org.springframework.core.convert.support.ObjectToOptionalConverter Maven / Gradle / Ivy
/*
* 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
*
* 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.lang.reflect.Array;
import java.util.Collection;
import java.util.LinkedHashSet;
import java.util.Optional;
import java.util.Set;
import org.springframework.core.convert.ConversionService;
import org.springframework.core.convert.TypeDescriptor;
import org.springframework.core.convert.converter.ConditionalGenericConverter;
import org.springframework.lang.Nullable;
/**
* Convert an Object to {@code java.util.Optional} if necessary using the
* {@code ConversionService} to convert the source Object to the generic type
* of Optional when known.
*
* @author Rossen Stoyanchev
* @author Juergen Hoeller
* @since 4.1
*/
final class ObjectToOptionalConverter implements ConditionalGenericConverter {
private final ConversionService conversionService;
public ObjectToOptionalConverter(ConversionService conversionService) {
this.conversionService = conversionService;
}
@Override
public Set getConvertibleTypes() {
Set convertibleTypes = new LinkedHashSet<>(4);
convertibleTypes.add(new ConvertiblePair(Collection.class, Optional.class));
convertibleTypes.add(new ConvertiblePair(Object[].class, Optional.class));
convertibleTypes.add(new ConvertiblePair(Object.class, Optional.class));
return convertibleTypes;
}
@Override
public boolean matches(TypeDescriptor sourceType, TypeDescriptor targetType) {
if (targetType.getResolvableType().hasGenerics()) {
return this.conversionService.canConvert(sourceType, new GenericTypeDescriptor(targetType));
}
else {
return true;
}
}
@Override
public Object convert(@Nullable Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
if (source == null) {
return Optional.empty();
}
else if (source instanceof Optional) {
return source;
}
else if (targetType.getResolvableType().hasGenerics()) {
Object target = this.conversionService.convert(source, sourceType, new GenericTypeDescriptor(targetType));
if (target == null || (target.getClass().isArray() && Array.getLength(target) == 0) ||
(target instanceof Collection && ((Collection) target).isEmpty())) {
return Optional.empty();
}
return Optional.of(target);
}
else {
return Optional.of(source);
}
}
@SuppressWarnings("serial")
private static class GenericTypeDescriptor extends TypeDescriptor {
public GenericTypeDescriptor(TypeDescriptor typeDescriptor) {
super(typeDescriptor.getResolvableType().getGeneric(), null, typeDescriptor.getAnnotations());
}
}
}