/*
* 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.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Map;
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 a Map to another Map.
First, creates a new Map of the requested targetType with a size equal to the
size of the source Map. Then copies each element in the source map to the target map.
Will perform a conversion from the source maps's parameterized K,V types to the target
map's parameterized types K,V if necessary.
Author: Keith Donald, Juergen Hoeller Since: 3.0
/**
* Converts a Map to another Map.
*
* <p>First, creates a new Map of the requested targetType with a size equal to the
* size of the source Map. Then copies each element in the source map to the target map.
* Will perform a conversion from the source maps's parameterized K,V types to the target
* map's parameterized types K,V if necessary.
*
* @author Keith Donald
* @author Juergen Hoeller
* @since 3.0
*/
final class MapToMapConverter implements ConditionalGenericConverter {
private final ConversionService conversionService;
public MapToMapConverter(ConversionService conversionService) {
this.conversionService = conversionService;
}
@Override
public Set<ConvertiblePair> getConvertibleTypes() {
return Collections.singleton(new ConvertiblePair(Map.class, Map.class));
}
@Override
public boolean matches(TypeDescriptor sourceType, TypeDescriptor targetType) {
return canConvertKey(sourceType, targetType) && canConvertValue(sourceType, targetType);
}
@Override
@SuppressWarnings("unchecked")
@Nullable
public Object convert(@Nullable Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
if (source == null) {
return null;
}
Map<Object, Object> sourceMap = (Map<Object, Object>) source;
// Shortcut if possible...
boolean copyRequired = !targetType.getType().isInstance(source);
if (!copyRequired && sourceMap.isEmpty()) {
return sourceMap;
}
TypeDescriptor keyDesc = targetType.getMapKeyTypeDescriptor();
TypeDescriptor valueDesc = targetType.getMapValueTypeDescriptor();
List<MapEntry> targetEntries = new ArrayList<>(sourceMap.size());
for (Map.Entry<Object, Object> entry : sourceMap.entrySet()) {
Object sourceKey = entry.getKey();
Object sourceValue = entry.getValue();
Object targetKey = convertKey(sourceKey, sourceType, keyDesc);
Object targetValue = convertValue(sourceValue, sourceType, valueDesc);
targetEntries.add(new MapEntry(targetKey, targetValue));
if (sourceKey != targetKey || sourceValue != targetValue) {
copyRequired = true;
}
}
if (!copyRequired) {
return sourceMap;
}
Map<Object, Object> targetMap = CollectionFactory.createMap(targetType.getType(),
(keyDesc != null ? keyDesc.getType() : null), sourceMap.size());
for (MapEntry entry : targetEntries) {
entry.addToMap(targetMap);
}
return targetMap;
}
// internal helpers
private boolean canConvertKey(TypeDescriptor sourceType, TypeDescriptor targetType) {
return ConversionUtils.canConvertElements(sourceType.getMapKeyTypeDescriptor(),
targetType.getMapKeyTypeDescriptor(), this.conversionService);
}
private boolean canConvertValue(TypeDescriptor sourceType, TypeDescriptor targetType) {
return ConversionUtils.canConvertElements(sourceType.getMapValueTypeDescriptor(),
targetType.getMapValueTypeDescriptor(), this.conversionService);
}
@Nullable
private Object convertKey(Object sourceKey, TypeDescriptor sourceType, @Nullable TypeDescriptor targetType) {
if (targetType == null) {
return sourceKey;
}
return this.conversionService.convert(sourceKey, sourceType.getMapKeyTypeDescriptor(sourceKey), targetType);
}
@Nullable
private Object convertValue(Object sourceValue, TypeDescriptor sourceType, @Nullable TypeDescriptor targetType) {
if (targetType == null) {
return sourceValue;
}
return this.conversionService.convert(sourceValue, sourceType.getMapValueTypeDescriptor(sourceValue), targetType);
}
private static class MapEntry {
@Nullable
private final Object key;
@Nullable
private final Object value;
public MapEntry(@Nullable Object key, @Nullable Object value) {
this.key = key;
this.value = value;
}
public void addToMap(Map<Object, Object> map) {
map.put(this.key, this.value);
}
}
}