Spring Framework example source code file (CustomMapEditor.java)

This example Spring Framework source code file (CustomMapEditor.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Spring Framework tags/keywords

bean, custommapeditor, custommapeditor, illegalargumentexception, illegalargumentexception, iterator, javabean, linkedhashmap, map, map, object, object, propertyeditorsupport, string, treemap, util, value

The Spring Framework CustomMapEditor.java source code

/*
 * Copyright 2002-2007 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.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.SortedMap;
import java.util.TreeMap;

/**
 * Property editor for Maps, converting any source Map
 * to a given target Map type.
 *
 * @author Juergen Hoeller
 * @since 2.0.1
 * @see java.util.Map
 * @see java.util.SortedMap
 */
public class CustomMapEditor extends PropertyEditorSupport {

	private final Class mapType;

	private final boolean nullAsEmptyMap;


	/**
	 * Create a new CustomMapEditor for the given target type,
	 * keeping an incoming <code>null as-is.
	 * @param mapType the target type, which needs to be a
	 * sub-interface of Map or a concrete Map class
	 * @see java.util.Map
	 * @see java.util.HashMap
	 * @see java.util.TreeMap
	 * @see java.util.LinkedHashMap
	 */
	public CustomMapEditor(Class mapType) {
		this(mapType, false);
	}

	/**
	 * Create a new CustomMapEditor 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 Map type or an array, it will be converted
	 * to a default implementation of the given Map type.
	 * If the value is anything else, a target Map with that single
	 * value will be created.
	 * <p>The default Map implementations are: TreeMap for SortedMap,
	 * and LinkedHashMap for Map.
	 * @param mapType the target type, which needs to be a
	 * sub-interface of Map or a concrete Map class
	 * @param nullAsEmptyMap ap whether to convert an incoming <code>null
	 * value to an empty Map (of the appropriate type)
	 * @see java.util.Map
	 * @see java.util.TreeMap
	 * @see java.util.LinkedHashMap
	 */
	public CustomMapEditor(Class mapType, boolean nullAsEmptyMap) {
		if (mapType == null) {
			throw new IllegalArgumentException("Map type is required");
		}
		if (!Map.class.isAssignableFrom(mapType)) {
			throw new IllegalArgumentException(
					"Map type [" + mapType.getName() + "] does not implement [java.util.Map]");
		}
		this.mapType = mapType;
		this.nullAsEmptyMap = nullAsEmptyMap;
	}


	/**
	 * Convert the given text value to a Map with a single element.
	 */
	public void setAsText(String text) throws IllegalArgumentException {
		setValue(text);
	}

	/**
	 * Convert the given value to a Map of the target type.
	 */
	public void setValue(Object value) {
		if (value == null && this.nullAsEmptyMap) {
			super.setValue(createMap(this.mapType, 0));
		}
		else if (value == null || (this.mapType.isInstance(value) && !alwaysCreateNewMap())) {
			// Use the source value as-is, as it matches the target type.
			super.setValue(value);
		}
		else if (value instanceof Map) {
			// Convert Map elements.
			Map source = (Map) value;
			Map target = createMap(this.mapType, source.size());
			for (Iterator it = source.entrySet().iterator(); it.hasNext();) {
				Map.Entry entry = (Map.Entry) it.next();
				target.put(convertKey(entry.getKey()), convertValue(entry.getValue()));
			}
			super.setValue(target);
		}
		else {
			throw new IllegalArgumentException("Value cannot be converted to Map: " + value);
		}
	}

	/**
	 * Create a Map of the given type, with the given
	 * initial capacity (if supported by the Map type).
	 * @param mapType a sub-interface of Map
	 * @param initialCapacity the initial capacity
	 * @return the new Map instance
	 */
	protected Map createMap(Class mapType, int initialCapacity) {
		if (!mapType.isInterface()) {
			try {
				return (Map) mapType.newInstance();
			}
			catch (Exception ex) {
				throw new IllegalArgumentException(
						"Could not instantiate map class [" + mapType.getName() + "]: " + ex.getMessage());
			}
		}
		else if (SortedMap.class.equals(mapType)) {
			return new TreeMap();
		}
		else {
			return new LinkedHashMap(initialCapacity);
		}
	}

	/**
	 * Return whether to always create a new Map,
	 * even if the type of the passed-in Map already matches.
	 * <p>Default is "false"; can be overridden to enforce creation of a
	 * new Map, for example to convert elements in any case.
	 * @see #convertKey
	 * @see #convertValue
	 */
	protected boolean alwaysCreateNewMap() {
		return false;
	}

	/**
	 * Hook to convert each encountered Map key.
	 * The default implementation simply returns the passed-in key as-is.
	 * <p>Can be overridden to perform conversion of certain keys,
	 * for example from String to Integer.
	 * <p>Only called if actually creating a new Map!
	 * This is by default not the case if the type of the passed-in Map
	 * already matches. Override {@link #alwaysCreateNewMap()} to
	 * enforce creating a new Map in every case.
	 * @param key the source key
	 * @return the key to be used in the target Map
	 * @see #alwaysCreateNewMap
	 */
	protected Object convertKey(Object key) {
		return key;
	}

	/**
	 * Hook to convert each encountered Map value.
	 * The default implementation simply returns the passed-in value as-is.
	 * <p>Can be overridden to perform conversion of certain values,
	 * for example from String to Integer.
	 * <p>Only called if actually creating a new Map!
	 * This is by default not the case if the type of the passed-in Map
	 * already matches. Override {@link #alwaysCreateNewMap()} to
	 * enforce creating a new Map in every case.
	 * @param value the source value
	 * @return the value to be used in the target Map
	 * @see #alwaysCreateNewMap
	 */
	protected Object convertValue(Object value) {
		return value;
	}


	/**
	 * This implementation returns <code>null to indicate that
	 * there is no appropriate text representation.
	 */
	public String getAsText() {
		return null;
	}

}