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Java > Open Source Codes > com > opensymphony > module > sitemesh > Factory


1 /*
2  * Title: Factory
3  * Description:
4  *
5  * This software is published under the terms of the OpenSymphony Software
6  * License version 1.1, of which a copy has been included with this
7  * distribution in the LICENSE.txt file.
8  */
9
10 package com.opensymphony.module.sitemesh;
11
12 import com.opensymphony.module.sitemesh.factory.FactoryException;
13 import com.opensymphony.module.sitemesh.util.Container;
14
15 import javax.naming.InitialContext JavaDoc;
16 import javax.rmi.PortableRemoteObject JavaDoc;
17 import java.lang.reflect.Constructor JavaDoc;
18
19 /**
20  * Factory responsible for creating appropriate instances of implementations.
21  * This is specific to a web context and is obtained through {@link #getInstance(com.opensymphony.module.sitemesh.Config)}.
22  *
23  * <p>The actual Factory method used is determined by the enviroment entry <code>sitemesh.factory</code>.
24  * If this doesn't exist, it defaults to {@link com.opensymphony.module.sitemesh.factory.DefaultFactory} .</p>
25  *
26  * @author <a HREF="mailto:joe@truemesh.com">Joe Walnes</a>
27  * @version $Revision: 1.5 $
28  */
29 public abstract class Factory {
30     /** Web context lookup key */
31     private static final String JavaDoc SITEMESH_FACTORY = "sitemesh.factory";
32
33     /**
34      * Entry-point for obtaining singleton instance of Factory. The default factory class
35      * that will be instantiated can be overridden with the environment
36      * entry <code>sitemesh.factory</code>.
37      */
38     public static Factory getInstance(Config config) {
39         Factory instance = (Factory)config.getServletContext().getAttribute(SITEMESH_FACTORY);
40         if (instance == null) {
41             String JavaDoc factoryClass = getEnvEntry("sitemesh.factory", "com.opensymphony.module.sitemesh.factory.DefaultFactory");
42             try {
43                 Class JavaDoc cls;
44                 try {
45                     cls = Class.forName(factoryClass);
46                 }
47                 catch (NoClassDefFoundError JavaDoc e) {
48                     cls = Class.forName(factoryClass, true, Thread.currentThread().getContextClassLoader());
49                 }
50
51                 Constructor JavaDoc con = cls.getConstructor(new Class JavaDoc[] { Config.class });
52                 instance = (Factory)con.newInstance(new Config[] { config });
53                 config.getServletContext().setAttribute(SITEMESH_FACTORY, instance);
54             }
55             catch (Exception JavaDoc e) {
56                 report("Cannot construct Factory : " + factoryClass, e);
57             }
58         }
59         return instance;
60     }
61
62     /** Return instance of DecoratorMapper. */
63     public abstract DecoratorMapper getDecoratorMapper();
64
65     /**
66      * Create a PageParser suitable for the given content-type.
67      *
68      * <p>For example, if the supplied parameter is <code>text/html</code>
69      * a parser shall be returned that can parse HTML accordingly.</p> Never returns null.
70      *
71      * @param contentType The MIME content-type of the data to be parsed
72      * @return Appropriate <code>PageParser</code> for reading data
73      *
74      */
75     public abstract PageParser getPageParser(String JavaDoc contentType);
76
77     /** Determine whether a Page of given content-type should be parsed or not. */
78     public abstract boolean shouldParsePage(String JavaDoc contentType);
79
80     /**
81      * Determine whether the given path should be excluded from decoration or not.
82      */
83     public abstract boolean isPathExcluded(String JavaDoc path);
84
85     /** Report a problem. */
86     protected static void report(String JavaDoc msg, Exception JavaDoc e) {
87         throw new FactoryException(msg, e);
88     }
89
90     /** Find String environment entry, or return default if not found. */
91     private static String JavaDoc getEnvEntry(String JavaDoc envEntry, String JavaDoc defaultValue) {
92         String JavaDoc result = null;
93         try {
94             if (Container.get() != Container.JRUN) {
95                 // TODO: JRun really isn't happy with this
96 InitialContext JavaDoc ctx = new InitialContext JavaDoc();
97                 Object JavaDoc o = ctx.lookup("java:comp/env/" + envEntry);
98                 ctx.close();
99                 result = (String JavaDoc)PortableRemoteObject.narrow(o, String JavaDoc.class); // rmi-iiop friendly.
100 }
101         }
102         catch (Exception JavaDoc e) { } // failed - don't moan, just return default.
103 return result == null || result.trim().length() == 0 ? defaultValue : result;
104     }
105 }
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