Source Code Cross Referenced for ClasspathUtils.java in  » Build » ANT » org » apache » tools » ant » util » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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Java Source Code / Java Documentation » Build » ANT » org.apache.tools.ant.util 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


001:        /*
002:         *  Licensed to the Apache Software Foundation (ASF) under one or more
003:         *  contributor license agreements.  See the NOTICE file distributed with
004:         *  this work for additional information regarding copyright ownership.
005:         *  The ASF licenses this file to You under the Apache License, Version 2.0
006:         *  (the "License"); you may not use this file except in compliance with
007:         *  the License.  You may obtain a copy of the License at
008:         *
009:         *      http://www.apache.org/licenses/LICENSE-2.0
010:         *
011:         *  Unless required by applicable law or agreed to in writing, software
012:         *  distributed under the License is distributed on an "AS IS" BASIS,
013:         *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014:         *  See the License for the specific language governing permissions and
015:         *  limitations under the License.
016:         *
017:         */
018:        package org.apache.tools.ant.util;
019:
020:        import org.apache.tools.ant.AntClassLoader;
021:        import org.apache.tools.ant.BuildException;
022:        import org.apache.tools.ant.Project;
023:        import org.apache.tools.ant.ProjectComponent;
024:        import org.apache.tools.ant.MagicNames;
025:        import org.apache.tools.ant.types.Path;
026:        import org.apache.tools.ant.types.Reference;
027:
028:        // CheckStyle:HideUtilityClassConstructorCheck OFF - bc
029:
030:        /**
031:         * Offers some helper methods on the Path structure in ant.
032:         *
033:         * <p>The basic idea behind this utility class is to use it from inside the
034:         * different Ant objects (and user defined objects) that need classLoading
035:         * for their operation.
036:         * Normally those would have a setClasspathRef() {for the @classpathref}
037:         * and/or a createClasspath() {for the nested &lt;classpath&gt;}
038:         * Typically one would have in your Ant Task or DataType</p>
039:         *
040:         * <pre><code>
041:         * ClasspathUtils.Delegate cpDelegate;
042:         *
043:         * public void init() {
044:         *     this.cpDelegate = ClasspathUtils.getDelegate(this);
045:         *     super.init();
046:         * }
047:         *
048:         * public void setClasspathRef(Reference r) {
049:         *     this.cpDelegate.setClasspathRef(r);
050:         * }
051:         *
052:         * public Path createClasspath() {
053:         *     return this.cpDelegate.createClasspath();
054:         * }
055:         *
056:         * public void setClassname(String fqcn) {
057:         *     this.cpDelegate.setClassname(fqcn);
058:         * }
059:         * </code></pre>
060:         *
061:         * <p>At execution time, when you actually need the classloading
062:         * you can just:</p>
063:         *
064:         * <pre><code>
065:         *     Object o = this.cpDelegate.newInstance();
066:         * </code></pre>
067:         *
068:         * @since Ant 1.6
069:         */
070:        public class ClasspathUtils {
071:
072:            /**
073:             * Name of the magic property that controls classloader reuse in Ant 1.4.
074:             */
075:            public static final String REUSE_LOADER_REF = MagicNames.REFID_CLASSPATH_REUSE_LOADER;
076:
077:            /**
078:             * Convenience overloaded version of {@link
079:             * #getClassLoaderForPath(Project, Reference, boolean)}.
080:             *
081:             * <p>Assumes the logical 'false' for the reverseLoader.</p>
082:             *
083:             * @param p the project
084:             * @param ref the reference
085:             * @return The class loader
086:             */
087:            public static ClassLoader getClassLoaderForPath(Project p,
088:                    Reference ref) {
089:
090:                return getClassLoaderForPath(p, ref, false);
091:            }
092:
093:            /**
094:             * Convenience overloaded version of {@link #getClassLoaderForPath(Project, Path,
095:             * String, boolean)}.
