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Java > Open Source Codes > org > archive > crawler > deciderules > DecideRule


1 /* DecideRule
2 *
3 * $Id: DecideRule.java,v 1.9.4.1 2007/01/13 01:31:13 stack-sf Exp $
4 *
5 * Created on Mar 3, 2005
6 *
7 * Copyright (C) 2005 Internet Archive.
8 *
9 * This file is part of the Heritrix web crawler (crawler.archive.org).
10 *
11 * Heritrix is free software; you can redistribute it and/or modify
12 * it under the terms of the GNU Lesser Public License as published by
13 * the Free Software Foundation; either version 2.1 of the License, or
14 * any later version.
15 *
16 * Heritrix is distributed in the hope that it will be useful,
17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 * GNU Lesser Public License for more details.
20 *
21 * You should have received a copy of the GNU Lesser Public License
22 * along with Heritrix; if not, write to the Free Software
23 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
24 */
25 package org.archive.crawler.deciderules;
26
27 import org.archive.crawler.framework.CrawlController;
28 import org.archive.crawler.settings.ModuleType;
29
30
31 /**
32  * Interface for rules which, given an object to evaluate,
33  * respond with a decision: {@link DecideRule#ACCEPT},
34  * {@link DecideRule#REJECT}, or
35  * {@link DecideRule#PASS}.
36  *
37  * Rules return {@link #PASS} by default.
38  *
39  * @author gojomo
40  * @see org.archive.crawler.deciderules.DecideRuleSequence
41  */
42 public class DecideRule extends ModuleType {
43
44     private static final long serialVersionUID = 3437522810581532520L;
45     // enumeration of 'actions'
46 public static final String JavaDoc ACCEPT = "ACCEPT";
47     public static final String JavaDoc REJECT = "REJECT";
48     public static final String JavaDoc PASS = "PASS";
49
50     /**
51      * Constructor.
52      * @param name Name of this rule.
53      */
54     public DecideRule(String JavaDoc name) {
55         super(name);
56     }
57
58     /**
59      * Make decision on passed <code>object</code>.
60      * @param object Object to rule on.
61      * @return {@link #ACCEPT}, {@link #REJECT}, or {@link #PASS}.
62      */
63     public Object JavaDoc decisionFor(Object JavaDoc object) {
64         return PASS;
65     }
66
67     /**
68      * If this rule is "one-way" -- can only return a single
69      * possible decision other than PASS -- return that
70      * decision. Otherwise return null. Most rules will be
71      * one-way.
72      * @param object
73      *
74      * @return the one decision other than PASS this rule might
75      * return, if there is only one
76      */
77     public Object JavaDoc singlePossibleNonPassDecision(Object JavaDoc object) {
78         // by default, don't assume one-way
79 return null;
80     }
81     
82     /**
83      * Respond to a settings update, refreshing any internal settings-derived
84      * state.
85      *
86      * This method gives implementors a chance to refresh internal state
87      * after a settings change. Normally new settings are picked up w/o
88      * the need of work on the part of settings' clients but some facilities
89      * -- for example, Surt classes need to sort submissions into
90      * common-prefix-coalesced collection of Surt prefixes, or,
91      * settings changes that alter external file or seeds/directives
92      * references -- need to be flagged so they can take
93      * compensatory action.
94      */
95     public void kickUpdate() {
96         // by default do nothing
97 }
98     
99     /**
100      * Get the controller object.
101      *
102      * @return the controller object.
103      */
104     public CrawlController getController() {
105         return getSettingsHandler().getOrder().getController();
106     }
107 }
108
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