001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.wicket.markup.repeater.data;
018
019import java.util.Iterator;
020
021import org.apache.wicket.markup.html.navigation.paging.IPageable;
022import org.apache.wicket.markup.repeater.AbstractPageableView;
023import org.apache.wicket.markup.repeater.RefreshingView;
024import org.apache.wicket.model.IModel;
025import org.apache.wicket.util.lang.Args;
026
027
028/**
029 * Base class for data views.
030 * 
031 * Data views aim to make it very simple to populate your repeating view from a database by
032 * utilizing {@link IDataProvider} to act as an interface between the database and the dataview.
033 * 
034 * @see IDataProvider
035 * @see DataView
036 * @see IPageable
037 * @see RefreshingView
038 * 
039 * @author Igor Vaynberg (ivaynberg)
040 * 
041 * @param <T>
042 *            Model object type
043 */
044public abstract class DataViewBase<T> extends AbstractPageableView<T>
045{
046        private static final long serialVersionUID = 1L;
047        private final IDataProvider<T> dataProvider;
048
049        /**
050         * @param id
051         *            component id
052         * @param dataProvider
053         *            data provider
054         */
055        public DataViewBase(String id, IDataProvider<T> dataProvider)
056        {
057                super(id);
058
059                this.dataProvider = Args.notNull(dataProvider, "dataProvider");
060        }
061
062        /**
063         * @return data provider associated with this view
064         */
065        protected final IDataProvider<T> internalGetDataProvider()
066        {
067                return dataProvider;
068        }
069
070
071        @Override
072        protected final Iterator<IModel<T>> getItemModels(long offset, long count)
073        {
074                return new ModelIterator<T>(internalGetDataProvider(), offset, count);
075        }
076
077        /**
078         * Helper class that converts input from IDataProvider to an iterator over view items.
079         * 
080         * @author Igor Vaynberg (ivaynberg)
081         * 
082         * @param <T>
083         *            Model object type
084         */
085        private static final class ModelIterator<T> implements Iterator<IModel<T>>
086        {
087                private final Iterator<? extends T> items;
088                private final IDataProvider<T> dataProvider;
089                private final long max;
090                private long index;
091
092                /**
093                 * Constructor
094                 * 
095                 * @param dataProvider
096                 *            data provider
097                 * @param offset
098                 *            index of first item
099                 * @param count
100                 *            max number of items to return
101                 */
102                public ModelIterator(IDataProvider<T> dataProvider, long offset, long count)
103                {
104                        this.dataProvider = dataProvider;
105                        max = count;
106
107                        items = count > 0 ? dataProvider.iterator(offset, count) : null;
108                }
109
110                /**
111                 * @see java.util.Iterator#remove()
112                 */
113                @Override
114                public void remove()
115                {
116                        throw new UnsupportedOperationException();
117                }
118
119                /**
120                 * @see java.util.Iterator#hasNext()
121                 */
122                @Override
123                public boolean hasNext()
124                {
125                        return items != null && items.hasNext() && (index < max);
126                }
127
128                /**
129                 * @see java.util.Iterator#next()
130                 */
131                @Override
132                public IModel<T> next()
133                {
134                        index++;
135                        return dataProvider.model(items.next());
136                }
137        }
138
139        @Override
140        protected final long internalGetItemCount()
141        {
142                return internalGetDataProvider().size();
143        }
144
145        /**
146         * @see org.apache.wicket.markup.repeater.AbstractPageableView#onDetach()
147         */
148        @Override
149        protected void onDetach()
150        {
151                dataProvider.detach();
152                super.onDetach();
153        }
154}