获取指定package下指定类的子类:
/**
* 获取指定package下 superType 的子类
* @param packageName 包名
* @param superType 指定类
* @return 指定package下 superType 的所有子类
*/
public static Set<Class<? extends Class<?>>> getChildrenClasses(String packageName, Class<?> superType) {
ResolverUtil<Class<?>> resolverUtil = new ResolverUtil<Class<?>>();
resolverUtil.find(new ResolverUtil.IsA(superType), packageName);
Set<Class<? extends Class<?>>> classes = resolverUtil.getClasses();
// Set<Class<? extends Class<?>>> results = new HashSet<Class<? extends Class<?>>>();
// for (Class<? extends Class<?>> clazz : classes) {
// //过滤掉 匿名内部类、接口 以及 抽象类
// if (!clazz.isAnonymousClass() && !clazz.isInterface() && !Modifier.isAbstract(clazz.getModifiers())) {
// results.add(clazz);
// }
// }
return classes;
}
}
ResolverUtil 类:
import java.io.IOException;
import java.lang.annotation.Annotation;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import org.apache.ibatis.logging.Log;
import org.apache.ibatis.logging.LogFactory;
/**
* 根据指定的条件查找指定包下的类,其中使用的条件由 Test 接口表示
*/
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. */
@Override
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. */
@Override
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();
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<T>) type);
}
} catch (Throwable t) {
log.warn("Could not examine class '" + fqn + "'" + " due to a " +
t.getClass().getName() + " with message: " + t.getMessage());
}
}
}
VFS 类:在调用 ResolverUtil#find(Test test, String packageName)
方法时,需要查找 packageName 包下的所有资源,就是通过调用 VFS 来实现的,具体实现如下:
package org.apache.ibatis.io;
import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.net.URL;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import org.apache.ibatis.logging.Log;
import org.apache.ibatis.logging.LogFactory;
/**
* 1.VFS 是虚拟文件系统通用API,不需关心什么存储媒介
* 2.优先使用自定义实现VFS,最后使用mybatis内置的 JBoss6VFS, DefaultVFS
* 3.VFS 是单例模式,根据顺序:自定义实现VFS > 内置原则:实例VFS
*/
public abstract class VFS {
/**
* 日志
*/
private static final Log log = LogFactory.getLog(VFS.class);
/**
* Mybatis 内置实现:JBoss6VFS, DefaultVFS
*/
public static final Class<?>[] IMPLEMENTATIONS = { JBoss6VFS.class, DefaultVFS.class };
/**
* 用户自定义实现的 VFS 的类
*/
public static final List<Class<? extends VFS>> USER_IMPLEMENTATIONS = new ArrayList<Class<? extends VFS>>();
/** Singleton instance. */
private static VFS instance;
/**
* Get the singleton {@link VFS} instance. If no {@link VFS} implementation can be found for the
* current environment, then this method returns null.
*/
@SuppressWarnings("unchecked")
public static VFS getInstance() {
if (instance != null) {
return instance;
}
// Try the user implementations first, then the built-ins
List<Class<? extends VFS>> impls = new ArrayList<Class<? extends VFS>>();
//先加入用户自定义实现的 VFS
impls.addAll(USER_IMPLEMENTATIONS);
//加载 mybatis 内置实现的 VFS
impls.addAll(Arrays.asList((Class<? extends VFS>[]) IMPLEMENTATIONS));
// Try each implementation class until a valid one is found
VFS vfs = null;
for (int i = 0; vfs == null || !vfs.isValid(); i++) {
//循环遍历,直到找到有效 VFS 实现类
Class<? extends VFS> impl = impls.get(i);
try {
//实例化
vfs = impl.newInstance();
if (vfs == null || !vfs.isValid()) {
if (log.isDebugEnabled()) {
log.debug("VFS implementation " + impl.getName() +
" is not valid in this environment.");
}
}
} catch (InstantiationException e) {
log.error("Failed to instantiate " + impl, e);
return null;
} catch (IllegalAccessException e) {
log.error("Failed to instantiate " + impl, e);
return null;
}
}
if (log.isDebugEnabled()) {
log.debug("Using VFS adapter " + vfs.getClass().getName());
}
VFS.instance = vfs;
return VFS.instance;
}
/**
* Adds the specified class to the list of {@link VFS} implementations. Classes added in this
* manner are tried in the order they are added and before any of the built-in implementations.
*
* @param clazz The {@link VFS} implementation class to add.
*/
public static void addImplClass(Class<? extends VFS> clazz) {
if (clazz != null) {
USER_IMPLEMENTATIONS.add(clazz);
}
}
/**
* 用当前线程绑定的类加载器加载目标类
*/
protected static Class<?> getClass(String className) {
try {
return Thread.currentThread().getContextClassLoader().loadClass(className);
// return ReflectUtil.findClass(className);
} catch (ClassNotFoundException e) {
if (log.isDebugEnabled()) {
log.debug("Class not found: " + className);
}
return null;
}
}
/**
* 通过类、方法名、方法参数类型获取对应参数
*/
protected static Method getMethod(Class<?> clazz, String methodName, Class<?>... parameterTypes) {
if (clazz == null) {
return null;
}
try {
return clazz.getMethod(methodName, parameterTypes);
} catch (SecurityException e) {
log.error("Security exception looking for method " + clazz.getName() + "." + methodName + ". Cause: " + e);
return null;
} catch (NoSuchMethodException e) {
log.error("Method not found " + clazz.getName() + "." + methodName + "." + methodName + ". Cause: " + e);
return null;
}
}
/**
* 调用方法
*/
@SuppressWarnings("unchecked")
protected static <T> T invoke(Method method, Object object, Object... parameters)
throws IOException, RuntimeException {
try {
return (T) method.invoke(object, parameters);
} catch (IllegalArgumentException e) {
throw new RuntimeException(e);
} catch (IllegalAccessException e) {
throw new RuntimeException(e);
} catch (InvocationTargetException e) {
if (e.getTargetException() instanceof IOException) {
throw (IOException) e.getTargetException();
} else {
throw new RuntimeException(e);
}
}
}
/**
* 在特定路径下加载所有资源 URL 返回
*/
protected static List<URL> getResources(String path) throws IOException {
return Collections.list(Thread.currentThread().getContextClassLoader().getResources(path));
}
/**
* 判断 是否有效
*/
public abstract boolean isValid();
/**
* 递归列出URL的下所有子的资源列表
*/
protected abstract List<String> list(URL url, String forPath) throws IOException;
/**
* 列出某个路径所有 URL 对应 子资源
*/
public List<String> list(String path) throws IOException {
List<String> names = new ArrayList<String>();
for (URL url : getResources(path)) {
names.addAll(list(url, path));
}
return names;
}
}