Source Code Cross Referenced for ComponentInstantiatorSourceImpl.java in  » Library » Tapestry » org » apache » tapestry » internal » services » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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Java Source Code / Java Documentation » Library » Tapestry » org.apache.tapestry.internal.services 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


001:        // Copyright 2006, 2007 The Apache Software Foundation
002:        //
003:        // Licensed under the Apache License, Version 2.0 (the "License");
004:        // you may not use this file except in compliance with the License.
005:        // You may obtain a copy of the License at
006:        //
007:        //     http://www.apache.org/licenses/LICENSE-2.0
008:        //
009:        // Unless required by applicable law or agreed to in writing, software
010:        // distributed under the License is distributed on an "AS IS" BASIS,
011:        // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
012:        // See the License for the specific language governing permissions and
013:        // limitations under the License.
014:
015:        package org.apache.tapestry.internal.services;
016:
017:        import static org.apache.tapestry.ioc.internal.util.CollectionFactory.newMap;
018:        import static org.apache.tapestry.ioc.internal.util.CollectionFactory.newSet;
019:
020:        import java.net.URL;
021:        import java.util.Map;
022:        import java.util.Set;
023:
024:        import javassist.CannotCompileException;
025:        import javassist.ClassPath;
026:        import javassist.ClassPool;
027:        import javassist.CtClass;
028:        import javassist.Loader;
029:        import javassist.LoaderClassPath;
030:        import javassist.NotFoundException;
031:        import javassist.Translator;
032:
033:        import org.apache.commons.logging.Log;
034:        import org.apache.tapestry.internal.event.InvalidationEventHubImpl;
035:        import org.apache.tapestry.internal.events.UpdateListener;
036:        import org.apache.tapestry.internal.util.URLChangeTracker;
037:        import org.apache.tapestry.ioc.internal.services.ClassFactoryClassPool;
038:        import org.apache.tapestry.ioc.internal.services.ClassFactoryImpl;
039:        import org.apache.tapestry.ioc.internal.util.Defense;
040:        import org.apache.tapestry.ioc.services.ClassFactory;
041:
042:        /**
043:         * A wrapper around a Javassist class loader that allows certain classes to be modified as they are
044:         * loaded.
045:         */
046:        public final class ComponentInstantiatorSourceImpl extends
047:                InvalidationEventHubImpl implements  Translator,
048:                ComponentInstantiatorSource, UpdateListener {
049:            /**
050:             * Add -Djavassist-write-dir=target/transformed-classes to the command line to force output of
051:             * transformed classes to disk (for hardcore debugging).
052:             */
053:            private static final String JAVASSIST_WRITE_DIR = System
054:                    .getProperty("javassist-write-dir");
055:
056:            private final Set<String> _controlledPackageNames = newSet();
057:
058:            private final URLChangeTracker _changeTracker = new URLChangeTracker();
059:
060:            private final ClassLoader _parent;
061:
062:            private ClassFactoryClassPool _classPool;
063:
064:            private Loader _loader;
065:
066:            private final ComponentClassTransformer _transformer;
067:
068:            private final Log _log;
069:
070:            private ClassFactory _classFactory;
071:
072:            /** Map from class name to Instantiator. */
073:            private final Map<String, Instantiator> _instantiatorMap = newMap();
074:
075:            private class PackageAwareLoader extends Loader {
076:                public PackageAwareLoader(ClassLoader parent,
077:                        ClassPool classPool) {
078:                    super (parent, classPool);
079:                }
080:
081:                @Override
082:                protected Class findClass(String className)
083:                        throws ClassNotFoundException {
084:                    if (inControlledPackage(className))
085:                        return super .findClass(className);
086:
087:                    // Returning null forces delegation to the parent class loader.
088:
089:                    return null;
090:                }
091:
092:            }
093:
094:            public ComponentInstantiatorSourceImpl(ClassLoader parent,
095:                    ComponentClassTransformer transformer, Log log) {
096:                _parent = parent;
097:                _transformer = transformer;
098:                _log = log;
099:
100:                initializeService();
101:            }
102:
103:            public synchronized void checkForUpdates() {
104:                if (!_changeTracker.containsChanges())
105:                    return;
106:
107:                _changeTracker.clear();
108:                _instantiatorMap.clear();
109:
110:                // Release the existing class pool, loader and so forth.
111:                // Create a new one.
112:
113:                initializeService();
114:
115:                // Tell everyone that the world has changed and they should discard
116:                // their cache.
117:
118:                fireInvalidationEvent();
119:            }
120:
121:            /**
122:             * Invoked at object creation, or when there are updates to class files (i.e., invalidation), to
123:             * create a new set of Javassist class pools and loaders.
