org.springframework.core.convert.support.CollectionToCollectionConverter Maven / Gradle / Ivy
/*
* Copyright 2002-2014 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
*
* https://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.convert.support;
import java.util.Collection;
import java.util.Collections;
import java.util.Set;
import org.springframework.core.CollectionFactory;
import org.springframework.core.convert.ConversionService;
import org.springframework.core.convert.TypeDescriptor;
import org.springframework.core.convert.converter.ConditionalGenericConverter;
import org.springframework.lang.Nullable;
/**
* Converts from a Collection to another Collection.
*
* First, creates a new Collection of the requested targetType with a size equal to the
* size of the source Collection. Then copies each element in the source collection to the
* target collection. Will perform an element conversion from the source collection's
* parameterized type to the target collection's parameterized type if necessary.
*
* @author Keith Donald
* @author Juergen Hoeller
* @since 3.0
*/
final class CollectionToCollectionConverter implements ConditionalGenericConverter {
private final ConversionService conversionService;
public CollectionToCollectionConverter(ConversionService conversionService) {
this.conversionService = conversionService;
}
@Override
public Set getConvertibleTypes() {
return Collections.singleton(new ConvertiblePair(Collection.class, Collection.class));
}
@Override
public boolean matches(TypeDescriptor sourceType, TypeDescriptor targetType) {
return ConversionUtils.canConvertElements(
sourceType.getElementTypeDescriptor(), targetType.getElementTypeDescriptor(), this.conversionService);
}
@Override
@Nullable
public Object convert(@Nullable Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
if (source == null) {
return null;
}
Collection sourceCollection = (Collection) source;
// Shortcut if possible...
boolean copyRequired = !targetType.getType().isInstance(source);
if (!copyRequired && sourceCollection.isEmpty()) {
return source;
}
TypeDescriptor elementDesc = targetType.getElementTypeDescriptor();
if (elementDesc == null && !copyRequired) {
return source;
}
// At this point, we need a collection copy in any case, even if just for finding out about element copies...
Collection