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Java > Open Source Codes > bsh > classpath > BshClassLoader


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33
34 package bsh.classpath;
35
36 import java.net.*;
37 import java.util.*;
38 import java.io.*;
39 import bsh.BshClassManager;
40
41 /**
42     One of the things BshClassLoader does is to address a deficiency in
43     URLClassLoader that prevents us from specifying individual classes
44     via URLs.
45 */
46 public class BshClassLoader extends URLClassLoader
47 {
48     BshClassManager classManager;
49
50     /**
51         @param bases URLs JARClassLoader seems to require absolute paths
52     */
53     public BshClassLoader( BshClassManager classManager, URL [] bases ) {
54         super( bases );
55         this.classManager = classManager;
56     }
57
58     /**
59         @param bases URLs JARClassLoader seems to require absolute paths
60     */
61     public BshClassLoader( BshClassManager classManager, BshClassPath bcp ) {
62         this( classManager, bcp.getPathComponents() );
63     }
64
65     /**
66         For use by children
67         @param bases URLs JARClassLoader seems to require absolute paths
68     */
69     protected BshClassLoader( BshClassManager classManager ) {
70         this( classManager, new URL [] { } );
71     }
72
73     // public version of addURL
74 public void addURL( URL url ) {
75         super.addURL( url );
76     }
77
78     /**
79         This modification allows us to reload classes which are in the
80         Java VM user classpath. We search first rather than delegate to
81         the parent classloader (or bootstrap path) first.
82
83         An exception is for BeanShell core classes which are always loaded from
84         the same classloader as the interpreter.
85     */
86     public Class JavaDoc loadClass(String JavaDoc name, boolean resolve)
87         throws ClassNotFoundException JavaDoc
88     {
89         Class JavaDoc c = null;
90
91         /*
92             Check first for classes loaded through this loader.
93             The VM will not allow a class to be loaded twice.
94         */
95         c = findLoadedClass(name);
96         if ( c != null )
97             return c;
98
99 // This is copied from ClassManagerImpl
100 // We should refactor this somehow if it sticks around
101 if ( name.startsWith( ClassManagerImpl.BSH_PACKAGE ) )
102             try {
103                 return bsh.Interpreter.class.getClassLoader().loadClass( name );
104             } catch ( ClassNotFoundException JavaDoc e ) {}
105
106         /*
107             Try to find the class using our classloading mechanism.
108             Note: I wish we didn't have to catch the exception here... slow
109         */
110         try {
111             c = findClass( name );
112         } catch ( ClassNotFoundException JavaDoc e ) { }
113
114         if ( c == null )
115             throw new ClassNotFoundException JavaDoc("here in loaClass");
116
117         if ( resolve )
118             resolveClass( c );
119
120         return c;
121     }
122
123     /**
124         Find the correct source for the class...
125
126         Try designated loader if any
127         Try our URLClassLoader paths if any
128         Try base loader if any
129         Try system ???
130     */
131     // add some caching for not found classes?
132 protected Class JavaDoc findClass( String JavaDoc name )
133         throws ClassNotFoundException JavaDoc
134     {
135         // Deal with this cast somehow... maybe have this class use
136 // ClassManagerImpl type directly.
137 // Don't add the method to BshClassManager... it's really an impl thing
138 ClassManagerImpl bcm = (ClassManagerImpl)getClassManager();
139
140         // Should we try to load the class ourselves or delegate?
141 // look for overlay loader
142
143         // Deal with this cast somehow... maybe have this class use
144 // ClassManagerImpl type directly.
145 // Don't add the method to BshClassManager... it's really an impl thing
146 ClassLoader JavaDoc cl = bcm.getLoaderForClass( name );
147
148         Class JavaDoc c;
149
150         // If there is a designated loader and it's not us delegate to it
151 if ( cl != null && cl != this )
152             try {
153                 return cl.loadClass( name );
154             } catch ( ClassNotFoundException JavaDoc e ) {
155                 throw new ClassNotFoundException JavaDoc(
156                     "Designated loader could not find class: "+e );
157             }
158
159         // Let URLClassLoader try any paths it may have
160 if ( getURLs().length > 0 )
161             try {
162                 return super.findClass(name);
163             } catch ( ClassNotFoundException JavaDoc e ) {
164                 //System.out.println(
165 // "base loader here caught class not found: "+name );
166 }
167
168
169         // If there is a baseLoader and it's not us delegate to it
170 cl = bcm.getBaseLoader();
171
172         if ( cl != null && cl != this )
173             try {
174                 return cl.loadClass( name );
175             } catch ( ClassNotFoundException JavaDoc e ) { }
176
177         // Try system loader
178 return bcm.plainClassForName( name );
179     }
180
181     /*
182         The superclass does something like this
183
184         c = findLoadedClass(name);
185         if null
186             try
187                 if parent not null
188                     c = parent.loadClass(name, false);
189                 else
190                     c = findBootstrapClass(name);
191             catch ClassNotFoundException
192                 c = findClass(name);
193     */
194
195     BshClassManager getClassManager() { return classManager; }
196
197 }
198
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