org.devefx.validator.util.ClassUtils Maven / Gradle / Ivy
Show all versions of validator-web Show documentation
/*
* Copyright 2016-2017, Youqian Yue ([email protected]).
*
* 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.devefx.validator.util;
import java.lang.reflect.Array;
import java.util.HashMap;
import java.util.Map;
/**
* Miscellaneous class utility methods.
* Mainly for internal use within the framework.
*/
public class ClassUtils {
/** Suffix for array class names: "[]" */
public static final String ARRAY_SUFFIX = "[]";
/** Prefix for internal array class names: "[" */
private static final String INTERNAL_ARRAY_PREFIX = "[";
/** Prefix for internal non-primitive array class names: "[L" */
private static final String NON_PRIMITIVE_ARRAY_PREFIX = "[L";
/**
* Map with primitive wrapper type as key and corresponding primitive
* type as value, for example: Integer.class -> int.class.
*/
private static final Map, Class> primitiveWrapperTypeMap = new HashMap, Class>(8);
/**
* Map with primitive type name as key and corresponding primitive
* type as value, for example: "int" -> "int.class".
*/
private static final Map> primitiveTypeNameMap = new HashMap>(32);
/**
* Map with common "java.lang" class name as key and corresponding Class as value.
* Primarily for efficient deserialization of remote invocations.
*/
private static final Map> commonClassCache = new HashMap>(32);
static {
primitiveWrapperTypeMap.put(Boolean.class, boolean.class);
primitiveWrapperTypeMap.put(Byte.class, byte.class);
primitiveWrapperTypeMap.put(Character.class, char.class);
primitiveWrapperTypeMap.put(Double.class, double.class);
primitiveWrapperTypeMap.put(Float.class, float.class);
primitiveWrapperTypeMap.put(Integer.class, int.class);
primitiveWrapperTypeMap.put(Long.class, long.class);
primitiveWrapperTypeMap.put(Short.class, short.class);
}
/**
* Return the default ClassLoader to use: typically the thread context
* ClassLoader, if available; the ClassLoader that loaded the ClassUtils
* class will be used as fallback.
* Call this method if you intend to use the thread context ClassLoader
* in a scenario where you clearly prefer a non-null ClassLoader reference:
* for example, for class path resource loading (but not necessarily for
* {@code Class.forName}, which accepts a {@code null} ClassLoader
* reference as well).
* @return the default ClassLoader (only {@code null} if even the system
* ClassLoader isn't accessible)
* @see Thread#getContextClassLoader()
* @see ClassLoader#getSystemClassLoader()
*/
public static ClassLoader getDefaultClassLoader() {
ClassLoader cl = null;
try {
cl = Thread.currentThread().getContextClassLoader();
} catch (Throwable ex) {
// Cannot access thread context ClassLoader - falling back...
}
if (cl == null) {
// No thread context class loader -> use class loader of this class.
cl = ClassUtils.class.getClassLoader();
if (cl == null) {
// getClassLoader() returning null indicates the bootstrap ClassLoader
try {
cl = ClassLoader.getSystemClassLoader();
}
catch (Throwable ex) {
// Cannot access system ClassLoader - oh well, maybe the caller can live with null...
}
}
}
return cl;
}
/**
* Determine whether the {@link Class} identified by the supplied name is present
* and can be loaded. Will return {@code false} if either the class or
* one of its dependencies is not present or cannot be loaded.
* @param className the name of the class to check
* @param classLoader the class loader to use
* (may be {@code null}, which indicates the default class loader)
* @return whether the specified class is present
*/
public static boolean isPresent(String className, ClassLoader classLoader) {
try {
forName(className, classLoader);
return true;
}
catch (Throwable ex) {
// Class or one of its dependencies is not present...
return false;
}
}
/**
* Replacement for {@code Class.forName()} that also returns Class instances
* for primitives (e.g. "int") and array class names (e.g. "String[]").
* Furthermore, it is also capable of resolving inner class names in Java source
* style (e.g. "java.lang.Thread.State" instead of "java.lang.Thread$State").
* @param name the name of the Class
* @return Class instance for the supplied name
* @throws ClassNotFoundException if the class was not found
* @throws LinkageError if the class file could not be loaded
* @see Class#forName(String, boolean, ClassLoader)
*/
public static Class forName(String name) throws ClassNotFoundException, LinkageError {
return forName(name, getDefaultClassLoader());
}
/**
* Replacement for {@code Class.forName()} that also returns Class instances
* for primitives (e.g. "int") and array class names (e.g. "String[]").
* Furthermore, it is also capable of resolving inner class names in Java source
* style (e.g. "java.lang.Thread.State" instead of "java.lang.Thread$State").
