/*
* Copyright 2009-2012 the original author or authors.
*
* 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 org.apache.ibatis.io;
import java.io.IOException;
import java.lang.annotation.Annotation;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import java.util.regex.Pattern;
import org.apache.commons.lang.StringUtils;
import org.apache.ibatis.logging.Log;
import org.apache.ibatis.logging.LogFactory;
/**
* <p>
* 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.
* </p>
* <p/>
* <p>
* 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.
* </p>
* <p/>
* <p>
* General searches are initiated by calling the
* {@link #find(org.apache.ibatis.io.ResolverUtil.Test, String)} ()} method and
* supplying a package name and a Test instance. This will cause the named
* package <b>and all sub-packages</b> 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.
* </p>
* <p/>
* <p>
* The standard usage pattern for the ResolverUtil class is as follows:
* </p>
* <p/>
*
* <pre>
* 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();
* </pre>
*
* @author Tim Fennell
*/
public class ResolverUtil<T> {
/*
* 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 is annotated with a specific
* annotation. If it is, then the test returns true, otherwise false.
*/
public static class AnnotatedWith implements Test {
private Class<? extends Annotation> annotation;
/** Constructs an AnnotatedWith test for the specified annotation type. */
public AnnotatedWith(Class<? extends Annotation> 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<Class<? extends T>> matches = new HashSet<Class<? extends T>>();
/**
* 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<Class<? extends T>> 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 ResolverUtil<T> findImplementations(Class<?> parent, String... packageNames) {
if (packageNames == null)
return this;
Test test = new IsA(parent);
for (String pkg : packageNames) {
find(test, pkg);
}
return this;
}
/**
* Attempts to discover classes that are annotated with 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 ResolverUtil<T> findAnnotated(Class<? extends Annotation> annotation, String... packageNames) {
if (packageNames == null)
return this;
Test test = new AnnotatedWith(annotation);
for (String pkg : packageNames) {
find(test, pkg);
}
return this;
}
/**
* 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 ResolverUtil<T> find(Test test, String packageName) {
String path = getPackagePath(packageName);
try {
List<String> children = VFS.getInstance().list(path);
for (String child : children) {
if (child.endsWith(".class"))
addIfMatching(test, child);
}
} catch (IOException ioe) {
log.error("Could not read package: " + packageName, ioe);
}
return this;
}
/**
* Converts a Java package name to a path that can be looked up with a call
* to {@link ClassLoader#getResources(String)}.
*
* @param packageName
* The Java package name to convert to a path
*/
protected String getPackagePath(String packageName) {
return packageName == null ? null : packageName.replace('.', '/');
}
/**
* 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
*/
@SuppressWarnings("unchecked")
protected void addIfMatching(Test test, String fqn) {
try {
String externalName = fqn.substring(0, fqn.indexOf('.')).replace('/', '.');
ClassLoader loader = getClassLoader();
log.debug("Checking to see if class " + externalName + " matches criteria [" + test + "]");
Class<?> type = loader.loadClass(externalName);
if (test.matches(type)) {
matches.add((Class<T>) type);
}
} catch (Throwable t) {
log.warn("Could not examine class '" + fqn + "'" + " due to a " + t.getClass().getName() + " with message: " + t.getMessage());
}
}
public static String trimComma(String para) {
if (StringUtils.isNotBlank(para)) {
if (para.endsWith(",")) {
return para.substring(0, para.length() - 1);
} else {
return para;
}
} else {
return "";
}
}
public static boolean isNumeric1(String str) {
Pattern pattern = Pattern.compile("[0-9]*");
return pattern.matcher(str).matches();
}
}