org.springframework.core.CollectionFactory Maven / Gradle / Ivy
/*
* Copyright 2002-2007 the original author or authors.
*
* 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.springframework.core;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.IdentityHashMap;
import java.util.LinkedHashMap;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.SortedMap;
import java.util.SortedSet;
import java.util.TreeMap;
import java.util.TreeSet;
import org.apache.commons.collections.map.CaseInsensitiveMap;
import org.apache.commons.collections.map.IdentityMap;
import org.apache.commons.collections.map.LinkedMap;
import org.apache.commons.collections.map.ListOrderedMap;
import org.apache.commons.collections.set.ListOrderedSet;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.util.ClassUtils;
/**
* Factory for collections, being aware of JDK 1.4+ extended collections
* and Commons Collection 3.x's corresponding versions for older JDKs.
* Mainly for internal use within the framework.
*
* The goal of this class is to avoid runtime dependencies on JDK 1.4+
* or Commons Collections 3.x, simply using the best collection implementation
* that is available. Prefers JDK 1.4+ collection implementations to Commons
* Collections 3.x versions, falling back to JDK 1.3 collections as worst case.
*
* @author Juergen Hoeller
* @since 1.1.1
* @see #createLinkedSetIfPossible
* @see #createLinkedMapIfPossible
* @see #createLinkedCaseInsensitiveMapIfPossible
* @see #createIdentityMapIfPossible
*/
public abstract class CollectionFactory {
private static final Log logger = LogFactory.getLog(CollectionFactory.class);
/** Whether the Commons Collections 3.x library is present on the classpath */
private static final boolean commonsCollections3Available =
ClassUtils.isPresent(
"org.apache.commons.collections.map.LinkedMap", CollectionFactory.class.getClassLoader());
/**
* Create a linked set if possible: that is, if running on JDK >= 1.4
* or if Commons Collections 3.x is available. Prefers a JDK 1.4+
* LinkedHashSet to a Commons Collections 3.x ListOrderedSet.
* @param initialCapacity the initial capacity of the set
* @return the new set instance
* @see java.util.LinkedHashSet
* @see org.apache.commons.collections.set.ListOrderedSet
*/
public static Set createLinkedSetIfPossible(int initialCapacity) {
if (JdkVersion.isAtLeastJava14()) {
logger.trace("Creating [java.util.LinkedHashSet]");
return Jdk14CollectionFactory.createLinkedHashSet(initialCapacity);
}
else if (commonsCollections3Available) {
logger.trace("Creating [org.apache.commons.collections.set.ListOrderedSet]");
return CommonsCollectionFactory.createListOrderedSet(initialCapacity);
}
else {
logger.debug("Falling back to plain [java.util.HashSet] for linked set");
return new HashSet(initialCapacity);
}
}
/**
* Create a linked map if possible: that is, if running on JDK >= 1.4
* or if Commons Collections 3.x is available. Prefers a JDK 1.4+
* LinkedHashMap to a Commons Collections 3.x LinkedMap.
* @param initialCapacity the initial capacity of the map
* @return the new map instance
* @see java.util.LinkedHashMap
* @see org.apache.commons.collections.map.LinkedMap
*/
public static Map createLinkedMapIfPossible(int initialCapacity) {
if (JdkVersion.isAtLeastJava14()) {
logger.trace("Creating [java.util.LinkedHashMap]");
return Jdk14CollectionFactory.createLinkedHashMap(initialCapacity);
}
else if (commonsCollections3Available) {
logger.trace("Creating [org.apache.commons.collections.map.LinkedMap]");
return CommonsCollectionFactory.createLinkedMap(initialCapacity);
}
else {
logger.debug("Falling back to plain[java.util.HashMap] for linked map");
return new HashMap(initialCapacity);
}
}
/**
* Create a linked case-insensitive map if possible: if Commons Collections
* 3.x is available, a CaseInsensitiveMap with ListOrderedMap decorator will
* be created. Else, a JDK 1.4+ LinkedHashMap or plain HashMap will be used.
