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Java > Open Source Codes > org > codehaus > loom > components > classloader > PolicyClassLoader


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87 package org.codehaus.loom.components.classloader;
88
89 import java.io.IOException JavaDoc;
90 import java.net.URL JavaDoc;
91 import java.net.URLClassLoader JavaDoc;
92 import java.security.CodeSource JavaDoc;
93 import java.security.PermissionCollection JavaDoc;
94 import java.security.Policy JavaDoc;
95 import java.util.Enumeration JavaDoc;
96 import org.codehaus.dna.LogEnabled;
97 import org.codehaus.dna.Logger;
98
99 /**
100  * Classloader that uses a specified {@link Policy} object rather than system
101  * {@link Policy} object.
102  *
103  * <p>Note that parts of this were cloned from other projects</p>
104  *
105  * @author Peter Donald
106  */
107 class PolicyClassLoader
108     extends URLClassLoader JavaDoc
109     implements LogEnabled
110 {
111     ///Policy to use to define permissions for classes loaded in classloader
112 private final Policy JavaDoc m_policy;
113
114     ///Logger to use when reporting information
115 private Logger m_logger;
116
117     /**
118      * Construct a ClassLoader using specified URLs, parent ClassLoader and
119      * Policy object.
120      *
121      * @param urls the URLs to load resources from
122      * @param parent the parent ClassLoader
123      * @param policy the Policy object
124      */
125     PolicyClassLoader( final URL JavaDoc[] urls,
126                        final ClassLoader JavaDoc parent,
127                        final Policy JavaDoc policy )
128     {
129         super( urls, parent );
130         if( null == policy )
131         {
132             throw new NullPointerException JavaDoc( "policy" );
133         }
134         m_policy = policy;
135     }
136
137     public void enableLogging( final Logger logger )
138     {
139         m_logger = logger;
140     }
141
142     /**
143      * Overide findClass to log debugging information indicating that a class is
144      * being loaded from application ClassLoader.
145      *
146      * @param name the name of class ot load
147      * @return the Class loaded
148      * @throws ClassNotFoundException if can not find class
149      */
150     protected Class JavaDoc findClass( final String JavaDoc name )
151         throws ClassNotFoundException JavaDoc
152     {
153         if( m_logger.isDebugEnabled() )
154         {
155             m_logger.debug( "findClass(" + name + ")" );
156         }
157         return super.findClass( name );
158     }
159
160     /**
161      * Overide so we can have a per-application security policy with no
162      * side-effects to other applications.
163      *
164      * @param codeSource the codeSource to get permissions for
165      * @return the PermissionCollection
166      */
167     protected PermissionCollection JavaDoc getPermissions( final CodeSource JavaDoc codeSource )
168     {
169         if( m_logger.isDebugEnabled() )
170         {
171             m_logger.debug( "getPermissions(" + codeSource + ")" );
172         }
173         return m_policy.getPermissions( codeSource );
174     }
175
176     /**
177      * Return an enumeration of {@link URL}s representing all of the resources
178      * with the given name. If no resources with this name are found, return an
179      * empty enumeration.
180      *
181      * <p>Note that this method is overidden to provide debugging
182      * information.</p>
183      *
184      * @param name the name of resource to look for
185      * @return the Enumeration of resources
186      * @throws IOException if an input/output error occurs
187      */
188     public Enumeration JavaDoc findResources( final String JavaDoc name )
189         throws IOException JavaDoc
190     {
191         if( m_logger.isDebugEnabled() )
192         {
193             m_logger.debug( "findResources(" + name + ")" );
194         }
195
196         return super.findResources( name );
197     }
198
199     /**
200      * Find the resource in the ClassLoader. Return a {@link URL} object if
201      * found, otherwise return null if this resource cannot be found.
202      *
203      * <p>Note that this method is overidden to provide debugging
204      * information.</p>
205      *
206      * @param name the name of resource to look for
207      * @return the URL if found, else null
208      */
209     public URL JavaDoc findResource( final String JavaDoc name )
210     {
211         if( m_logger.isDebugEnabled() )
212         {
213             m_logger.debug( "findResource(" + name + ")" );
214         }
215
216         final URL JavaDoc url = super.findResource( name );
217
218         if( m_logger.isDebugEnabled() )
219         {
220             if( null != url )
221             {
222                 m_logger.debug( "Resource " + name + " located (" + url + ")" );
223             }
224             else
225             {
226                 m_logger.debug( "Resource " + name + " not located" );
227             }
228         }
229
230         return url;
231     }
232 }
233
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