Java tutorial
/* * 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.jdbi.v3.guava; import com.google.common.base.Optional; import com.google.common.collect.ArrayListMultimap; import com.google.common.collect.BiMap; import com.google.common.collect.HashBiMap; import com.google.common.collect.HashMultimap; import com.google.common.collect.ImmutableList; import com.google.common.collect.ImmutableListMultimap; import com.google.common.collect.ImmutableMap; import com.google.common.collect.ImmutableMultimap; import com.google.common.collect.ImmutableSet; import com.google.common.collect.ImmutableSetMultimap; import com.google.common.collect.ImmutableSortedSet; import com.google.common.collect.LinkedListMultimap; import com.google.common.collect.ListMultimap; import com.google.common.collect.Multimap; import com.google.common.collect.SetMultimap; import com.google.common.collect.TreeMultimap; import org.jdbi.v3.core.collector.CollectorFactory; import java.lang.reflect.ParameterizedType; import java.lang.reflect.Type; import java.lang.reflect.TypeVariable; import java.util.Comparator; import java.util.Map; import java.util.function.Supplier; import java.util.stream.Collector; import static org.jdbi.v3.core.collector.BuiltInCollectorFactory.toMap; import static org.jdbi.v3.core.generic.GenericTypes.findGenericParameter; import static org.jdbi.v3.core.generic.GenericTypes.getErasedType; import static org.jdbi.v3.core.generic.GenericTypes.resolveMapEntryType; import static org.jdbi.v3.core.generic.GenericTypes.resolveType; /** * Provides Collectors for Guava collection types. * <p>Supported container types:</p> * <ul> * <li>com.google.common.base.Optional<T> (throws an exception if more than one row in result)</li> * <li>com.google.common.collect.ImmutableList<T></li> * <li>com.google.common.collect.ImmutableSet<T></li> * <li>com.google.common.collect.ImmutableSortedSet<T extends Comparable></li> * </ul> * <p>Supported Maps and Multimaps types - for rows mapped to Map.Entry<K, V>:</p> * <ul> * <li>com.google.common.collect.BiMap<K, V></li> * <li>com.google.common.collect.ImmutableMap<K, V></li> * <li>com.google.common.collect.Multimap<K, V></li> * <li>com.google.common.collect.ListMultimap<K, V></li> * <li>com.google.common.collect.ArrayListMultimap<K, V></li> * <li>com.google.common.collect.LinkedListMultimap<K, V></li> * <li>com.google.common.collect.SetMultimap<K, V></li> * <li>com.google.common.collect.HashMultimap<K, V></li> * <li>com.google.common.collect.TreeMultimap<K, V></li> * <li>com.google.common.collect.ImmutableMultimap<K, V></li> * <li>com.google.common.collect.ImmutableListMultimap<K, V></li> * <li>com.google.common.collect.ImmutableSetMultimap<K, V></li> * </ul> */ public class GuavaCollectors { /** * @return a {@code CollectorFactory} which knows how to create all supported Guava types */ public static CollectorFactory factory() { return new Factory(); } private static class Factory implements CollectorFactory { private final TypeVariable<Class<Multimap>> multimapKey; private final TypeVariable<Class<Multimap>> multimapValue; public Factory() { TypeVariable<Class<Multimap>>[] multimapParams = Multimap.class.getTypeParameters(); multimapKey = multimapParams[0]; multimapValue = multimapParams[1]; } private final Map<Class<?>, Collector<?, ?, ?>> collectors = ImmutableMap .<Class<?>, Collector<?, ?, ?