096:             *
097:             * <p>Delegates to the other one after extracting the referenced
098:             * Path from the Project. This checks also that the passed
099:             * Reference is pointing to a Path all right.</p>
100:             * @param p current Ant project
101:             * @param ref Reference to Path structure
102:             * @param reverseLoader if set to true this new loader will take
103:             * precedence over its parent (which is contra the regular
104:             * classloader behaviour)
105:             * @return The class loader
106:             */
107:            public static ClassLoader getClassLoaderForPath(Project p,
108:                    Reference ref, boolean reverseLoader) {
109:
110:                String pathId = ref.getRefId();
111:                Object path = p.getReference(pathId);
112:                if (!(path instanceof  Path)) {
113:                    throw new BuildException("The specified classpathref "
114:                            + pathId + " does not reference a Path.");
115:                }
116:                String loaderId = MagicNames.REFID_CLASSPATH_LOADER_PREFIX
117:                        + pathId;
118:                return getClassLoaderForPath(p, (Path) path, loaderId,
119:                        reverseLoader);
120:            }
121:
122:            /**
123:             * Convenience overloaded version of {@link
124:             * #getClassLoaderForPath(Project, Path, String, boolean)}.
125:             *
126:             * <p>Assumes the logical 'false' for the reverseLoader.</p>
127:             *
128:             * @param p current Ant project
129:             * @param path the path
130:             * @param loaderId the loader id string
131:             * @return The class loader
132:             */
133:            public static ClassLoader getClassLoaderForPath(Project p,
134:                    Path path, String loaderId) {
135:
136:                return getClassLoaderForPath(p, path, loaderId, false);
137:            }
138:
139:            /**
140:             * Convenience overloaded version of {@link
141:             * #getClassLoaderForPath(Project, Path, String, boolean, boolean)}.
142:             *
143:             * <p>Sets value for 'reuseLoader' to true if the magic property
144:             * has been set.</p>
145:             *
146:             * @param p the project
147:             * @param path the path
148:             * @param loaderId the loader id string
149:             * @param reverseLoader if set to true this new loader will take
150:             * precedence over its parent (which is contra the regular
151:             * classloader behaviour)
152:             * @return The class loader
153:             */
154:            public static ClassLoader getClassLoaderForPath(Project p,
155:                    Path path, String loaderId, boolean reverseLoader) {
156:                return getClassLoaderForPath(p, path, loaderId, reverseLoader,
157:                        isMagicPropertySet(p));
158:            }
159:
160:            /**
161:             * Gets a classloader that loads classes from the classpath
162:             * defined in the path argument.
163:             *
164:             * <p>Based on the setting of the magic property
165:             * 'ant.reuse.loader' this will try to reuse the previously
166:             * created loader with that id, and of course store it there upon
167:             * creation.</p>
168:             * @param p             Ant Project where the handled components are living in.
169:             * @param path          Path object to be used as classpath for this classloader
170:             * @param loaderId      identification for this Loader,
171:             * @param reverseLoader if set to true this new loader will take
172:             *                      precedence over its parent (which is contra the regular
173:             *                      classloader behaviour)
174:             * @param reuseLoader   if true reuse the loader if it is found
175:             * @return              ClassLoader that uses the Path as its classpath.
176:             */
177:            public static ClassLoader getClassLoaderForPath(Project p,
178:                    Path path, String loaderId, boolean reverseLoader,
179:                    boolean reuseLoader) {
180:
181:                ClassLoader cl = null;
182:
183:                // magic property
184:                if (loaderId != null && reuseLoader) {
185:                    Object reusedLoader = p.getReference(loaderId);
186:                    if (reusedLoader != null
187:                            && !(reusedLoader instanceof  ClassLoader)) {
188:                        throw new BuildException("The specified loader id "
189:                                + loaderId
190:                                + " does not reference a class loader");
191:                    }
192:                    cl = (ClassLoader) reusedLoader;
193:                }
194:                if (cl == null) {
195:                    cl = getUniqueClassLoaderForPath(p, path, reverseLoader);
196:                    if (loaderId != null && reuseLoader) {
197:                        p.addReference(loaderId, cl);
198:                    }
199:                }
200:                return cl;
201:            }
202:
203:            /**
204:             * Gets a fresh, different, previously unused classloader that uses the
205:             * passed path as its classpath.
206:             *
207:             * <p>This method completely ignores the ant.reuse.loader magic
208:             * property and should be used with caution.</p>
209:             * @param p             Ant Project where the handled components are living in.
210:             * @param path          the classpath for this loader
211:             * @param reverseLoader if set to true this new loader will take
212:             *                      precedence over its parent (which is contra the regular
213:             *                      classloader behaviour)
214:             * @return The fresh, different, previously unused class loader.
215:             */
216:            public static ClassLoader getUniqueClassLoaderForPath(Project p,
217:                    Path path, boolean reverseLoader) {
218:                AntClassLoader acl = p.createClassLoader(path);
219:                if (reverseLoader) {
220:                    acl.setParentFirst(false);
221:                    acl.addJavaLibraries();
222:                }
223:                return acl;
224:            }
225:
226:            /**
227:             * Creates a fresh object instance of the specified classname.
