Java tutorial
/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You 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.apache.commons.beanutils; import java.util.Map; import java.util.List; import java.util.ArrayList; import java.util.Set; import java.util.HashSet; import java.util.Iterator; import java.util.Collection; import java.util.Collections; /** * <p>Decorates a {@link DynaBean} to provide <code>Map</code> behaviour.</p> * * <p>The motivation for this implementation is to provide access to {@link DynaBean} * properties in technologies that are unaware of BeanUtils and {@link DynaBean}s - * such as the expression languages of JSTL and JSF.</p> * * <p>This can be achieved either by wrapping the {@link DynaBean} prior to * providing it to the technolody to process or by providing a <code>Map</code> * accessor method on the DynaBean implementation: * <pre><code> * public Map getMap() { * return new DynaBeanMapDecorator(this); * }</code></pre> * </ul> * </p> * * <p>This, for example, could be used in JSTL in the following way to access * a DynaBean's <code>fooProperty</code>: * <ul><li><code>${myDynaBean.<b>map</b>.fooProperty}</code></li></ul> * </p> * * <h3>Usage</h3> * * <p>To decorate a {@link DynaBean} simply instantiate this class with the * target {@link DynaBean}:</p> * * <ul><li><code>Map fooMap = new DynaBeanMapDecorator(fooDynaBean);</code></li></ul> * * <p>The above example creates a <b><i>read only</i></b> <code>Map</code>. * To create a <code>Map</code> which can be modified, construct a * <code>DynaBeanMapDecorator</code> with the <b><i>read only</i></b> * attribute set to <code>false</code>:</p> * * <ul><li><code>Map fooMap = new DynaBeanMapDecorator(fooDynaBean, false);</code></li></ul> * * <h3>Limitations</h3> * <p>In this implementation the <code>entrySet()</code>, <code>keySet()</code> * and <code>values()</code> methods create an <b><i>unmodifiable</i></b> * <code>Set</code> and it does not support the Map's <code>clear()</code> * and <code>remove()</code> operations.</p> * * @since BeanUtils 1.8.0 * @version $Revision: 546471 $ $Date: 2007-06-12 13:57:20 +0100 (Tue, 12 Jun 2007) $ */ public class DynaBeanMapDecorator implements Map { private DynaBean dynaBean; private boolean readOnly; private transient Set keySet; // ------------------- Constructors ---------------------------------- /** * Constructs a read only Map for the specified * {@link DynaBean}. * * @param dynaBean The dyna bean being decorated * @throws IllegalArgumentException if the {@link DynaBean} is null. */ public DynaBeanMapDecorator(DynaBean dynaBean) { this(dynaBean, true); } /** * Construct a Map for the specified {@link DynaBean}. * * @param dynaBean The dyna bean being decorated * @param readOnly <code>true</code> if the Mpa is read only * otherwise <code>false</code> * @throws IllegalArgumentException if the {@link DynaBean} is null. */ public DynaBeanMapDecorator(DynaBean dynaBean, boolean readOnly) { if (dynaBean == null) { throw new IllegalArgumentException("DynaBean is null"); } this.dynaBean = dynaBean; this.readOnly = readOnly; } // ------------------- public Methods -------------------------------- /** * Indicate whether the Map is read only. * * @return <code>true</code> if the Map is read only, * otherwise <code>false</code>. */ public boolean isReadOnly() { return readOnly; } // ------------------- java.util.Map Methods ------------------------- /** * clear() operation is not supported. * * @throws UnsupportedOperationException */ public void clear() { throw new UnsupportedOperationException(); } /** * Indicate whether the {@link DynaBean} contains a specified * value for one (or more) of its properties. * * @param key The {@link DynaBean}'s property name * @return <code>true</code> if one of the {@link DynaBean}'s * properties contains a specified value. */ public boolean containsKey(Object key) { DynaClass dynaClass = getDynaBean().getDynaClass(); DynaProperty dynaProperty = dynaClass.getDynaProperty(toString(key)); return (dynaProperty == null ? false : true); } /** * Indicates whether the decorated {@link DynaBean} contains * a specified value. * * @param value The value to check for. * @return <code>true</code> if one of the the {@link DynaBean}'s * properties contains the specified value, otherwise * <code>false</code>. */ public boolean containsValue(Object value) { DynaProperty[] properties = getDynaProperties(); for (int i = 0; i < properties.length; i++) { String key = properties[i].getName(); Object prop = getDynaBean().get(key); if (value == null) { if (prop == null) { return true; } } else { if (value.equals(prop)) { return true; } } } return false; } /** * <p>Returns the Set of the property/value mappings * in the decorated {@link DynaBean}.</p> * * <p>Each element in the Set is a <code>Map.Entry</code> * type.