object> contexts;
@Nonnull
private final List<Sorter<T>> sorters;
private static final int DEFAULT_MAX_RESULTS = Integer.MAX_VALUE;
/*******************************************************************************************************************
*
* Creates an instance with the given name (that will be used for diagnostics).
*
* @param name the name
*
******************************************************************************************************************/
protected HierarchicFinderSupport (@Nonnull final String name)
{
this.name = name;
this.firstResult = 0;
this.maxResults = DEFAULT_MAX_RESULTS;
this.sorters = new ArrayList<>();
this.contexts = Collections.emptyList();
checkSubClass();
}
/*******************************************************************************************************************
*
* Default constructor.
*
******************************************************************************************************************/
protected HierarchicFinderSupport()
{
this.name = getClass().getName();
this.firstResult = 0;
this.maxResults = DEFAULT_MAX_RESULTS;
this.sorters = new ArrayList<>();
this.contexts = Collections.emptyList();
checkSubClass();
}
/*******************************************************************************************************************
*
* Clone constructor for subclasses.
*
* @param other the other instance to clone
* @param holder the holder object
*
******************************************************************************************************************/
protected HierarchicFinderSupport (@Nonnull final HierarchicFinderSupport<T, F> other, @Nonnull final Object holder)
{
log.trace("HierarchicFinderSupport({}, {})", other, holder);
final var source = getSource(HierarchicFinderSupport.class, other, holder);
this.name = source.name;
this.firstResult = source.firstResult;
this.maxResults = source.maxResults;
this.sorters = source.sorters;
this.contexts = source.contexts; // it's always unmodifiable
}
/*******************************************************************************************************************
*
* This method throws an exception since a {@code Finder} extending this class must be cloned with
* {@link #clonedWith(Object)}.
*
* @see #clonedWith(Object)
* @deprecated
*
******************************************************************************************************************/
@Override @Nonnull
public final HierarchicFinderSupport<T, F> clone()
{
throw new UnsupportedOperationException("\"HierarchicFinderSupport.clone() no more supported");
}
/*******************************************************************************************************************
*
* Create a clone of this object calling the special copy constructor by reflection.
*
* @param override the override object
* @return the clone
*
******************************************************************************************************************/
@Nonnull
protected F clonedWith (@Nonnull final Object override)
{
try
{
final var constructor = getCloneConstructor();
constructor.setAccessible(true);
return (F)constructor.newInstance(this, override);
}
catch (Exception e)
{
throw new RuntimeException(e);
}
}
/*******************************************************************************************************************
*
* Create a clone of this object calling the special clone constructor by reflection.
*
* @param override the override object
* @return the clone
* @deprecated Use {@link #clonedWith(Object)} instead.
*
******************************************************************************************************************/
@Nonnull @Deprecated
protected F clone (@Nonnull final Object override)
{
return clonedWith(override);
}
/*******************************************************************************************************************
*
* {@inheritDoc}
*
******************************************************************************************************************/
@Override @Nonnull
public F from (@Nonnegative final int firstResult)
{
return clonedWith(new HierarchicFinderSupport<T, F>(name, firstResult, maxResults, contexts, sorters));
}
/*******************************************************************************************************************
*
* {@inheritDoc}
*
******************************************************************************************************************/
@Override @Nonnull
public F max (@Nonnegative final int maxResults)
{
return clonedWith(new HierarchicFinderSupport<T, F>(name, firstResult, maxResults, contexts, sorters));
}
/*******************************************************************************************************************
*
* {@inheritDoc}
*
******************************************************************************************************************/
@Override @Nonnull
public F withContext (@Nonnull final Object context)
{
final var contexts = concat(this.contexts, context);
return clonedWith(new HierarchicFinderSupport<T, F>(name, firstResult, maxResults, contexts, sorters));
}
/*******************************************************************************************************************
*
* {@inheritDoc}
*
******************************************************************************************************************/
@Override @Nonnull
public <U> Finder<U> ofType (@Nonnull final Class<U> type)
{
throw new UnsupportedOperationException("Must be eventually implemented by subclasses.");
}
/*******************************************************************************************************************
*
* {@inheritDoc}
*
******************************************************************************************************************/
@Override @Nonnull
public F sort (@Nonnull final SortCriterion criterion, @Nonnull final SortDirection direction)
{
if (criterion instanceof Finder.InMemorySortCriterion)
{
final var sorters = concat(this.sorters, new Sorter<>((InMemorySortCriterion<T>)criterion, direction));
return clonedWith(new HierarchicFinderSupport<T, F>(name, firstResult, maxResults, contexts, sorters));
}
final var template = "%s does not implement %s - you need to subclass Finder and override sort()";
final var message = String.format(template, criterion, InMemorySortCriterion.class);
throw new UnsupportedOperationException(message);
}
/*******************************************************************************************************************
*
* {@inheritDoc}
*
******************************************************************************************************************/
@Override @Nonnull
public final F sort (@Nonnull final SortCriterion criterion)
{
return sort(criterion, SortDirection.ASCENDING);
}
/*******************************************************************************************************************
*
* {@inheritDoc}
*
******************************************************************************************************************/
@Override @Nonnull
public List<T> results()
{
return computeNeededResults();
}
/*******************************************************************************************************************
*
* {@inheritDoc}
*
******************************************************************************************************************/
@Override @Nonnegative
public int count()
{
return computeNeededResults().size();
}
/*******************************************************************************************************************
*
* Subclasses can implement this method where *all* the raw results must be actually retrieved.
*
* @return the unprocessed results
*
******************************************************************************************************************/
// START SNIPPET: computeResults
@Nonnull
protected List<T> computeResults()
// END SNIPPET: computeResults
{
throw new UnsupportedOperationException("You must implement me!");
}
/*******************************************************************************************************************
*
* Subclasses can implement this method where *only the requested* raw results must be retrieved.
*
* @return the unprocessed results
*
******************************************************************************************************************/
// START SNIPPET: computeNeededResults
@Nonnull
protected List<T> computeNeededResults()
// END SNIPPET: computeNeededResults
{
log.trace("computeNeededResults() - {}", this);
var results = computeResults();
// First sort and then extract the sublist
for (final var sorter : sorters)
{
log.trace(">>>> sorting with {}...", sorter);
sorter.sort(results);
}
final var toIndex = (int)Math.min(results.size(), (long)firstResult + (long)maxResults);
if (firstResult > toIndex)
{
return new CopyOnWriteArrayList<>();
}
results = results.subList(firstResult, toIndex);
return results;
}
/*******************************************************************************************************************
*
* A utility method used by the copy constructor (see general documentation). If the override object is strictly
* of the specified type, it is returned; otherwise the other object is returned.
*
* @param <U> the static type of the source
* @param type the dynamic type of the source
* @param other the other finder
* @param override the holder object
* @return the override or other
*
******************************************************************************************************************/
@Nonnull
protected static <U> U getSource (@Nonnull final Class<? extends U> type,
@Nonnull final U other,
@Nonnull final Object override)
{
return override.getClass().equals(type) ? type.cast(override) : other;
}
/*******************************************************************************************************************
*
*
******************************************************************************************************************/
@Nonnull
private Constructor<? extends HierarchicFinderSupport> getCloneConstructor()
throws SecurityException, NoSuchMethodException
{
return getClass().getConstructor(getClass(), Object.class);
}
/*******************************************************************************************************************
*
*
******************************************************************************************************************/
private void checkSubClass()
{
try
{
getCloneConstructor();
}
catch (SecurityException | NoSuchMethodException e)
{
throw new ExceptionInInitializerError(MESSAGE + e.getMessage());
}
}
}