228:             *
229:             * <p> This uses the userDefinedLoader to load the specified class,
230:             * and then makes an instance using the default no-argument constructor.
231:             * </p>
232:             *
233:             * @param className the full qualified class name to load.
234:             * @param userDefinedLoader the classloader to use.
235:             * @return The fresh object instance
236:             * @throws BuildException when loading or instantiation failed.
237:             */
238:            public static Object newInstance(String className,
239:                    ClassLoader userDefinedLoader) {
240:                return newInstance(className, userDefinedLoader, Object.class);
241:            }
242:
243:            /**
244:             * Creates a fresh object instance of the specified classname.
245:             *
246:             * <p> This uses the userDefinedLoader to load the specified class,
247:             * and then makes an instance using the default no-argument constructor.
248:             * </p>
249:             *
250:             * @param className the full qualified class name to load.
251:             * @param userDefinedLoader the classloader to use.
252:             * @param expectedType the Class that the result should be assignment
253:             * compatible with. (No ClassCastException will be thrown in case
254:             * the result of this method is casted to the expectedType)
255:             * @return The fresh object instance
256:             * @throws BuildException when loading or instantiation failed.
257:             * @since Ant 1.7
258:             */
259:            public static Object newInstance(String className,
260:                    ClassLoader userDefinedLoader, Class expectedType) {
261:                try {
262:                    Class clazz = Class.forName(className, true,
263:                            userDefinedLoader);
264:                    Object o = clazz.newInstance();
265:                    if (!expectedType.isInstance(o)) {
266:                        throw new BuildException("Class of unexpected Type: "
267:                                + className + " expected :" + expectedType);
268:                    }
269:                    return o;
270:                } catch (ClassNotFoundException e) {
271:                    throw new BuildException("Class not found: " + className, e);
272:                } catch (InstantiationException e) {
273:                    throw new BuildException("Could not instantiate "
274:                            + className + ". Specified class should have a no "
275:                            + "argument constructor.", e);
276:                } catch (IllegalAccessException e) {
277:                    throw new BuildException("Could not instantiate "
278:                            + className + ". Specified class should have a "
279:                            + "public constructor.", e);
280:                } catch (LinkageError e) {
281:                    throw new BuildException(
282:                            "Class "
283:                                    + className
284:                                    + " could not be loaded because of an invalid dependency.",
285:                            e);
286:                }
287:            }
288:
289:            /**
290:             * Obtains a delegate that helps out with classic classpath configuration.
291:             *
292:             * @param component your projectComponent that needs the assistence
293:             * @return the helper, delegate.
294:             * @see ClasspathUtils.Delegate
295:             */
296:            public static Delegate getDelegate(ProjectComponent component) {
297:                return new Delegate(component);
298:            }
299:
300:            /**
301:             * Checks for the magic property that enables class loader reuse
302:             * for <taskdef> and <typedef> in Ant 1.5 and earlier.
303:             */
304:            private static boolean isMagicPropertySet(Project p) {
305:                return p.getProperty(REUSE_LOADER_REF) != null;
306:            }
307:
308:            /**
309:             * Delegate that helps out any specific ProjectComponent that needs
310:             * dynamic classloading.
311:             *
312:             * <p>Ant ProjectComponents that need a to be able to dynamically load
313:             * Classes and instantiate them often expose the following ant syntax
314:             * sugar: </p>
315:             *
316:             * <ul><li> nested &lt;classpath&gt; </li>
317:             * <li> attribute @classpathref </li>
318:             * <li> attribute @classname </li></ul>
319:             *
320:             * <p> This class functions as a delegate handling the configuration
321:             * issues for this recurring pattern.  Its usage pattern, as the name
322:             * suggests, is delegation rather than inheritance. </p>
323:             *
324:             * @since Ant 1.6
325:             */
326:            public static class Delegate {
327:                private final ProjectComponent component;
328:                private Path classpath;
329:                private String classpathId;
330:                private String className;
331:                private String loaderId;
332:                private boolean reverseLoader = false;
333:
334:                /**
335:                 * Construct a Delegate
336:                 * @param component the ProjectComponent this delegate is for.
337:                 */
338:                Delegate(ProjectComponent component) {
339:                    this .component = component;
340:                }
341:
342:                /**
343:                 * This method is a Delegate method handling the @classpath attribute.
