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Diffstat (limited to 'qpid/java/systests/src/main/java/org/apache/qpid/util/ClasspathScanner.java')
| -rw-r--r-- | qpid/java/systests/src/main/java/org/apache/qpid/util/ClasspathScanner.java | 234 |
1 files changed, 234 insertions, 0 deletions
diff --git a/qpid/java/systests/src/main/java/org/apache/qpid/util/ClasspathScanner.java b/qpid/java/systests/src/main/java/org/apache/qpid/util/ClasspathScanner.java new file mode 100644 index 0000000000..8cae846a39 --- /dev/null +++ b/qpid/java/systests/src/main/java/org/apache/qpid/util/ClasspathScanner.java @@ -0,0 +1,234 @@ +/* + * + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF licenses this file + * to you under the Apache License, Version 2.0 (the + * "License"); you may not use this file except in compliance + * with the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, + * software distributed under the License is distributed on an + * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY + * KIND, either express or implied. See the License for the + * specific language governing permissions and limitations + * under the License. + * + */ +package org.apache.qpid.util; + +import java.io.File; +import java.util.*; +import java.util.regex.Matcher; +import java.util.regex.Pattern; + +import org.apache.log4j.Logger; + +/** + * An ClasspathScanner scans the classpath for classes that implement an interface or extend a base class and have names + * that match a regular expression. + * + * <p/>In order to test whether a class implements an interface or extends a class, the class must be loaded (unless + * the class files were to be scanned directly). Using this collector can cause problems when it scans the classpath, + * because loading classes will initialize their statics, which in turn may cause undesired side effects. For this + * reason, the collector should always be used with a regular expression, through which the class file names are + * filtered, and only those that pass this filter will be tested. For example, if you define tests in classes that + * end with the keyword "Test" then use the regular expression "Test$" to match this. + * + * <p><table id="crc"><caption>CRC Card</caption> + * <tr><th> Responsibilities <th> Collaborations + * <tr><td> Find all classes matching type and name pattern on the classpath. + * </table> + * + * @todo Add logic to scan jars as well as directories. + */ +public class ClasspathScanner +{ + private static final Logger log = Logger.getLogger(ClasspathScanner.class); + + /** + * Scans the classpath and returns all classes that extend a specified class and match a specified name. + * There is an flag that can be used to indicate that only Java Beans will be matched (that is, only those classes + * that have a default constructor). + * + * @param matchingClass The class or interface to match. + * @param matchingRegexp The regular expression to match against the class name. + * @param beanOnly Flag to indicate that onyl classes with default constructors should be matched. + * + * @return All the classes that match this collector. + */ + public static <T> Collection<Class<? extends T>> getMatches(Class<T> matchingClass, String matchingRegexp, + boolean beanOnly) + { + log.debug("public static <T> Collection<Class<? extends T>> getMatches(Class<T> matchingClass = " + matchingClass + + ", String matchingRegexp = " + matchingRegexp + ", boolean beanOnly = " + beanOnly + "): called"); + + // Build a compiled regular expression from the pattern to match. + Pattern matchPattern = Pattern.compile(matchingRegexp); + + String classPath = System.getProperty("java.class.path"); + Map<String, Class<? extends T>> result = new HashMap<String, Class<? extends T>>(); + + log.debug("classPath = " + classPath); + + // Find matching classes starting from all roots in the classpath. + for (String path : splitClassPath(classPath)) + { + gatherFiles(new File(path), "", result, matchPattern, matchingClass); + } + + return result.values(); + } + + /** + * Finds all matching classes rooted at a given location in the file system. If location is a directory it + * is recursively examined. + * + * @param classRoot The root of the current point in the file system being examined. + * @param classFileName The name of the current file or directory to examine. + * @param result The accumulated mapping from class names to classes that match the scan. + * + * @todo Recursion ok as file system depth is not likely to exhaust the stack. Might be better to replace with + * iteration. + */ + private static <T> void gatherFiles(File classRoot, String classFileName, Map<String, Class<? extends T>> result, + Pattern matchPattern, Class<? extends T> matchClass) + { + log.debug("private static <T> void gatherFiles(File classRoot = " + classRoot + ", String classFileName = " + + classFileName + ", Map<String, Class<? extends T>> result, Pattern matchPattern = " + matchPattern + + ", Class<? extends T> matchClass = " + matchClass + "): called"); + + File thisRoot = new File(classRoot, classFileName); + + // If the current location is a file, check if it is a matching class. + if (thisRoot.isFile()) + { + // Check that the file has a matching name. + if (matchesName(thisRoot.getName(), matchPattern)) + { + String className = classNameFromFile(thisRoot.getName()); + + // Check that the class has matching type. + try + { + Class<?> candidateClass = Class.forName(className); + + Class matchedClass = matchesClass(candidateClass, matchClass); + + if (matchedClass != null) + { + result.put(className, matchedClass); + } + } + catch (ClassNotFoundException e) + { + // Ignore this. The matching class could not be loaded. + log.debug("Got ClassNotFoundException, ignoring.", e); + } + } + + return; + } + // Otherwise the current location is a directory, so examine all of its contents. + else + { + String[] contents = thisRoot.list(); + + if (contents != null) + { + for (String content : contents) + { + gatherFiles(classRoot, classFileName + File.separatorChar + content, result, matchPattern, matchClass); + } + } + } + } + + /** + * Checks if the specified class file name corresponds to a class with name matching the specified regular expression. + * + * @param classFileName The class file name. + * @param matchPattern The regular expression pattern to match. + * + * @return <tt>true</tt> if the class name matches, <tt>false</tt> otherwise. + */ + private static boolean matchesName(String classFileName, Pattern matchPattern) + { + String className = classNameFromFile(classFileName); + Matcher matcher = matchPattern.matcher(className); + + return matcher.matches(); + } + + /** + * Checks if the specified class to compare extends the base class being scanned for. + * + * @param matchingClass The base class to match against. + * @param toMatch The class to match against the base class. + * + * @return The class to check, cast as an instance of the class to match if the class extends the base class, or + * <tt>null</tt> otherwise. + */ + private static <T> Class<? extends T> matchesClass(Class<?> matchingClass, Class<? extends T> toMatch) + { + try + { + return matchingClass.asSubclass(toMatch); + } + catch (ClassCastException e) + { + return null; + } + } + + /** + * Takes a classpath (which is a series of paths) and splits it into its component paths. + * + * @param classPath The classpath to split. + * + * @return A list of the component paths that make up the class path. + */ + private static List<String> splitClassPath(String classPath) + { + List<String> result = new LinkedList<String>(); + String separator = System.getProperty("path.separator"); + StringTokenizer tokenizer = new StringTokenizer(classPath, separator); + + while (tokenizer.hasMoreTokens()) + { + result.add(tokenizer.nextToken()); + } + + return result; + } + + /** + * Translates from the filename of a class to its fully qualified classname. Files are named using forward slash + * seperators and end in ".class", whereas fully qualified class names use "." sperators and no ".class" ending. + * + * @param classFileName The filename of the class to translate to a class name. + * + * @return The fully qualified class name. + */ + private static String classNameFromFile(String classFileName) + { + log.debug("private static String classNameFromFile(String classFileName = " + classFileName + "): called"); + + // Remove the .class ending. + String s = classFileName.substring(0, classFileName.length() - ".class".length()); + + // Turn / seperators in . seperators. + String s2 = s.replace(File.separatorChar, '.'); + + // Knock off any leading . caused by a leading /. + if (s2.startsWith(".")) + { + return s2.substring(1); + } + + return s2; + } +} |