Java tutorial
/* * Copyright 2010-2011 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 com.google.code.pathlet.web.ognl.impl; import java.util.ArrayList; import java.util.Collection; import java.util.Iterator; import java.util.Map; import ognl.TypeConverter; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import com.google.code.pathlet.web.ognl.ConvertException; /** * A simple list that guarantees that inserting and retrieving objects will always work regardless * of the current size of the list. Upon insertion, type conversion is also performed if necessary. * Empty beans will be created to fill the gap between the current list size and the requested index * using ObjectFactory's {@link ObjectFactory#buildBean(Class,java.util.Map) buildBean} method. * * @author Charlie Zhang */ @SuppressWarnings({ "rawtypes", "serial" }) public class IncreasableList extends ArrayList { private static final Log log = LogFactory.getLog(IncreasableList.class); private Class clazz; private TypeConverter conv; private Map context; public IncreasableList(Map context, TypeConverter conv, Class clazz) { this.context = context; this.conv = conv; this.clazz = clazz; } public IncreasableList(Map context, TypeConverter conv, Class clazz, int initialCapacity) { super(initialCapacity); this.context = context; this.clazz = clazz; this.conv = conv; } /** * Inserts the specified element at the specified position in this list. Shifts the element * currently at that position (if any) and any subsequent elements to the right (adds one to * their indices). * <p/> * This method is guaranteed to work since it will create empty beans to fill the gap between * the current list size and the requested index to enable the element to be set. This method * also performs any necessary type conversion. * * @param index index at which the specified element is to be inserted. * @param element element to be inserted. */ @Override public void add(int index, Object element) { if (index >= this.size()) { get(index); } element = convert(element); super.add(index, element); } /** * Appends the specified element to the end of this list. * <p/> * This method performs any necessary type conversion. * * @param element element to be appended to this list. * @return <tt>true</tt> (as per the general contract of Collection.add). */ @Override public boolean add(Object element) { element = convert(element); return super.add(element); } /** * Appends all of the elements in the specified Collection to the end of this list, in the order * that they are returned by the specified Collection's Iterator. The behavior of this * operation is undefined if the specified Collection is modified while the operation is in * progress. (This implies that the behavior of this call is undefined if the specified * Collection is this list, and this list is nonempty.) * <p/> * This method performs any necessary type conversion. * * @param c the elements to be inserted into this list. * @return <tt>true</tt> if this list changed as a result of the call. * @throws NullPointerException if the specified collection is null. */ @Override public boolean addAll(Collection c) { if (c == null) { throw new NullPointerException("Collection to add is null"); } for (Object aC : c) { add(aC); } return true; } /** * Inserts all of the elements in the specified Collection into this list, starting at the * specified position. Shifts the element currently at that position (if any) and any * subsequent elements to the right (increases their indices). The new elements will appear in * the list in the order that they are returned by the specified Collection's iterator. * <p/> * This method is guaranteed to work since it will create empty beans to fill the gap between * the current list size and the requested index to enable the element to be set. This method * also performs any necessary type conversion. * * @param index index at which to insert first element from the specified collection. * @param c elements to be inserted into this list. * @return <tt>true</tt> if this list changed as a result of the call. */ @Override public boolean addAll(int index, Collection c) { if (c == null) { throw new NullPointerException("Collection to add is null"); } boolean trim = false; if (index >= this.size()) { trim = true; } for (Iterator it = c.iterator(); it.hasNext(); index++) { add(index, it.next()); } if (trim) { remove(this.size() - 1); } return true; } /** * Returns the element at the specified position in this list. * <p/> * An object is guaranteed to be returned since it will create empty beans to fill the gap * between the current list size and the requested index. * * @param index index of element to return. * @return the element at the specified position in this list. */ @Override public synchronized Object get(int index) { while (index >= this.size()) { try { this.add(clazz.newInstance()); } catch (Exception e) { throw new ConvertException(e); } } return super.get(index); } /** * Replaces the element at the specified position in this list with the specified element. * <p/> * This method is guaranteed to work since it will create empty beans to fill the gap between * the current list size and the requested index to enable the element to be set. This method * also performs any necessary type conversion. * * @param index index of element to replace. * @param element element to be stored at the specified position. * @return the element previously at the specified position. */ @Override public Object set(int index, Object element) { if (index >= this.size()) { get(index); } element = convert(element); return super.set(index, element); } private Object convert(Object element) { if ((element != null) && !clazz.isAssignableFrom(element.getClass())) { // convert to correct type if (log.isDebugEnabled()) { log.debug("Converting from " + element.getClass().getName() + " to " + clazz.getName()); } element = conv.convertValue(context, null, null, null, element, clazz); } return element; } @Override public boolean contains(Object element) { element = convert(element); return super.contains(element); } }