* @param initialCapacity the initial capacity of the map
* @return the new map instance
* @see org.apache.commons.collections.map.CaseInsensitiveMap
* @see org.apache.commons.collections.map.ListOrderedMap
*/
public static Map createLinkedCaseInsensitiveMapIfPossible(int initialCapacity) {
if (commonsCollections3Available) {
logger.trace("Creating [org.apache.commons.collections.map.ListOrderedMap/CaseInsensitiveMap]");
return CommonsCollectionFactory.createListOrderedCaseInsensitiveMap(initialCapacity);
}
else if (JdkVersion.isAtLeastJava14()) {
logger.debug("Falling back to [java.util.LinkedHashMap] for linked case-insensitive map");
return Jdk14CollectionFactory.createLinkedHashMap(initialCapacity);
}
else {
logger.debug("Falling back to plain [java.util.HashMap] for linked case-insensitive map");
return new HashMap(initialCapacity);
}
}
/**
* Create an identity map if possible: that is, if running on JDK >= 1.4
* or if Commons Collections 3.x is available. Prefers a JDK 1.4+
* IdentityHashMap to a Commons Collections 3.x IdentityMap.
* @param initialCapacity the initial capacity of the map
* @return the new map instance
* @see java.util.IdentityHashMap
* @see org.apache.commons.collections.map.IdentityMap
*/
public static Map createIdentityMapIfPossible(int initialCapacity) {
if (JdkVersion.isAtLeastJava14()) {
logger.trace("Creating [java.util.IdentityHashMap]");
return Jdk14CollectionFactory.createIdentityHashMap(initialCapacity);
}
else if (commonsCollections3Available) {
logger.trace("Creating [org.apache.commons.collections.map.IdentityMap]");
return CommonsCollectionFactory.createIdentityMap(initialCapacity);
}
else {
logger.debug("Falling back to plain [java.util.HashMap] for identity map");
return new HashMap(initialCapacity);
}
}
/**
* Create the most approximate collection for the given collection.
*
Creates an ArrayList, TreeSet or linked Set for a List, SortedSet
* or Set, respectively.
* @param collection the original collection object
* @param initialCapacity the initial capacity
* @return the new collection instance
* @see java.util.ArrayList
* @see java.util.TreeSet
* @see #createLinkedSetIfPossible
*/
public static Collection createApproximateCollection(Object collection, int initialCapacity) {
if (collection instanceof List) {
return new ArrayList(initialCapacity);
}
else if (collection instanceof SortedSet) {
return new TreeSet(((SortedSet) collection).comparator());
}
else {
return createLinkedSetIfPossible(initialCapacity);
}
}
/**
* Create the most approximate map for the given map.
*
Creates a TreeMap or linked Map for a SortedMap or Map, respectively.
* @param map the original map object
* @param initialCapacity the initial capacity
* @return the new collection instance
* @see java.util.TreeMap
* @see #createLinkedMapIfPossible
*/
public static Map createApproximateMap(Object map, int initialCapacity) {
if (map instanceof SortedMap) {
return new TreeMap(((SortedMap) map).comparator());
}
else {
return createLinkedMapIfPossible(initialCapacity);
}
}
/**
* Actual creation of JDK 1.4+ Collections.
* In separate inner class to avoid runtime dependency on JDK 1.4+.
*/
private static abstract class Jdk14CollectionFactory {
private static Set createLinkedHashSet(int initialCapacity) {
return new LinkedHashSet(initialCapacity);
}
private static Map createLinkedHashMap(int initialCapacity) {
return new LinkedHashMap(initialCapacity);
}
private static Map createIdentityHashMap(int initialCapacity) {
return new IdentityHashMap(initialCapacity);
}
}
/**
* Actual creation of Commons Collections.
* In separate inner class to avoid runtime dependency on Commons Collections 3.x.
*/
private static abstract class CommonsCollectionFactory {
private static Set createListOrderedSet(int initialCapacity) {
return ListOrderedSet.decorate(new HashSet(initialCapacity));
}
private static Map createLinkedMap(int initialCapacity) {
// Commons Collections does not support initial capacity of 0.
return new LinkedMap(initialCapacity == 0 ? 1 : initialCapacity);
}
private static Map createListOrderedCaseInsensitiveMap(int initialCapacity) {
// Commons Collections does not support initial capacity of 0.
return ListOrderedMap.decorate(new CaseInsensitiveMap(initialCapacity == 0 ? 1 : initialCapacity));
}
private static Map createIdentityMap(int initialCapacity) {
// Commons Collections does not support initial capacity of 0.
return new IdentityMap(initialCapacity == 0 ? 1 : initialCapacity);
}
}
}