124:             */
125:            private void initializeService() {
126:                _classPool = new ClassFactoryClassPool(_parent);
127:
128:                _loader = new PackageAwareLoader(_parent, _classPool);
129:
130:                ClassPath path = new LoaderClassPath(_loader);
131:
132:                _classPool.appendClassPath(path);
133:
134:                try {
135:                    _loader.addTranslator(_classPool, this );
136:                } catch (Exception ex) {
137:                    throw new RuntimeException(ex);
138:                }
139:
140:                _classFactory = new ClassFactoryImpl(_loader, _classPool, _log);
141:            }
142:
143:            // This is called from well within a synchronized block.
144:            public void onLoad(ClassPool pool, String classname)
145:                    throws NotFoundException, CannotCompileException {
146:                _log.debug("BEGIN onLoad " + classname);
147:
148:                // This is our chance to make changes to the CtClass before it is loaded into memory.
149:
150:                String diag = "FAIL";
151:
152:                // If we are loading a class, it is because it is in a controlled package. There may be
153:                // errors in the class that keep it from loading. By adding it to the change tracker
154:                // early, we ensure that when the class is fixed, the change is picked up. Originally,
155:                // this code was at the end of the method, and classes that contained errors would not be
156:                // reloaded even after the code was fixed.
157:
158:                addClassFileToChangeTracker(classname);
159:
160:                try {
161:                    CtClass ctClass = pool.get(classname);
162:
163:                    // Force the creation of the super-class before the target class.
164:
165:                    forceSuperclassTransform(ctClass);
166:
167:                    // Do the transformations here
168:
169:                    _transformer.transformComponentClass(ctClass, _loader);
170:
171:                    writeClassToFileSystemForHardCoreDebuggingPurposesOnly(ctClass);
172:
173:                    diag = "END";
174:                } catch (ClassNotFoundException ex) {
175:                    throw new CannotCompileException(ex);
176:                } finally {
177:                    _log.debug(String.format("%5s onLoad %s", diag, classname));
178:                }
179:            }
180:
181:            private void writeClassToFileSystemForHardCoreDebuggingPurposesOnly(
182:                    CtClass ctClass) {
183:                if (JAVASSIST_WRITE_DIR == null)
184:                    return;
185:
186:                try {
187:                    boolean p = ctClass.stopPruning(true);
188:                    ctClass.writeFile(JAVASSIST_WRITE_DIR);
189:                    ctClass.defrost();
190:                    ctClass.stopPruning(p);
191:
192:                } catch (Exception ex) {
193:                    throw new RuntimeException(ex);
194:                }
195:            }
196:
197:            private void addClassFileToChangeTracker(String classname) {
198:                String path = classname.replace('.', '/') + ".class";
199:
200:                URL url = _loader.getResource(path);
201:
202:                _changeTracker.add(url);
203:            }
204:
205:            private void forceSuperclassTransform(CtClass ctClass)
206:                    throws NotFoundException, ClassNotFoundException {
207:                CtClass super Class = ctClass.getSuperclass();
208:
209:                findClass(super Class.getName());
210:            }
211:
212:            /** Does nothing. */
213:            public void start(ClassPool pool) throws NotFoundException,
214:                    CannotCompileException {
215:            }
216:
217:            public synchronized Instantiator findInstantiator(String classname) {
218:                Instantiator result = _instantiatorMap.get(classname);
219:
220:                if (result == null) {
221:                    Class instanceClass = findClass(classname);
222:
223:                    result = _transformer.createInstantiator(instanceClass);
224:
225:                    _instantiatorMap.put(classname, result);
226:                }
227:
228:                return result;
229:            }
230:
231:            private Class findClass(String classname) {
232:                try {
233:                    return _loader.loadClass(classname);
234:                } catch (ClassNotFoundException ex) {
235:                    throw new RuntimeException(ex);
236:                }
237:            }
238:
239:            /**
240:             * Returns true if the package for the class name is in a package that is controlled by the
241:             * enhancer. Controlled packages are identified by {@link #addPackage(String)}.
242:             */
243:
244:            boolean inControlledPackage(String classname) {
245:                String packageName = stripTail(classname);
246:
247:                while (packageName != null) {
248:                    if (_controlledPackageNames.contains(packageName))
249:                        return true;
250:
251:                    packageName = stripTail(packageName);
252:                }
253:
254:                return false;
255:            }
256:
257:            private String stripTail(String input) {
258:                int lastdot = input.lastIndexOf('.');
259:
260:                if (lastdot < 0)
261:                    return null;
262:
263:                return input.substring(0, lastdot);
264:            }
265:
266:            // synchronized may be overkill, but that's ok.
267:            public synchronized void addPackage(String packageName) {
268:                Defense.notBlank(packageName, "packageName");
269:
270:                // TODO: Should we check that packages are not nested?
271:
272:                _controlledPackageNames.add(packageName);
273:            }
274:
275:            public boolean exists(String className) {
276:                String path = className.replace(".", "/") + ".class";
277:
278:                return _parent.getResource(path) != null;
279:            }
280:
281:            public ClassFactory getClassFactory() {
282:                return _classFactory;
283:            }
284:        }
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