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/*
* Copyright 2002-2017 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.convert.support;
import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import java.util.stream.Collectors;
import java.util.stream.Stream;
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 a {@link Stream} to and from a collection or array, converting the
* element type if necessary.
*
* @author Stephane Nicoll
* @since 4.2
*/
class StreamConverter implements ConditionalGenericConverter {
private static final TypeDescriptor STREAM_TYPE = TypeDescriptor.valueOf(Stream.class);
private static final Set CONVERTIBLE_TYPES = createConvertibleTypes();
private final ConversionService conversionService;
public StreamConverter(ConversionService conversionService) {
this.conversionService = conversionService;
}
@Override
public Set getConvertibleTypes() {
return CONVERTIBLE_TYPES;
}
@Override
public boolean matches(TypeDescriptor sourceType, TypeDescriptor targetType) {
if (sourceType.isAssignableTo(STREAM_TYPE)) {
return matchesFromStream(sourceType.getElementTypeDescriptor(), targetType);
}
if (targetType.isAssignableTo(STREAM_TYPE)) {
return matchesToStream(targetType.getElementTypeDescriptor(), sourceType);
}
return false;
}
/**
* Validate that a {@link Collection} of the elements held within the stream can be
* converted to the specified {@code targetType}.
* @param elementType the type of the stream elements
* @param targetType the type to convert to
*/
public boolean matchesFromStream(@Nullable TypeDescriptor elementType, TypeDescriptor targetType) {
TypeDescriptor collectionOfElement = TypeDescriptor.collection(Collection.class, elementType);
return this.conversionService.canConvert(collectionOfElement, targetType);
}
/**
* Validate that the specified {@code sourceType} can be converted to a {@link Collection} of
* the type of the stream elements.
* @param elementType the type of the stream elements
* @param sourceType the type to convert from
*/
public boolean matchesToStream(@Nullable TypeDescriptor elementType, TypeDescriptor sourceType) {
TypeDescriptor collectionOfElement = TypeDescriptor.collection(Collection.class, elementType);
return this.conversionService.canConvert(sourceType, collectionOfElement);
}
@Override
@Nullable
public Object convert(@Nullable Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
if (sourceType.isAssignableTo(STREAM_TYPE)) {
return convertFromStream((Stream) source, sourceType, targetType);
}
if (targetType.isAssignableTo(STREAM_TYPE)) {
return convertToStream(source, sourceType, targetType);
}
// Should not happen
throw new IllegalStateException("Unexpected source/target types");
}
@Nullable
private Object convertFromStream(@Nullable Stream source, TypeDescriptor streamType, TypeDescriptor targetType) {
List