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XWork is an command-pattern framework that is used to power WebWork
as well as other applications. XWork provides an Inversion of Control
container, a powerful expression language, data type conversion,
validation, and pluggable configuration.
/* Copyright 2005-2006 Tim Fennell
*
* Licensed 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 com.opensymphony.xwork2.util;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.lang.annotation.Annotation;
import java.net.URL;
import java.net.URLDecoder;
import java.util.Enumeration;
import java.util.HashSet;
import java.util.Set;
import java.util.jar.JarEntry;
import java.util.jar.JarInputStream;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
/**
* ResolverUtil is used to locate classes that are available in the/a class path and meet
* arbitrary conditions. The two most common conditions are that a class implements/extends
* another class, or that is it annotated with a specific annotation. However, through the use
* of the {@link Test} class it is possible to search using arbitrary conditions.
*
* A ClassLoader is used to locate all locations (directories and jar files) in the class
* path that contain classes within certain packages, and then to load those classes and
* check them. By default the ClassLoader returned by
* {@code Thread.currentThread().getContextClassLoader()} is used, but this can be overridden
* by calling {@link #setClassLoader(ClassLoader)} prior to invoking any of the {@code find()}
* methods.
*
* General searches are initiated by calling the
* {@link #find(com.opensymphony.xwork2.util.ResolverUtil.Test, String...)} ()} method and supplying
* a package name and a Test instance. This will cause the named package and all sub-packages
* to be scanned for classes that meet the test. There are also utility methods for the common
* use cases of scanning multiple packages for extensions of particular classes, or classes
* annotated with a specific annotation.
*
* The standard usage pattern for the ResolverUtil class is as follows:
*
*
*ResolverUtil<ActionBean> resolver = new ResolverUtil<ActionBean>();
*resolver.findImplementation(ActionBean.class, pkg1, pkg2);
*resolver.find(new CustomTest(), pkg1);
*resolver.find(new CustomTest(), pkg2);
*Collection<ActionBean> beans = resolver.getClasses();
*
*
* This class was copied from Stripes - http://stripes.mc4j.org/confluence/display/stripes/Home
*
*
* @author Tim Fennell
*/
public class ResolverUtil {
/** An instance of Log to use for logging in this class. */
private static final Log log = LogFactory.getLog(ResolverUtil.class);
/**
* A simple interface that specifies how to test classes to determine if they
* are to be included in the results produced by the ResolverUtil.
*/
public static interface Test {
/**
* Will be called repeatedly with candidate classes. Must return True if a class
* is to be included in the results, false otherwise.
*/
boolean matches(Class type);
}
/**
* A Test that checks to see if each class is assignable to the provided class. Note
* that this test will match the parent type itself if it is presented for matching.
*/
public static class IsA implements Test {
private Class parent;
/** Constructs an IsA test using the supplied Class as the parent class/interface. */
public IsA(Class parentType) { this.parent = parentType; }
/** Returns true if type is assignable to the parent type supplied in the constructor. */
public boolean matches(Class type) {
return type != null && parent.isAssignableFrom(type);
}
@Override public String toString() {
return "is assignable to " + parent.getSimpleName();
}
}
/**
* A Test that checks to see if each class name ends with the provided suffix.
*/
public static class NameEndsWith implements Test {
private String suffix;
/** Constructs a NameEndsWith test using the supplied suffix. */
public NameEndsWith(String suffix) { this.suffix = suffix; }
/** Returns true if type name ends with the suffix supplied in the constructor. */
public boolean matches(Class type) {
return type != null && type.getName().endsWith(suffix);
}
@Override public String toString() {
return "ends with the suffix " + suffix;
}
}
/**
* A Test that checks to see if each class is annotated with a specific annotation. If it
* is, then the test returns true, otherwise false.
*/
public static class AnnotatedWith implements Test {
private Class annotation;
/** Construts an AnnotatedWith test for the specified annotation type. */
public AnnotatedWith(Class annotation) { this.annotation = annotation; }
/** Returns true if the type is annotated with the class provided to the constructor. */
public boolean matches(Class type) {
return type != null && type.isAnnotationPresent(annotation);
}
@Override public String toString() {
return "annotated with @" + annotation.getSimpleName();
}
}
/** The set of matches being accumulated. */
private Set> matches = new HashSet>();
/**
* The ClassLoader to use when looking for classes. If null then the ClassLoader returned
* by Thread.currentThread().getContextClassLoader() will be used.
*/
private ClassLoader classloader;
/**
* Provides access to the classes discovered so far. If no calls have been made to
* any of the {@code find()} methods, this set will be empty.
*
* @return the set of classes that have been discovered.
*/
public Set> getClasses() {
return matches;
}
/**
* Returns the classloader that will be used for scanning for classes. If no explicit
* ClassLoader has been set by the calling, the context class loader will be used.
*
* @return the ClassLoader that will be used to scan for classes
*/
public ClassLoader getClassLoader() {
return classloader == null ? Thread.currentThread().getContextClassLoader() : classloader;
}
/**
* Sets an explicit ClassLoader that should be used when scanning for classes. If none
* is set then the context classloader will be used.
*
* @param classloader a ClassLoader to use when scanning for classes
*/
public void setClassLoader(ClassLoader classloader) { this.classloader = classloader; }
/**
* Attempts to discover classes that are assignable to the type provided. In the case
* that an interface is provided this method will collect implementations. In the case
* of a non-interface class, subclasses will be collected. Accumulated classes can be
* accessed by calling {@link #getClasses()}.
*
* @param parent the class of interface to find subclasses or implementations of
* @param packageNames one or more package names to scan (including subpackages) for classes
*/
public void findImplementations(Class parent, String... packageNames) {
if (packageNames == null) return;
Test test = new IsA(parent);
for (String pkg : packageNames) {
findInPackage(test, pkg);
}
}
/**
* Attempts to discover classes who's name ends with the provided suffix. Accumulated classes can be
* accessed by calling {@link #getClasses()}.
