classutils.java

spring的源代码

/*
 * Copyright 2002-2006 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.springframework.util;

import java.beans.Introspector;
import java.lang.reflect.Array;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.Collections;
import java.util.HashSet;
import java.util.Set;

/**
 * Miscellaneous class utility methods. Mainly for internal use within the
 * framework; consider Jakarta's Commons Lang for a more comprehensive suite
 * of utilities.
 *
 * @author Keith Donald
 * @author Rob Harrop
 * @author Juergen Hoeller
 * @since 1.1
 */
public abstract class ClassUtils {

	/** Suffix for array class names */
	public static final String ARRAY_SUFFIX = "[]";

	/** All primitive classes */
	private static Class[] PRIMITIVE_CLASSES = {
		boolean.class, byte.class, char.class, short.class, int.class, long.class, float.class, double.class};

	/** The package separator character '.' */
	private static final char PACKAGE_SEPARATOR_CHAR = '.';

	/** The inner class separator character '$' */
	private static final char INNER_CLASS_SEPARATOR_CHAR = '$';

	/** The CGLIB class separator character "$$" */
	private static final String CGLIB_CLASS_SEPARATOR_CHAR = "$$";


	/**
	 * Return a default ClassLoader to use (never <code>null</code>).
	 * Returns the thread context ClassLoader, if available.
	 * The ClassLoader that loaded the ClassUtils class will be used as fallback.
	 * <p>Call this method if you intend to use the thread context ClassLoader
	 * in a scenario where you absolutely need a non-null ClassLoader reference:
	 * for example, for class path resource loading (but not necessarily for
	 * <code>Class.forName</code>, which accepts a <code>null</code> ClassLoader
	 * reference as well).
	 * @see java.lang.Thread#getContextClassLoader()
	 */
	public static ClassLoader getDefaultClassLoader() {
		ClassLoader cl = Thread.currentThread().getContextClassLoader();
		if (cl == null) {
			// No thread context class loader -> use class loader of this class.
			cl = ClassUtils.class.getClassLoader();
		}
		return cl;
	}

	/**
	 * Replacement for <code>Class.forName()</code> that also returns Class instances
	 * for primitives (like "int") and array class names (like "String[]").
	 * <p>Always uses the default class loader: that is, preferably the thread context
	 * class loader, or the ClassLoader that loaded the ClassUtils class as fallback.
	 * @param name the name of the Class
	 * @return Class instance for the supplied name
	 * @see java.lang.Class#forName(String, boolean, ClassLoader)
	 * @see #getDefaultClassLoader()
	 */
	public static Class forName(String name) throws ClassNotFoundException {
		return forName(name, getDefaultClassLoader());
	}

	/**
	 * Replacement for <code>Class.forName()</code> that also returns Class instances
	 * for primitives (like "int") and array class names (like "String[]").
	 * @param name the name of the Class
	 * @param classLoader the class loader to use
	 * @return Class instance for the supplied name
	 * @see java.lang.Class#forName(String, boolean, ClassLoader)
	 */
	public static Class forName(String name, ClassLoader classLoader) throws ClassNotFoundException {
		Class clazz = resolvePrimitiveClassName(name);
		if (clazz != null) {
			return clazz;
		}
		if (name.endsWith(ARRAY_SUFFIX)) {
			// special handling for array class names
			String elementClassName = name.substring(0, name.length() - ARRAY_SUFFIX.length());
			Class elementClass = ClassUtils.forName(elementClassName, classLoader);
			return Array.newInstance(elementClass, 0).getClass();
		}
		return Class.forName(name, true, classLoader);
	}

	/**
	 * Resolve the given class name as primitive class, if appropriate.
	 * @param name the name of the potentially primitive class
	 * @return the primitive class, or <code>null</code> if the name does not denote
	 * a primitive class
	 */
	public static Class resolvePrimitiveClassName(String name) {
		// Most class names will be quite long, considering that they
		// SHOULD sit in a package, so a length check is worthwhile.
		if (name.length() <= 8) {
			// could be a primitive - likely
			for (int i = 0; i < PRIMITIVE_CLASSES.length; i++) {
				Class clazz = PRIMITIVE_CLASSES[i];
				if (clazz.getName().equals(name)) {
					return clazz;
				}
			}
		}
		return null;
	}

