com.ovea.tajin.framework.jmx.ClassUtils Maven / Gradle / Ivy
/**
* Copyright (C) 2011 Ovea
*
* 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.ovea.tajin.framework.jmx;
import java.lang.reflect.Array;
import java.util.Arrays;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
/**
* @author Mathieu Carbou ([email protected])
*/
public final class ClassUtils {
private ClassUtils() {
}
/**
* Suffix for array class names: "[]"
*/
private 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";
/**
* The package separator character '.'
*/
private static final char PACKAGE_SEPARATOR = '.';
/**
* The inner class separator character '$'
*/
private static final char INNER_CLASS_SEPARATOR = '$';
/**
* The CGLIB class separator character "$$"
*/
private static final String CGLIB_CLASS_SEPARATOR = "$$";
/**
* 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>(16);
/**
* 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);
for (Map.Entry, Class> entry : primitiveWrapperTypeMap.entrySet()) {
registerCommonClasses(entry.getKey());
}
Set> primitiveTypes = new HashSet>(16);
primitiveTypes.addAll(primitiveWrapperTypeMap.values());
primitiveTypes.addAll(Arrays.asList(
boolean[].class, byte[].class, char[].class, double[].class,
float[].class, int[].class, long[].class, short[].class));
for (Class primitiveType : primitiveTypes) {
primitiveTypeNameMap.put(primitiveType.getName(), primitiveType);
}
registerCommonClasses(Boolean[].class, Byte[].class, Character[].class, Double[].class,
Float[].class, Integer[].class, Long[].class, Short[].class);
registerCommonClasses(Number.class, Number[].class, String.class, String[].class,
Object.class, Object[].class, Class.class, Class[].class);
registerCommonClasses(Throwable.class, Exception.class, RuntimeException.class,
Error.class, StackTraceElement.class, StackTraceElement[].class);
}
private static void registerCommonClasses(Class... commonClasses) {
for (Class clazz : commonClasses) {
commonClassCache.put(clazz.getName(), clazz);
}
}
/**
* 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 absolutely need a non-null ClassLoader reference:
* for example, for class path resource loading (but not necessarily for
* Class.forName, which accepts a null ClassLoader
* reference as well).
*
* @return the default ClassLoader (never null)
* @see Thread#getContextClassLoader()
*/
public static ClassLoader getDefaultClassLoader() {
ClassLoader cl = null;
try {
cl = Thread.currentThread().getContextClassLoader();
} catch (Throwable ex) {
// Cannot access thread context ClassLoader - falling back to system class loader...
}
if (cl == null) {
// No thread context class loader -> use class loader of this class.
cl = ClassUtils.class.getClassLoader();
}
return cl;
}
/**
* Replacement for 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$State").
*
* @param name the name of the Class
* @param classLoader the class loader to use
* (may be null, which indicates the default class loader)
* @return Class instance for the supplied name
* @throws ClassNotFoundException if the class was not found
* @throws LinkageError if the class file could not be loaded
* @see Class#forName(String, boolean, ClassLoader)
*/
public static Class forName(String name, ClassLoader classLoader) throws ClassNotFoundException, LinkageError {
Class clazz = resolvePrimitiveClassName(name);
if (clazz == null) {
clazz = commonClassCache.get(name);
}
if (clazz != null) {
return clazz;
}
// "java.lang.String[]" style arrays
if (name.endsWith(ARRAY_SUFFIX)) {
String elementClassName = name.substring(0, name.length() - ARRAY_SUFFIX.length());
Class elementClass = forName(elementClassName, classLoader);
return Array.newInstance(elementClass, 0).getClass();
}
// "[Ljava.lang.String;" style arrays
if (name.startsWith(NON_PRIMITIVE_ARRAY_PREFIX) && name.endsWith(";")) {
String elementName = name.substring(NON_PRIMITIVE_ARRAY_PREFIX.length(), name.length() - 1);
Class elementClass = forName(elementName, classLoader);
return Array.newInstance(elementClass, 0).getClass();
}
// "[[I" or "[[Ljava.lang.String;" style arrays
if (name.startsWith(INTERNAL_ARRAY_PREFIX)) {
String elementName = name.substring(INTERNAL_ARRAY_PREFIX.length());
Class elementClass = forName(elementName, classLoader);
return Array.newInstance(elementClass, 0).getClass();
}
ClassLoader classLoaderToUse = classLoader;
if (classLoaderToUse == null) {
classLoaderToUse = getDefaultClassLoader();
}
try {
return classLoaderToUse.loadClass(name);
} catch (ClassNotFoundException ex) {
int lastDotIndex = name.lastIndexOf('.');
if (lastDotIndex != -1) {
String innerClassName = name.substring(0, lastDotIndex) + '$' + name.substring(lastDotIndex + 1);
try {
return classLoaderToUse.loadClass(innerClassName);
} catch (ClassNotFoundException ex2) {
// swallow - let original exception get through
}
}
throw 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 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;
}
/**
* Determine whether the {@link Class} identified by the supplied name is present
* and can be loaded. Will return 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 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;
}
}
/**
* 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) {
int lastDotIndex = className.lastIndexOf(PACKAGE_SEPARATOR);
int nameEndIndex = className.indexOf(CGLIB_CLASS_SEPARATOR);
if (nameEndIndex == -1) {
nameEndIndex = className.length();
}
String shortName = className.substring(lastDotIndex + 1, nameEndIndex);
shortName = shortName.replace(INNER_CLASS_SEPARATOR, PACKAGE_SEPARATOR);
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));
}
/**
* Determine the name of the package of the given class:
* e.g. "java.lang" for the java.lang.String class.
*
* @param clazz the class
* @return the package name, or the empty String if the class
* is defined in the default package
*/
public static String getPackageName(Class clazz) {
String className = clazz.getName();
int lastDotIndex = className.lastIndexOf(PACKAGE_SEPARATOR);
return (lastDotIndex != -1 ? className.substring(0, lastDotIndex) : "");
}
/**
* 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) {
if (clazz.isArray()) {
return getQualifiedNameForArray(clazz);
} else {
return clazz.getName();
}
}
/**
* Build a nice qualified name for an array:
* component type class name + "[]".
*
* @param clazz the array class
* @return a qualified name for the array class
*/
private static String getQualifiedNameForArray(Class clazz) {
StringBuilder result = new StringBuilder();
while (clazz.isArray()) {
clazz = clazz.getComponentType();
result.append(ClassUtils.ARRAY_SUFFIX);
}
result.insert(0, clazz.getName());
return result.toString();
}
/**
* Check if the right-hand side type may be assigned to the left-hand side
* type, assuming setting by reflection. Considers primitive wrapper
* classes as assignable to the corresponding primitive types.
*
* @param lhsType the target type
* @param rhsType the value type that should be assigned to the target type
* @return if the target type is assignable from the value type
*/
public static boolean isAssignable(Class lhsType, Class rhsType) {
return (lhsType.isAssignableFrom(rhsType) ||
lhsType.equals(primitiveWrapperTypeMap.get(rhsType)));
}
/**
* Determine if the given type is assignable from the given value,
* assuming setting by reflection. Considers primitive wrapper classes
* as assignable to the corresponding primitive types.
*
* @param type the target type
* @param value the value that should be assigned to the type
* @return if the type is assignable from the value
*/
public static boolean isAssignableValue(Class type, Object value) {
return (value != null ? isAssignable(type, value.getClass()) : !type.isPrimitive());
}
}