org.springframework.core.convert.support.CollectionToStringConverter Maven / Gradle / Ivy
/*
* Copyright 2002-2016 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.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;
/**
* Converts a Collection to a comma-delimited String.
*
* @author Keith Donald
* @since 3.0
*/
final class CollectionToStringConverter implements ConditionalGenericConverter {
private static final String DELIMITER = ",";
private final ConversionService conversionService;
public CollectionToStringConverter(ConversionService conversionService) {
this.conversionService = conversionService;
}
@Override
public Set getConvertibleTypes() {
return Collections.singleton(new ConvertiblePair(Collection.class, String.class));
}
@Override
public boolean matches(TypeDescriptor sourceType, TypeDescriptor targetType) {
return ConversionUtils.canConvertElements(
sourceType.getElementTypeDescriptor(), targetType, this.conversionService);
}
@Override
@Nullable
public Object convert(@Nullable Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
if (source == null) {
return null;
}
Collection sourceCollection = (Collection) source;
if (sourceCollection.isEmpty()) {
return "";
}
StringBuilder sb = new StringBuilder();
int i = 0;
for (Object sourceElement : sourceCollection) {
if (i > 0) {
sb.append(DELIMITER);
}
Object targetElement = this.conversionService.convert(
sourceElement, sourceType.elementTypeDescriptor(sourceElement), targetType);
sb.append(targetElement);
i++;
}
return sb.toString();
}
}