DefaultClassLoaderManager


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87  package org.codehaus.loom.components.classloader;
88  
89  import java.io.File  ;
90  import java.net.URL  ;
91  import java.security.Policy  ;
92  import java.util.Collections  ;
93  import java.util.HashMap  ;
94  import java.util.Map  ;
95  
96  import org.codehaus.loom.classman.builder.LoaderBuilder;
97  import org.codehaus.loom.classman.builder.LoaderResolver;
98  import org.codehaus.loom.classman.metadata.ClassLoaderMetaData;
99  import org.codehaus.loom.classman.metadata.ClassLoaderSetMetaData;
100 import org.codehaus.loom.classman.metadata.FileSetMetaData;
101 import org.codehaus.loom.classman.metadata.JoinMetaData;
102 import org.codehaus.loom.classman.reader.ClassLoaderSetReader;
103 import org.codehaus.loom.classman.verifier.ClassLoaderVerifier;
104 import org.codehaus.loom.components.extensions.pkgmgr.ExtensionManager;
105 import org.codehaus.loom.components.extensions.pkgmgr.PackageManager;
106 import org.codehaus.loom.extension.Extension;
107 import org.codehaus.loom.interfaces.ClassLoaderManager;
108 import org.codehaus.loom.interfaces.ClassLoaderSet;
109 import org.codehaus.loom.xmlpolicy.builder.PolicyBuilder;
110 import org.codehaus.loom.xmlpolicy.metadata.PolicyMetaData;
111 import org.codehaus.loom.xmlpolicy.reader.PolicyReader;
112 import org.codehaus.spice.configkit.PropertyExpander;
113 import org.codehaus.dna.AbstractLogEnabled;
114 import org.codehaus.dna.Active;
115 import org.codehaus.dna.Composable;
116 import org.codehaus.dna.Configuration;
117 import org.codehaus.dna.ConfigurationException;
118 import org.codehaus.dna.MissingResourceException;
119 import org.codehaus.dna.ResourceLocator;
120 import org.codehaus.dna.impl.ConfigurationUtil;
121 import org.w3c.dom.Element  ;
122 
123 /**
124  * Component that creates and manages the {@link ClassLoader} for an application
125  * loaded out of a <tt>.sar</tt> deployment.
126  *
127  * <p>Currently it creates a policy based on the policy declaration in the
128  * configuration. It then just creates a URLClassLoader and populates it with
129  * the specified codebase {@link URL}s.</p>
130  *
131  * <p>In the future this class will scan the manifests for "Optional Packages"
132  * formely called "Extensions" which it will add to the {@link ClassLoader}</p>
133  *
134  * @author Peter Donald
135  * @see ClassLoaderManager
136  */
137 public class DefaultClassLoaderManager
138     extends AbstractLogEnabled
139     implements ClassLoaderManager, Composable, Active
140 {
141     /**
142      * Constant for name of element that indicates custom classloader tree to
143      * define.
144      */
145     private static final String   CLASSLOADERS_ELEMENT = "classloaders";
146 
147     /**
148      * Component to manage "Optional Packages" aka Extensions to allow programs
149      * to declare dependencies on such extensions.
150      */
151     private PackageManager m_packageManager;
152 
153     /**
154      * Parent ClassLoader for all applications aka as the "common" classloader.
155      */
156     private ClassLoader   m_commonClassLoader;
157 
158     /**
159      * The utility class used to verify {@link ClassLoaderMetaData} objects.
160      */
161     private final ClassLoaderVerifier m_verifier = new ClassLoaderVerifier();
162 
163     /**
164      * Utility class to build map of {@link ClassLoader} objects.
165      */
166     private final LoaderBuilder m_builder = new LoaderBuilder();
167 
168     /**
169      * Utility class to read {@link ClassLoaderSetMetaData} objects from XML
170      * trees.
171      */
172     private final ClassLoaderSetReader m_reader = new ClassLoaderSetReader();
173 
174     /**
175      * The map of predefined ClassLoaders. In the current incarnation this only
176      * contains the system classloader.
177      */
178     private Map   m_predefinedLoaders;
179 
180     /**
181      * The contextdata used in interpolation of the policy configuration file.
182      */
183     private final Map   m_data = new HashMap  ();
184 
185     /**
186      * The property expander that will expand properties in the policy
187      * configuraiton file.
188      */
189     private final PropertyExpander m_expander = new PropertyExpander();
190 
191     /**
192      * @dna.dependency type="ExtensionManager"
193      * @dna.dependency type="ClassLoader/common"
194      */
195     public void compose( final ResourceLocator locator )
196         throws MissingResourceException
197     {
198         final ExtensionManager extensionManager = (ExtensionManager) locator.lookup(
199             ExtensionManager.class.getName() );
200         m_packageManager = new PackageManager( extensionManager );
201         m_commonClassLoader = (ClassLoader  ) locator.lookup(
202             ClassLoader  .class.getName() + "/common" );
203     }
204 
205     /**
206      * Setup the map of predefined classloaders.
207      *
208      * @throws Exception if unable to setup map
209      */
210     public void initialize() throws Exception  
211     {
212         m_data.putAll( System.getProperties() );
213 
214         final Map   defined = new HashMap  ();
215         defined.put( "*system*", ClassLoader.getSystemClassLoader() );
216         defined.put( "*common*", m_commonClassLoader );
217         defined.put( "*shared*", m_commonClassLoader );
218         m_predefinedLoaders = Collections.unmodifiableMap( defined );
219     }
220 
221     public void dispose() throws Exception  
222     {
223     }
224 
225     /**
226      * Create a {@link ClassLoader} for a specific application. See Class
227      * Javadoc for description of technique for creating {@link ClassLoader}.