344:                 *
345:                 * <p>This attribute can set a path to add to the classpath.</p>
346:                 *
347:                 * @param classpath the path to use for the classpath.
348:                 */
349:                public void setClasspath(Path classpath) {
350:                    if (this .classpath == null) {
351:                        this .classpath = classpath;
352:                    } else {
353:                        this .classpath.append(classpath);
354:                    }
355:                }
356:
357:                /**
358:                 * Delegate method handling the &lt;classpath&gt; tag.
359:                 *
360:                 * <p>This nested path-like structure can set a path to add to the
361:                 * classpath.</p>
362:                 *
363:                 * @return the created path.
364:                 */
365:                public Path createClasspath() {
366:                    if (this .classpath == null) {
367:                        this .classpath = new Path(component.getProject());
368:                    }
369:                    return this .classpath.createPath();
370:                }
371:
372:                /**
373:                 * Delegate method handling the @classname attribute.
374:                 *
375:                 * <p>This attribute sets the full qualified class name of the class
376:                 * to load and instantiate.</p>
377:                 *
378:                 * @param fcqn the name of the class to load.
379:                 */
380:                public void setClassname(String fcqn) {
381:                    this .className = fcqn;
382:                }
383:
384:                /**
385:                 * Delegate method handling the @classpathref attribute.
386:                 *
387:                 * <p>This attribute can add a referenced path-like structure to the
388:                 * classpath.</p>
389:                 *
390:                 * @param r the reference to the classpath.
391:                 */
392:                public void setClasspathref(Reference r) {
393:                    this .classpathId = r.getRefId();
394:                    createClasspath().setRefid(r);
395:                }
396:
397:                /**
398:                 * Delegate method handling the @reverseLoader attribute.
399:                 *
400:                 * <p>This attribute can set a boolean indicating that the used
401:                 * classloader should NOT follow the classical parent-first scheme.
402:                 * </p>
403:                 *
404:                 * <p>By default this is supposed to be false.</p>
405:                 *
406:                 * <p>Caution: this behaviour is contradictory to the normal way
407:                 * classloaders work.  Do not let your ProjectComponent use it if
408:                 * you are not really sure.</p>
409:                 *
410:                 * @param reverseLoader if true reverse the order of looking up a class.
411:                 */
412:                public void setReverseLoader(boolean reverseLoader) {
413:                    this .reverseLoader = reverseLoader;
414:                }
415:
416:                /**
417:                 * Sets the loaderRef.
418:                 * @param r the reference to the loader.
419:                 */
420:                public void setLoaderRef(Reference r) {
421:                    this .loaderId = r.getRefId();
422:                }
423:
424:                /**
425:                 * Finds or creates the classloader for this object.
426:                 * @return The class loader.
427:                 */
428:                public ClassLoader getClassLoader() {
429:                    return getClassLoaderForPath(getContextProject(),
430:                            this .classpath, getClassLoadId(),
431:                            this .reverseLoader, loaderId != null
432:                                    || isMagicPropertySet(getContextProject()));
433:                }
434:
435:                /**
436:                 * The project of the ProjectComponent we are working for.
437:                 */
438:                private Project getContextProject() {
439:                    return this .component.getProject();
440:                }
441:
442:                /**
443:                 * Computes the loaderId based on the configuration of the component.
444:                 * @return a loader identifier.
445:                 */
446:                public String getClassLoadId() {
447:                    return this .loaderId == null && this .classpathId != null ? MagicNames.REFID_CLASSPATH_LOADER_PREFIX
448:                            + this .classpathId
449:                            : this .loaderId;
450:                }
451:
452:                /**
453:                 * Helper method obtaining a fresh instance of the class specified
454:                 * in the @classname and using the specified classpath.
455:                 *
456:                 * @return the fresh instantiated object.
457:                 */
458:                public Object newInstance() {
459:                    return ClasspathUtils.newInstance(this .className,
460:                            getClassLoader());
461:                }
462:
463:                /**
464:                 * The classpath.
465:                 * @return the classpath.
466:                 */
467:                public Path getClasspath() {
468:                    return classpath;
469:                }
470:
471:                /**
472:                 * Get the reverseLoader setting.
473:                 * @return true if looking up in reverse order.
474:                 */
475:                public boolean isReverseLoader() {
476:                    return reverseLoader;
477:                }
478:
479:                //TODO no methods yet for getClassname
480:                //TODO no method for newInstance using a reverse-classloader
481:            }
482:        }
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