</p> * * @return An unmodifiable set of the DynaBean * property name/value pairs */ public Set entrySet() { DynaProperty[] properties = getDynaProperties(); Set set = new HashSet(properties.length); for (int i = 0; i < properties.length; i++) { String key = properties[i].getName(); Object value = getDynaBean().get(key); set.add(new MapEntry(key, value)); } return Collections.unmodifiableSet(set); } /** * Return the value for the specified key from * the decorated {@link DynaBean}. * * @param key The {@link DynaBean}'s property name * @return The value for the specified property. */ public Object get(Object key) { return getDynaBean().get(toString(key)); } /** * Indicate whether the decorated {@link DynaBean} has * any properties. * * @return <code>true</code> if the {@link DynaBean} has * no properties, otherwise <code>false</code>. */ public boolean isEmpty() { return (getDynaProperties().length == 0); } /** * <p>Returns the Set of the property * names in the decorated {@link DynaBean}.</p> * * <p><b>N.B.</b>For {@link DynaBean}s whose associated {@link DynaClass} * is a {@link MutableDynaClass} a new Set is created every * time, otherwise the Set is created only once and cached.</p> * * @return An unmodifiable set of the {@link DynaBean}s * property names. */ public Set keySet() { if (keySet != null) { return keySet; } // Create a Set of the keys DynaProperty[] properties = getDynaProperties(); Set set = new HashSet(properties.length); for (int i = 0; i < properties.length; i++) { set.add(properties[i].getName()); } set = Collections.unmodifiableSet(set); // Cache the keySet if Not a MutableDynaClass DynaClass dynaClass = getDynaBean().getDynaClass(); if (!(dynaClass instanceof MutableDynaClass)) { keySet = set; } return set; } /** * Set the value for the specified property in * the decorated {@link DynaBean}. * * @param key The {@link DynaBean}'s property name * @param value The value for the specified property. * @return The previous property's value. * @throws UnsupportedOperationException if * <code>isReadOnly()</code> is true. */ public Object put(Object key, Object value) { if (isReadOnly()) { throw new UnsupportedOperationException("Map is read only"); } String property = toString(key); Object previous = getDynaBean().get(property); getDynaBean().set(property, value); return previous; } /** * Copy the contents of a Map to the decorated {@link DynaBean}. * * @param map The Map of values to copy. * @throws UnsupportedOperationException if * <code>isReadOnly()</code> is true. */ public void putAll(Map map) { if (isReadOnly()) { throw new UnsupportedOperationException("Map is read only"); } Iterator keys = map.keySet().iterator(); while (keys.hasNext()) { Object key = keys.next(); put(key, map.get(key)); } } /** * remove() operation is not supported. * * @param key The {@link DynaBean}'s property name * @return the value removed * @throws UnsupportedOperationException */ public Object remove(Object key) { throw new UnsupportedOperationException(); } /** * Returns the number properties in the decorated * {@link DynaBean}. * @return The number of properties. */ public int size() { return getDynaProperties().length; } /** * Returns the set of property values in the * decorated {@link DynaBean}. * * @return Unmodifiable collection of values. */ public Collection values() { DynaProperty[] properties = getDynaProperties(); List values = new ArrayList(properties.length); for (int i = 0; i < properties.length; i++) { String key = properties[i].getName(); Object value = getDynaBean().get(key); values.add(value); } return Collections.unmodifiableList(values); } // ------------------- protected Methods ----------------------------- /** * Provide access to the underlying {@link DynaBean} * this Map decorates. * * @return the decorated {@link DynaBean}. */ public DynaBean getDynaBean() { return dynaBean; } // ------------------- private Methods ------------------------------- /** * Convenience method to retrieve the {@link DynaProperty}s * for this {@link DynaClass}. * * @return The an array of the {@link DynaProperty}s. */ private DynaProperty[] getDynaProperties() { return getDynaBean().getDynaClass().getDynaProperties(); } /** * Convenience method to convert an Object * to a String. * * @param obj The Object to convert * @return String representation of the object */ private String toString(Object obj) { return (obj == null ? null : obj.toString()); } /** * Map.Entry implementation. */ private static class MapEntry implements Map.Entry { private Object key; private Object value; MapEntry(Object key, Object value) { this.key = key; this.value = value; } public boolean equals(Object o) { if (!(o instanceof Map.Entry)) { return false; } Map.Entry e = (Map.Entry) o; return ((key.equals(e.getKey())) && (value == null ? e.getValue() == null : value.equals(e.getValue()))); } public int hashCode() { return key.hashCode() + (value == null ? 0 : value.hashCode()); } public Object getKey() { return key; } public Object getValue() { return value; } public Object setValue(Object value) { throw new UnsupportedOperationException(); } } }