228      *
229      * @param environment   the configuration "environment.xml" for the
230      *                      application
231      * @param homeDirectory the base directory of application
232      * @param workDirectory the work directory of application
233      * @return the ClassLoader created
234      * @throws Exception if an error occurs
235      */
236     public ClassLoaderSet createClassLoaderSet(
237         final Configuration environment,
238         final Map   data,
239         final File   homeDirectory,
240         final File   workDirectory ) throws Exception  
241     {
242         //Configure policy
243         final Configuration policyConfig = environment.getChild( "policy" );
244         final Policy   policy = configurePolicy( policyConfig,
245                                                data,
246                                                homeDirectory,
247                                                workDirectory );
248 
249         final ClassLoaderSetMetaData metaData = getLoaderMetaData( environment );
250 
251         m_verifier.verifyClassLoaderSet( metaData );
252 
253         final LoaderResolver resolver = new SarLoaderResolver(
254             m_packageManager, policy, homeDirectory, workDirectory );
255         setupLogger( resolver );
256         final Map   map = m_builder.buildClassLoaders( metaData,
257                                                      resolver,
258                                                      m_predefinedLoaders );
259         final ClassLoader   defaultClassLoader = (ClassLoader  ) map.get(
260             metaData.getDefault() );
261         return new ClassLoaderSet( defaultClassLoader, map );
262     }
263 
264     /**
265      * Extract the {@link ClassLoaderMetaData} from the environment
266      * configuration. If no &lt;classloader/&gt; section is defined in the
267      * config file then a default metadata will be created.
268      *
269      * @param environment the environment configuration
270      * @return the {@link ClassLoaderMetaData} object
271      */
272     private ClassLoaderSetMetaData getLoaderMetaData(
273         final Configuration environment ) throws Exception  
274     {
275         final boolean loaderDefined = isClassLoaderDefined( environment );
276         if( !loaderDefined )
277         {
278             return createDefaultLoaderMetaData();
279         }
280         else
281         {
282             final Configuration loaderConfig = environment.getChild(
283                 CLASSLOADERS_ELEMENT );
284             final Element   element = ConfigurationUtil.toElement( loaderConfig );
285             return m_reader.build( element );
286         }
287     }
288 
289     /**
290      * Create the default {@link ClassLoaderSetMetaData}. The default metadata
291      * includes all jars in the /SAR-INF/lib/ directory in addition to the
292      * /SAR-INF/classes/ directory.
293      *
294      * @return the default {@link ClassLoaderSetMetaData} object
295      */
296     private ClassLoaderSetMetaData createDefaultLoaderMetaData()
297     {
298         final String  [] includes = new String  []{"SAR-INF/lib/*.jar"};
299         final String  [] excludes = new String  [ 0 ];
300         final FileSetMetaData fileSet = new FileSetMetaData( ".",
301                                                              includes,
302                                                              excludes );
303         final String   name = "default";
304         final String   parent = "*system*";
305         final String  [] entrys = new String  []{"SAR-INF/classes/"};
306         final Extension[] extensions = new Extension[ 0 ];
307         final FileSetMetaData[] filesets = new FileSetMetaData[]{fileSet};
308         final ClassLoaderMetaData loader = new ClassLoaderMetaData( name,
309                                                                     parent,
310                                                                     entrys,
311                                                                     extensions,
312                                                                     filesets );
313         final String  [] predefined = new String  []{parent};
314         final ClassLoaderMetaData[] classLoaders = new ClassLoaderMetaData[]{
315             loader};
316         final JoinMetaData[] joins = new JoinMetaData[ 0 ];
317         return new ClassLoaderSetMetaData( name,
318                                            predefined,
319                                            classLoaders,
320                                            joins );
321     }
322 
323     /**
324      * Return true if environment config defines "classloader" element, false
325      * otherwise.
326      *
327      * @param environment the environment config
328      * @return true if environment config defines "classloader" element, false
329      *         otherwise.
330      */
331     private boolean isClassLoaderDefined( final Configuration environment )
332     {
333         return null != environment.getChild( CLASSLOADERS_ELEMENT, false );
334     }
335 
336     /**
337      * Setup policy based on configuration data.
338      *
339      * @param configuration the configuration data
340      * @param data          the context data used to expand policy file
341      * @param baseDirectory the applications base directory
342      * @throws ConfigurationException if an error occurs
343      */
344     private Policy   configurePolicy( final Configuration configuration,
345                                     final Map   data,
346                                     final File   baseDirectory,
347                                     final File   workDirectory )
348         throws Exception  
349     {
350         final SarPolicyResolver resolver = new SarPolicyResolver(
351             baseDirectory, workDirectory );
352         setupLogger( resolver );
353         final PolicyBuilder builder = new PolicyBuilder();
354         final PolicyReader reader = new PolicyReader();
355         final SarPolicyVerifier verifier = new SarPolicyVerifier();
356         setupLogger( verifier );
357 
358         final Element   element = ConfigurationUtil.toElement( configuration );
359         final HashMap   newData = new HashMap  ();
360         newData.putAll( m_data );
361         newData.putAll( data );
362         newData.put( "/", File.separator );
363 
364         m_expander.expandValues( element, newData );
365 
366         element.setAttribute( "version", "1.0" );
367         try
368         {
369             final PolicyMetaData policy = reader.readPolicy( element );
370             verifier.verifyPolicy( policy );
371             return builder.buildPolicy( policy, resolver );
372         }
373         catch( final Exception   e )
374         {
375             throw new ConfigurationException( e.getMessage(), e );
376         }
377     }
378 }
379
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