*
* @param suffix The class name suffix to match
* @param packageNames one or more package names to scan (including subpackages) for classes
*/
public void findSuffix(String suffix, String... packageNames) {
if (packageNames == null) return;
Test test = new NameEndsWith(suffix);
for (String pkg : packageNames) {
findInPackage(test, pkg);
}
}
/**
* Attempts to discover classes that are annotated with to the annotation. Accumulated
* classes can be accessed by calling {@link #getClasses()}.
*
* @param annotation the annotation that should be present on matching classes
* @param packageNames one or more package names to scan (including subpackages) for classes
*/
public void findAnnotated(Class annotation, String... packageNames) {
if (packageNames == null) return;
Test test = new AnnotatedWith(annotation);
for (String pkg : packageNames) {
findInPackage(test, pkg);
}
}
/**
* Attempts to discover classes that pass the test. Accumulated
* classes can be accessed by calling {@link #getClasses()}.
*
* @param test the test to determine matching classes
* @param packageNames one or more package names to scan (including subpackages) for classes
*/
public void find(Test test, String... packageNames) {
if (packageNames == null) return;
for (String pkg : packageNames) {
findInPackage(test, pkg);
}
}
/**
* Scans for classes starting at the package provided and descending into subpackages.
* Each class is offered up to the Test as it is discovered, and if the Test returns
* true the class is retained. Accumulated classes can be fetched by calling
* {@link #getClasses()}.
*
* @param test an instance of {@link Test} that will be used to filter classes
* @param packageName the name of the package from which to start scanning for
* classes, e.g. {@code net.sourceforge.stripes}
*/
public void findInPackage(Test test, String packageName) {
packageName = packageName.replace('.', '/');
ClassLoader loader = getClassLoader();
Enumeration urls;
try {
urls = loader.getResources(packageName);
}
catch (IOException ioe) {
log.warn("Could not read package: " + packageName, ioe);
return;
}
while (urls.hasMoreElements()) {
try {
String urlPath = urls.nextElement().getFile();
urlPath = URLDecoder.decode(urlPath, "UTF-8");
// If it's a file in a directory, trim the stupid file: spec
if ( urlPath.startsWith("file:") ) {
urlPath = urlPath.substring(5);
}
// Else it's in a JAR, grab the path to the jar
if (urlPath.indexOf('!') > 0) {
urlPath = urlPath.substring(0, urlPath.indexOf('!'));
}
log.info("Scanning for classes in [" + urlPath + "] matching criteria: " + test);
File file = new File(urlPath);
if ( file.isDirectory() ) {
loadImplementationsInDirectory(test, packageName, file);
}
else {
loadImplementationsInJar(test, packageName, file);
}
}
catch (IOException ioe) {
log.warn("could not read entries", ioe);
}
}
}
/**
* Finds matches in a physical directory on a filesystem. Examines all
* files within a directory - if the File object is not a directory, and ends with .class
* the file is loaded and tested to see if it is acceptable according to the Test. Operates
* recursively to find classes within a folder structure matching the package structure.
*
* @param test a Test used to filter the classes that are discovered
* @param parent the package name up to this directory in the package hierarchy. E.g. if
* /classes is in the classpath and we wish to examine files in /classes/org/apache then
* the values of parent would be org/apache
* @param location a File object representing a directory
*/
private void loadImplementationsInDirectory(Test test, String parent, File location) {
File[] files = location.listFiles();
StringBuilder builder = null;
for (File file : files) {
builder = new StringBuilder(100);
builder.append(parent).append("/").append(file.getName());
String packageOrClass = ( parent == null ? file.getName() : builder.toString() );
if (file.isDirectory()) {
loadImplementationsInDirectory(test, packageOrClass, file);
}
else if (file.getName().endsWith(".class")) {
addIfMatching(test, packageOrClass);
}
}
}
/**
* Finds matching classes within a jar files that contains a folder structure
* matching the package structure. If the File is not a JarFile or does not exist a warning
* will be logged, but no error will be raised.
*
* @param test a Test used to filter the classes that are discovered
* @param parent the parent package under which classes must be in order to be considered
* @param jarfile the jar file to be examined for classes
*/
private void loadImplementationsInJar(Test test, String parent, File jarfile) {
try {
JarEntry entry;
JarInputStream jarStream = new JarInputStream(new FileInputStream(jarfile));
while ( (entry = jarStream.getNextJarEntry() ) != null) {
String name = entry.getName();
if (!entry.isDirectory() && name.startsWith(parent) && name.endsWith(".class")) {
addIfMatching(test, name);
}
}
}
catch (IOException ioe) {
log.error("Could not search jar file '" + jarfile + "' for classes matching criteria: " +
test + " due to an IOException", ioe);
}
}
/**
* Add the class designated by the fully qualified class name provided to the set of
* resolved classes if and only if it is approved by the Test supplied.
*
* @param test the test used to determine if the class matches
* @param fqn the fully qualified name of a class
*/
protected void addIfMatching(Test test, String fqn) {
try {
String externalName = fqn.substring(0, fqn.indexOf('.')).replace('/', '.');
ClassLoader loader = getClassLoader();
if (log.isDebugEnabled()) {
log.debug("Checking to see if class " + externalName + " matches criteria [" + test + "]");
}
Class type = loader.loadClass(externalName);
if (test.matches(type) ) {
matches.add( (Class) type);
}
}
catch (Throwable t) {
log.warn("Could not examine class '" + fqn + "' due to a " +
t.getClass().getName() + " with message: " + t.getMessage());
}
}
}