>>builder().put(ImmutableList.class, ImmutableList.toImmutableList()) .put(ImmutableSet.class, ImmutableSet.toImmutableSet()) .put(ImmutableSortedSet.class, ImmutableSortedSet.toImmutableSortedSet(Comparator.naturalOrder())) .put(Optional.class, toOptional()).put(ImmutableMap.class, toImmutableMap()) .put(BiMap.class, toHashBiMap()).put(ImmutableMultimap.class, toImmutableListMultimap()) .put(ImmutableListMultimap.class, toImmutableListMultimap()) .put(ImmutableSetMultimap.class, toImmutableSetMultimap()) .put(Multimap.class, toImmutableListMultimap()).put(ListMultimap.class, toImmutableListMultimap()) .put(ArrayListMultimap.class, toArrayListMultimap()) .put(LinkedListMultimap.class, toLinkedListMultimap()) .put(SetMultimap.class, toImmutableSetMultimap()).put(HashMultimap.class, toHashMultimap()) .put(TreeMultimap.class, toTreeMultimap()).build(); @Override public boolean accepts(Type containerType) { Class<?> erasedType = getErasedType(containerType); return collectors.containsKey(erasedType) && containerType instanceof ParameterizedType; } @Override public java.util.Optional<Type> elementType(Type containerType) { Class<?> erasedType = getErasedType(containerType); if (Multimap.class.isAssignableFrom(erasedType)) { Type keyType = resolveType(multimapKey, containerType); Type valueType = resolveType(multimapValue, containerType); return java.util.Optional.of(resolveMapEntryType(keyType, valueType)); } else if (Map.class.isAssignableFrom(erasedType)) { return java.util.Optional.of(resolveMapEntryType(containerType)); } return findGenericParameter(containerType, erasedType); } @Override public Collector<?, ?, ?> build(Type containerType) { return collectors.get(getErasedType(containerType)); } } /** * Returns a {@code Collector} that accumulates 0 or 1 input elements into Guava's {@code Optional<T>}. * The returned collector will throw {@code IllegalStateException} whenever 2 or more elements * are present in a stream. * * @param <T> the collected type * @return a {@code Collector} which collects 0 or 1 input elements into a Guava {@code Optional<T>}. */ public static <T> Collector<T, ?, Optional<T>> toOptional() { return Collector.<T, GuavaOptionalBuilder<T>, Optional<T>>of(GuavaOptionalBuilder::new, GuavaOptionalBuilder::set, (left, right) -> left.build().isPresent() ? left : right, GuavaOptionalBuilder::build); } private static class GuavaOptionalBuilder<T> { private Optional<T> optional = Optional.absent(); public void set(T value) { if (optional.isPresent()) { throw new IllegalStateException( String.format("Multiple values for Optional type: ['%s','%s',...]", optional.get(), value)); } optional = Optional.of(value); } public Optional<T> build() { return optional; } } /** * Returns a {@code Collector} that accumulates {@code Map.Entry<K, V>} input elements into an * {@code ImmutableMap<K, V>}. * * @param <K> the type of map keys * @param <V> the type of map values * @return a {@code Collector} which collects map entry elements into an {@code ImmutableMap}, * in encounter order. */ public static <K, V> Collector<Map.Entry<K, V>, ?, ImmutableMap<K, V>> toImmutableMap() { return ImmutableMap.toImmutableMap(Map.Entry::getKey, Map.Entry::getValue); } /** * Returns a {@code Collector} that accumulates {@code Map.Entry<K, V>} input elements into a * {@code HashBiMap<K, V>}. The returned collector will throw {@code IllegalStateException} * whenever a set of input elements contains multiple entries with the same key. * * @param <K> the type of map keys * @param <V> the type of map values * @return a {@code Collector} which collects map entry elements into a {@code HashBiMap}, * in encounter order. */ public static <K, V> Collector<Map.Entry<K, V>, ?, BiMap<K, V>> toHashBiMap() { return toMap(HashBiMap::create); } /** * Returns a {@code Collector} that accumulates {@code Map.Entry<K, V>} input elements into an * {@code ImmutableListMultimap<K, V>}. * * @param <K> the type of map keys * @param <V> the type of map values * @return a {@code Collector} which collects map entry elements into an {@code ImmutableListMultimap}, * in encounter order. */ public static <K, V> Collector<Map.Entry<K, V>, ?, ImmutableListMultimap<K, V>> toImmutableListMultimap() { return Collector.of(ImmutableListMultimap::<K, V>builder, ImmutableListMultimap.Builder::put, GuavaCollectors::combine, ImmutableListMultimap.Builder::build); } /** * Returns a {@code Collector} that accumulates {@code Map.Entry<K, V>} input elements into an * {@code ImmutableSetMultimap<K, V>}. * * @param <K> the type of map keys * @param <V> the type of map values * @return a {@code Collector} which collects map entry elements into an {@code ImmutableSetMultimap}, * in encounter order. */ public static <K, V> Collector<Map.Entry<K, V>, ?, ImmutableSetMultimap<K, V>> toImmutableSetMultimap() { return Collector.of(ImmutableSetMultimap::<K, V>builder, ImmutableSetMultimap.Builder::put, GuavaCollectors::combine, ImmutableSetMultimap.Builder::build); } /** * Returns a {@code Collector} that accumulates {@code Map.Entry<K, V>} input elements into an * {@code ArrayListMultimap<K, V>}. * * @param <K> the type of map keys * @param <V> the type of map values * @return a {@code Collector} which collects map entry elements into an {@code ArrayListMultimap}, * in encounter order. */ public static <K, V> Collector<Map.Entry<K, V>, ?, ArrayListMultimap<K, V>> toArrayListMultimap() { return toMultimap(ArrayListMultimap::create); } /** * Returns a {@code Collector} that accumulates {@code Map.Entry<K, V>} input elements into a * {@code LinkedListMultimap<K, V>}. * * @param <K> the type of map keys * @param <V> the type of map values * @return a {@code Collector} which collects map entry elements into a {@code LinkedListMultimap}, * in encounter order. */ public static <K, V> Collector<Map.Entry<K, V>, ?, LinkedListMultimap<K, V>> toLinkedListMultimap() { return toMultimap(LinkedListMultimap::create); } /** * Returns a {@code Collector} that accumulates {@code Map.Entry<K, V>} input elements into a * {@code HashMultimap<K, V>}. * * @param <K> the type of map keys * @param <V> the type of map values * @return a {@code Collector} which collects map entry elements into a {@code ArrayListMultimap}, * in encounter order. */ public static <K, V> Collector<Map.Entry<K, V>, ?, HashMultimap<K, V>> toHashMultimap() { return toMultimap(HashMultimap::create); } /** * Returns a {@code Collector} that accumulates {@code Map.Entry<K, V>} input elements into a * {@code TreeMultimap<K, V>}. * * @param <K> the type of map keys * @param <V> the type of map values * @return a {@code Collector} which collects map entry elements into a {@code TreeMultimap}, * in encounter order. */ public static <K extends Comparable, V extends Comparable> Collector<Map.Entry<K, V>, ?, TreeMultimap<K, V>> toTreeMultimap() { return toMultimap(TreeMultimap::create); } /** * Returns a {@code Collector} that accumulates {@code Map.Entry<K, V>} input elements into a * {@code Multimap<K, V>} of the supplied type. * * @param <K> the type of map keys * @param <V> the type of map values * @param <M> a supplier of your multimap type * @param multimapFactory a {@code Supplier} which return a new, empty {@code Multimap} of the appropriate type. * @return a {@code Collector} which collects map entry elements into a {@code Multiamp}, in encounter order. */ public static <K, V, M extends Multimap<K, V>> Collector<Map.Entry<K, V>, ?, M> toMultimap( Supplier<M> multimapFactory) { return Collector.of(multimapFactory, GuavaCollectors::putEntry, GuavaCollectors::combine); } private static <K, V, M extends Multimap<K, V>> void putEntry(M map, Map.Entry<K, V> entry) { map.put(entry.getKey(), entry.getValue()); } private static <K, V, M extends Multimap<K, V>> M combine(M a, M b) { a.putAll(b); return a; } private static <K, V, MB extends ImmutableMultimap.Builder<K, V>> MB combine(MB a, MB b) { a.putAll(b.build()); return a; } }