	/**
	 * Get the class name without the qualified package name.
	 * @param className the className to get the short name for
	 * @return the class name of the class without the package name
	 * @throws IllegalArgumentException if the className is empty
	 */
	public static String getShortName(String className) {
		Assert.hasLength(className, "Class name must not be empty");
		int lastDotIndex = className.lastIndexOf(PACKAGE_SEPARATOR_CHAR);
		int nameEndIndex = className.indexOf(CGLIB_CLASS_SEPARATOR_CHAR);
		if (nameEndIndex == -1) {
			nameEndIndex = className.length();
		}
		String shortName = className.substring(lastDotIndex + 1, nameEndIndex);
		shortName = shortName.replace(INNER_CLASS_SEPARATOR_CHAR, PACKAGE_SEPARATOR_CHAR);
		return shortName;
	}

	/**
	 * Get the class name without the qualified package name.
	 * @param clazz the class to get the short name for
	 * @return the class name of the class without the package name
	 */
	public static String getShortName(Class clazz) {
		return getShortName(getQualifiedName(clazz));
	}

	/**
	 * Return the short string name of a Java class in decapitalized
	 * JavaBeans property format.
	 * @param clazz the class
	 * @return the short name rendered in a standard JavaBeans property format
	 * @see java.beans.Introspector#decapitalize(String)
	 */
	public static String getShortNameAsProperty(Class clazz) {
		return Introspector.decapitalize(getShortName(clazz));
	}

	/**
	 * Return the qualified name of the given class: usually simply
	 * the class name, but component type class name + "[]" for arrays.
	 * @param clazz the class
	 * @return the qualified name of the class
	 */
	public static String getQualifiedName(Class clazz) {
		Assert.notNull(clazz, "Class must not be null");
		if (clazz.isArray()) {
			return clazz.getComponentType().getName() + ARRAY_SUFFIX;
		}
		else {
			return clazz.getName();
		}
	}


	/**
	 * Return the qualified name of the given method, consisting of
	 * fully qualified interface/class name + "." + method name.
	 * @param method the method
	 * @return the qualified name of the method
	 */
	public static String getQualifiedMethodName(Method method) {
		Assert.notNull(method, "Method must not be empty");
		return method.getDeclaringClass().getName() + "." + method.getName();
	}

	/**
	 * Determine whether the given class has a method with the given signature.
	 * Essentially translates <code>NoSuchMethodException</code> to "false".
	 * @param clazz the clazz to analyze
	 * @param methodName the name of the method
	 * @param paramTypes the parameter types of the method
	 */
	public static boolean hasMethod(Class clazz, String methodName, Class[] paramTypes) {
		Assert.notNull(clazz, "Class must not be null");
		Assert.notNull(methodName, "Method name must not be null");
		try {
			clazz.getMethod(methodName, paramTypes);
			return true;
		}
		catch (NoSuchMethodException ex) {
			return false;
		}
	}

	/**
	 * Return the number of methods with a given name (with any argument types),
	 * for the given class and/or its superclasses. Includes non-public methods.
	 * @param clazz the clazz to check
	 * @param methodName the name of the method
	 * @return the number of methods with the given name
	 */
	public static int getMethodCountForName(Class clazz, String methodName) {
		Assert.notNull(clazz, "Class must not be null");
		Assert.notNull(methodName, "Method name must not be null");
		int count = 0;
		do {
			for (int i = 0; i < clazz.getDeclaredMethods().length; i++) {
				Method method = clazz.getDeclaredMethods()[i];
				if (methodName.equals(method.getName())) {
					count++;
				}
			}
			clazz = clazz.getSuperclass();
		}
		while (clazz != null);
		return count;
	}

	/**
	 * Does the given class and/or its superclasses at least have one or more
	 * methods (with any argument types)? Includes non-public methods.
	 * @param clazz the clazz to check
	 * @param methodName the name of the method
	 * @return whether there is at least one method with the given name
	 */
	public static boolean hasAtLeastOneMethodWithName(Class clazz, String methodName) {
		Assert.notNull(clazz, "Class must not be null");
		Assert.notNull(methodName, "Method name must not be null");
		do {
			for (int i = 0; i < clazz.getDeclaredMethods().length; i++) {
				Method method = clazz.getDeclaredMethods()[i];
				if (method.getName().equals(methodName)) {
					return true;
				}
			}
			clazz = clazz.getSuperclass();
		}
		while (clazz != null);
		return false;
	}

