1 /* ================================================================
2 * Cewolf : Chart enabling Web Objects Framework
3 * ================================================================
5 * Project Info: http://cewolf.sourceforge.net
6 * Project Lead: Guido Laures (guido@laures.de);
8 * (C) Copyright 2002, by Guido Laures
10 * This library is free software; you can redistribute it and/or modify it under the terms
11 * of the GNU Lesser General Public License as published by the Free Software Foundation;
12 * either version 2.1 of the License, or (at your option) any later version.
14 * This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
15 * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
16 * See the GNU Lesser General Public License for more details.
18 * You should have received a copy of the GNU Lesser General Public License along with this
19 * library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
20 * Boston, MA 02111-1307, USA.
23 package de.laures.cewolf;
25 import java.io.Serializable;
26 import java.util.Date;
30 * Produces a {@link org.jfree.data.Dataset} which will be rendered
31 * as a chart afterwards.
32 * @see org.jfree.data.Dataset
33 * @author Guido Laures
36 public interface DatasetProducer extends Serializable {
39 * By default the the name of the JSP attribute
40 * holding the producer instance is passed to the
41 * produceDataset method as a prameter.
43 public static final String PRODUCER_ATTRIBUTE_NAME = "de.laures.cewolf.DatasetProducer.id";
46 * Produces a {@link org.jfree.data.Dataset} object.
47 * @param params additional params for the dataset production. All elements
48 * of this HashMap are of type <code>java.io.Serializable</code>. This is
49 * necessary to ensure the the serialization of the dataset producer into
50 * the http session. To provide a producer with additional production
51 * parameters the <param> tag is used (see tag library documentation).
52 * It is recommended to synchronize implementations of this method to avoid
53 * concurrency problems.
54 * @return an object of type <code>org.jfree.data.Dataset</code>.
55 * @throws DatasetProduceException if an error occured during production
58 Object produceDataset(Map params) throws DatasetProduceException;
61 * This method is called by the Cewolf framework to check if a formerly
62 * produced data can be reused. If the data which had already been used
63 * for chart rendering is still valid this method should return <code>true</code>.
64 * If possible the Cewolf framework will try to reuse the rendered chart
65 * image. If this is not possible because of some circumstances (e.g. the chart
66 * had been removed from the image cache) the produceDataset method is called afterwards.
67 * Therefore there is no guarantee that the dataset production is always
68 * avoided if this method returns <code>true</true>.
69 * @param params the production parameters of the already produced data
70 * @param since the point in time when the already produced data had been produced
71 * @return <code>true</code> if the data which had been produced with the
72 * passed in parameters has expired since its creation, <code>false</code>
76 boolean hasExpired(Map params, Date since);
79 * Tis method returns a unique ID for a DatasetProducer from this class.
80 * Producers with the same ID are supposed to produce the same data when
81 * called with the same paramters.
82 * @return the unique ID for instances of this poducer class
85 String getProducerId();