/*
* Copyright 2002-2009 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.beans.propertyeditors;
import java.beans.PropertyEditorSupport;
import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.Collection;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.SortedSet;
import java.util.TreeSet;
/**
* Property editor for Collections, converting any source Collection
* to a given target Collection type.
*
* <p>By default registered for Set, SortedSet and List,
* to automatically convert any given Collection to one of those
* target types if the type does not match the target property.
*
* @author Juergen Hoeller
* @since 1.1.3
* @see java.util.Collection
* @see java.util.Set
* @see java.util.SortedSet
* @see java.util.List
*/
public class CustomCollectionEditor extends PropertyEditorSupport {
private final Class collectionType;
private final boolean nullAsEmptyCollection;
/**
* Create a new CustomCollectionEditor for the given target type,
* keeping an incoming <code>null</code> as-is.
* @param collectionType the target type, which needs to be a
* sub-interface of Collection or a concrete Collection class
* @see java.util.Collection
* @see java.util.ArrayList
* @see java.util.TreeSet
* @see java.util.LinkedHashSet
*/
public CustomCollectionEditor(Class collectionType) {
this(collectionType, false);
}
/**
* Create a new CustomCollectionEditor for the given target type.
* <p>If the incoming value is of the given type, it will be used as-is.
* If it is a different Collection type or an array, it will be converted
* to a default implementation of the given Collection type.
* If the value is anything else, a target Collection with that single
* value will be created.
* <p>The default Collection implementations are: ArrayList for List,
* TreeSet for SortedSet, and LinkedHashSet for Set.
* @param collectionType the target type, which needs to be a
* sub-interface of Collection or a concrete Collection class
* @param nullAsEmptyCollection whether to convert an incoming <code>null</code>
* value to an empty Collection (of the appropriate type)
* @see java.util.Collection
* @see java.util.ArrayList
* @see java.util.TreeSet
* @see java.util.LinkedHashSet
*/
public CustomCollectionEditor(Class collectionType, boolean nullAsEmptyCollection) {
if (collectionType == null) {
throw new IllegalArgumentException("Collection type is required");
}
if (!Collection.class.isAssignableFrom(collectionType)) {
throw new IllegalArgumentException(
"Collection type [" + collectionType.getName() + "] does not implement [java.util.Collection]");
}
this.collectionType = collectionType;
this.nullAsEmptyCollection = nullAsEmptyCollection;
}
/**
* Convert the given text value to a Collection with a single element.
*/
@Override
public void setAsText(String text) throws IllegalArgumentException {
setValue(text);
}
/**
* Convert the given value to a Collection of the target type.
*/
@Override
@SuppressWarnings("unchecked")
public void setValue(Object value) {
if (value == null && this.nullAsEmptyCollection) {
super.setValue(createCollection(this.collectionType, 0));
}
else if (value == null || (this.collectionType.isInstance(value) && !alwaysCreateNewCollection())) {
// Use the source value as-is, as it matches the target type.
super.setValue(value);
}
else if (value instanceof Collection) {
// Convert Collection elements.
Collection source = (Collection) value;
Collection target = createCollection(this.collectionType, source.size());
for (Object elem : source) {
target.add(convertElement(elem));
}
super.setValue(target);
}
else if (value.getClass().isArray()) {
// Convert array elements to Collection elements.
int length = Array.getLength(value);
Collection target = createCollection(this.collectionType, length);
for (int i = 0; i < length; i++) {
target.add(convertElement(Array.get(value, i)));
}
super.setValue(target);
}
else {
// A plain value: convert it to a Collection with a single element.
Collection target = createCollection(this.collectionType, 1);
target.add(convertElement(value));
super.setValue(target);
}
}
/**
* Create a Collection of the given type, with the given
* initial capacity (if supported by the Collection type).
* @param collectionType a sub-interface of Collection
* @param initialCapacity the initial capacity
* @return the new Collection instance
*/
protected Collection createCollection(Class collectionType, int initialCapacity) {
if (!collectionType.isInterface()) {
try {
return (Collection) collectionType.newInstance();
}
catch (Exception ex) {
throw new IllegalArgumentException(
"Could not instantiate collection class [" + collectionType.getName() + "]: " + ex.getMessage());
}
}
else if (List.class.equals(collectionType)) {
return new ArrayList(initialCapacity);
}
else if (SortedSet.class.equals(collectionType)) {
return new TreeSet();
}
else {
return new LinkedHashSet(initialCapacity);
}
}
/**
* Return whether to always create a new Collection,
* even if the type of the passed-in Collection already matches.
* <p>Default is "false"; can be overridden to enforce creation of a
* new Collection, for example to convert elements in any case.
* @see #convertElement
*/
protected boolean alwaysCreateNewCollection() {
return false;
}
/**
* Hook to convert each encountered Collection/array element.
* The default implementation simply returns the passed-in element as-is.
* <p>Can be overridden to perform conversion of certain elements,
* for example String to Integer if a String array comes in and
* should be converted to a Set of Integer objects.
* <p>Only called if actually creating a new Collection!
* This is by default not the case if the type of the passed-in Collection
* already matches. Override {@link #alwaysCreateNewCollection()} to
* enforce creating a new Collection in every case.
* @param element the source element
* @return the element to be used in the target Collection
* @see #alwaysCreateNewCollection()
*/
protected Object convertElement(Object element) {
return element;
}
/**
* This implementation returns <code>null</code> to indicate that
* there is no appropriate text representation.
*/
@Override
public String getAsText() {
return null;
}
}
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