	/**
	 * Return a static method of a class.
	 * @param methodName the static method name
	 * @param clazz the class which defines the method
	 * @param args the parameter types to the method
	 * @return the static method, or <code>null</code> if no static method was found
	 * @throws IllegalArgumentException if the method name is blank or the clazz is null
	 */
	public static Method getStaticMethod(Class clazz, String methodName, Class[] args) {
		Assert.notNull(clazz, "Class must not be null");
		Assert.notNull(methodName, "Method name must not be null");
		try {
			Method method = clazz.getDeclaredMethod(methodName, args);
			if ((method.getModifiers() & Modifier.STATIC) != 0) {
				return method;
			}
		} catch (NoSuchMethodException ex) {
		}
		return null;
	}


	/**
	 * Return a path suitable for use with <code>ClassLoader.getResource</code>
	 * (also suitable for use with <code>Class.getResource</code> by prepending a
	 * slash ('/') to the return value. Built by taking the package of the specified
	 * class file, converting all dots ('.') to slashes ('/'), adding a trailing slash
	 * if necesssary, and concatenating the specified resource name to this.
	 * <br/>As such, this function may be used to build a path suitable for
	 * loading a resource file that is in the same package as a class file,
	 * although {@link org.springframework.core.io.ClassPathResource} is usually
	 * even more convenient.
	 * @param clazz the Class whose package will be used as the base
	 * @param resourceName the resource name to append. A leading slash is optional.
	 * @return the built-up resource path
	 * @see java.lang.ClassLoader#getResource
	 * @see java.lang.Class#getResource
	 */
	public static String addResourcePathToPackagePath(Class clazz, String resourceName) {
		Assert.notNull(resourceName, "Resource name must not be null");
		if (!resourceName.startsWith("/")) {
			return classPackageAsResourcePath(clazz) + "/" + resourceName;
		}
		return classPackageAsResourcePath(clazz) + resourceName;
	}

	/**
	 * Given an input class object, return a string which consists of the
	 * class's package name as a pathname, i.e., all dots ('.') are replaced by
	 * slashes ('/'). Neither a leading nor trailing slash is added. The result
	 * could be concatenated with a slash and the name of a resource, and fed
	 * directly to ClassLoader.getResource(). For it to be fed to Class.getResource,
	 * a leading slash would also have to be prepended to the return value.
	 * @param clazz the input class. A null value or the default (empty) package
	 * will result in an empty string ("") being returned.
	 * @return a path which represents the package name
	 * @see java.lang.ClassLoader#getResource
	 * @see java.lang.Class#getResource
	 */
	public static String classPackageAsResourcePath(Class clazz) {
		if (clazz == null || clazz.getPackage() == null) {
			return "";
		}
		return clazz.getPackage().getName().replace('.', '/');
	}

	/**
	 * Return all interfaces that the given object implements as array,
	 * including ones implemented by superclasses.
	 * @param object the object to analyse for interfaces
	 * @return all interfaces that the given object implements as array
	 */
	public static Class[] getAllInterfaces(Object object) {
		Set interfaces = getAllInterfacesAsSet(object);
		return (Class[]) interfaces.toArray(new Class[interfaces.size()]);
	}

	/**
	 * Return all interfaces that the given class implements as array,
	 * including ones implemented by superclasses.
	 * <p>If the class itself is an interface, it gets returned as sole interface.
	 * @param clazz the class to analyse for interfaces
	 * @return all interfaces that the given object implements as array
	 */
	public static Class[] getAllInterfacesForClass(Class clazz) {
		Set interfaces = getAllInterfacesForClassAsSet(clazz);
		return (Class[]) interfaces.toArray(new Class[interfaces.size()]);
	}

	/**
	 * Return all interfaces that the given object implements as List,
	 * including ones implemented by superclasses.
	 * @param object the object to analyse for interfaces
	 * @return all interfaces that the given object implements as List
	 */
	public static Set getAllInterfacesAsSet(Object object) {
		return getAllInterfacesForClassAsSet(object.getClass());
	}

	/**
	 * Return all interfaces that the given class implements as Set,
	 * including ones implemented by superclasses.
	 * <p>If the class itself is an interface, it gets returned as sole interface.
	 * @param clazz the class to analyse for interfaces
	 * @return all interfaces that the given object implements as Set
	 */
	public static Set getAllInterfacesForClassAsSet(Class clazz) {
		if (clazz.isInterface()) {
			return Collections.singleton(clazz);
		}
		Set interfaces = new HashSet();
		while (clazz != null) {
			for (int i = 0; i < clazz.getInterfaces().length; i++) {
				Class ifc = clazz.getInterfaces()[i];
				interfaces.add(ifc);
			}
			clazz = clazz.getSuperclass();
		}
		return interfaces;
	}

}