org.apache.wicket.markup.repeater.data.DataViewBase.java Source code

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Here is the source code for org.apache.wicket.markup.repeater.data.DataViewBase.java

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/*
 * 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.wicket.markup.repeater.data;

import java.util.Iterator;

import org.apache.wicket.markup.html.navigation.paging.IPageable;
import org.apache.wicket.markup.repeater.AbstractPageableView;
import org.apache.wicket.markup.repeater.RefreshingView;
import org.apache.wicket.model.IModel;
import org.apache.wicket.util.lang.Args;

/**
 * Base class for data views.
 * 
 * Data views aim to make it very simple to populate your repeating view from a database by
 * utilizing {@link IDataProvider} to act as an interface between the database and the dataview.
 * 
 * @see IDataProvider
 * @see DataView
 * @see IPageable
 * @see RefreshingView
 * 
 * @author Igor Vaynberg (ivaynberg)
 * 
 * @param <T>
 *            Model object type
 */
public abstract class DataViewBase<T> extends AbstractPageableView<T> {
    private static final long serialVersionUID = 1L;
    private final IDataProvider<T> dataProvider;

    /**
     * @param id
     *            component id
     * @param dataProvider
     *            data provider
     */
    public DataViewBase(String id, IDataProvider<T> dataProvider) {
        super(id);

        this.dataProvider = Args.notNull(dataProvider, "dataProvider");
    }

    /**
     * @return data provider associated with this view
     */
    protected final IDataProvider<T> internalGetDataProvider() {
        return dataProvider;
    }

    @Override
    protected final Iterator<IModel<T>> getItemModels(long offset, long count) {
        return new ModelIterator<T>(internalGetDataProvider(), offset, count);
    }

    /**
     * Helper class that converts input from IDataProvider to an iterator over view items.
     * 
     * @author Igor Vaynberg (ivaynberg)
     * 
     * @param <T>
     *            Model object type
     */
    private static final class ModelIterator<T> implements Iterator<IModel<T>> {
        private final Iterator<? extends T> items;
        private final IDataProvider<T> dataProvider;
        private final long max;
        private long index;

        /**
         * Constructor
         * 
         * @param dataProvider
         *            data provider
         * @param offset
         *            index of first item
         * @param count
         *            max number of items to return
         */
        public ModelIterator(IDataProvider<T> dataProvider, long offset, long count) {
            this.dataProvider = dataProvider;
            max = count;

            items = count > 0 ? dataProvider.iterator(offset, count) : null;
        }

        /**
         * @see java.util.Iterator#remove()
         */
        @Override
        public void remove() {
            throw new UnsupportedOperationException();
        }

        /**
         * @see java.util.Iterator#hasNext()
         */
        @Override
        public boolean hasNext() {
            return items != null && items.hasNext() && (index < max);
        }

        /**
         * @see java.util.Iterator#next()
         */
        @Override
        public IModel<T> next() {
            index++;
            return dataProvider.model(items.next());
        }
    }

    @Override
    protected final long internalGetItemCount() {
        return internalGetDataProvider().size();
    }

    /**
     * @see org.apache.wicket.markup.repeater.AbstractPageableView#onDetach()
     */
    @Override
    protected void onDetach() {
        dataProvider.detach();
        super.onDetach();
    }
}