* @param name the name of the Class
* @param classLoader the class loader to use
* (may be {@code null}, which indicates the default class loader)
* @return Class instance for the supplied name
* @throws ClassNotFoundException if the class was not found
* @throws LinkageError if the class file could not be loaded
* @see Class#forName(String, boolean, ClassLoader)
*/
public static Class forName(String name, ClassLoader classLoader) throws ClassNotFoundException, LinkageError {
Assert.notNull(name, "Name must not be null");
Class clazz = resolvePrimitiveClassName(name);
if (clazz == null) {
clazz = commonClassCache.get(name);
}
if (clazz != null) {
return clazz;
}
// "java.lang.String[]" style arrays
if (name.endsWith(ARRAY_SUFFIX)) {
String elementClassName = name.substring(0, name.length() - ARRAY_SUFFIX.length());
Class elementClass = forName(elementClassName, classLoader);
return Array.newInstance(elementClass, 0).getClass();
}
// "[Ljava.lang.String;" style arrays
if (name.startsWith(NON_PRIMITIVE_ARRAY_PREFIX) && name.endsWith(";")) {
String elementName = name.substring(NON_PRIMITIVE_ARRAY_PREFIX.length(), name.length() - 1);
Class elementClass = forName(elementName, classLoader);
return Array.newInstance(elementClass, 0).getClass();
}
// "[[I" or "[[Ljava.lang.String;" style arrays
if (name.startsWith(INTERNAL_ARRAY_PREFIX)) {
String elementName = name.substring(INTERNAL_ARRAY_PREFIX.length());
Class elementClass = forName(elementName, classLoader);
return Array.newInstance(elementClass, 0).getClass();
}
ClassLoader clToUse = classLoader;
if (clToUse == null) {
clToUse = getDefaultClassLoader();
}
try {
return (clToUse != null ? clToUse.loadClass(name) : Class.forName(name));
} catch (ClassNotFoundException ex) {
int lastDotIndex = name.lastIndexOf('.');
if (lastDotIndex != -1) {
String innerClassName = name.substring(0, lastDotIndex) + '$' + name.substring(lastDotIndex + 1);
try {
return (clToUse != null ? clToUse.loadClass(innerClassName) : Class.forName(innerClassName));
}
catch (ClassNotFoundException ex2) {
// swallow - let original exception get through
}
}
throw ex;
}
}
/**
* Resolve the given class name into a Class instance. Supports
* primitives (like "int") and array class names (like "String[]").
*
This is effectively equivalent to the {@code forName}
* method with the same arguments, with the only difference being
* the exceptions thrown in case of class loading failure.
* @param className the name of the Class
* @param classLoader the class loader to use
* (may be {@code null}, which indicates the default class loader)
* @return Class instance for the supplied name
* @throws IllegalArgumentException if the class name was not resolvable
* (that is, the class could not be found or the class file could not be loaded)
* @see #forName(String, ClassLoader)
*/
public static Class resolveClassName(String className, ClassLoader classLoader) throws IllegalArgumentException {
try {
return forName(className, classLoader);
} catch (ClassNotFoundException ex) {
throw new IllegalArgumentException("Cannot find class [" + className + "]", ex);
} catch (LinkageError ex) {
throw new IllegalArgumentException(
"Error loading class [" + className + "]: problem with class file or dependent class.", ex);
}
}
/**
* Resolve the given class name as primitive class, if appropriate,
* according to the JVM's naming rules for primitive classes.
*
Also supports the JVM's internal class names for primitive arrays.
* Does not support the "[]" suffix notation for primitive arrays;
* this is only supported by {@link #forName(String, ClassLoader)}.
* @param name the name of the potentially primitive class
* @return the primitive class, or {@code null} if the name does not denote
* a primitive class or primitive array class
*/
public static Class resolvePrimitiveClassName(String name) {
Class result = null;
// Most class names will be quite long, considering that they
// SHOULD sit in a package, so a length check is worthwhile.
if (name != null && name.length() <= 8) {
// Could be a primitive - likely.
result = primitiveTypeNameMap.get(name);
}
return result;
}
/**
* Check if the given class represents a primitive (i.e. boolean, byte,
* char, short, int, long, float, or double) or a primitive wrapper
* (i.e. Boolean, Byte, Character, Short, Integer, Long, Float, or Double).
* @param clazz the class to check
* @return whether the given class is a primitive or primitive wrapper class
*/
public static boolean isPrimitiveOrWrapper(Class clazz) {
Assert.notNull(clazz, "Class must not be null");
return (clazz.isPrimitive() || isPrimitiveWrapper(clazz));
}
/**
* Check if the given class represents a primitive wrapper,
* i.e. Boolean, Byte, Character, Short, Integer, Long, Float, or Double.
* @param clazz the class to check
* @return whether the given class is a primitive wrapper class
*/
public static boolean isPrimitiveWrapper(Class clazz) {
Assert.notNull(clazz, "Class must not be null");
return primitiveWrapperTypeMap.containsKey(clazz);
}
public static Object newInstance(String className) throws InstantiationException, IllegalAccessException,
ClassNotFoundException, LinkageError {
return newInstance(forName(className));
}
public static Object newInstance(Class clazz) throws InstantiationException, IllegalAccessException {
if (clazz == null) {
String msg = "Class method parameter cannot be null.";
throw new IllegalArgumentException(msg);
}
return clazz.newInstance();
}
}