01: /* ================================================================
02: * Cewolf : Chart enabling Web Objects Framework
03: * ================================================================
04: *
05: * Project Info: http://cewolf.sourceforge.net
06: * Project Lead: Guido Laures (guido@laures.de);
07: *
08: * (C) Copyright 2002, by Guido Laures
09: *
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.
13: *
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.
17: *
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.
21: */
22:
23: package de.laures.cewolf;
24:
25: import java.io.Serializable;
26: import java.util.Date;
27: import java.util.Map;
28:
29: /**
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
34: * @since 0.1
35: */
36: public interface DatasetProducer extends Serializable {
37:
38: /**
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.
42: */
43: public static final String PRODUCER_ATTRIBUTE_NAME = "de.laures.cewolf.DatasetProducer.id";
44:
45: /**
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
56: * @since 0.2
57: */
58: Object produceDataset(Map params) throws DatasetProduceException;
59:
60: /**
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>
73: * otherwise
74: * @since 0.9
75: */
76: boolean hasExpired(Map params, Date since);
77:
78: /**
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
83: * @since 0.9
84: */
85: String getProducerId();
86:
87: }
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