com.github.fartherp.framework.common.util.ClassHelper Maven / Gradle / Ivy
/*
* Copyright (c) 2017. CK. All rights reserved.
*/
package com.github.fartherp.framework.common.util;
import java.lang.reflect.Array;
import java.util.Arrays;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
public class ClassHelper {
/**
* Suffix for array class names: "[]"
*/
public static final String ARRAY_SUFFIX = "[]";
/**
* Prefix for internal array class names: "[L"
*/
private static final String INTERNAL_ARRAY_PREFIX = "[L";
/**
* 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 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);
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);
Set> primitiveTypeNames = new HashSet>(16);
primitiveTypeNames.addAll(primitiveWrapperTypeMap.values());
primitiveTypeNames.addAll(Arrays
.asList(new Class[]{boolean[].class, byte[].class, char[].class, double[].class,
float[].class, int[].class, long[].class, short[].class}));
for (Iterator> it = primitiveTypeNames.iterator(); it.hasNext(); ) {
Class primitiveClass = (Class) it.next();
primitiveTypeNameMap.put(primitiveClass.getName(), primitiveClass);
}
}
public static Class forNameWithThreadContextClassLoader(String name)
throws ClassNotFoundException {
return forName(name, Thread.currentThread().getContextClassLoader());
}
public static Class forNameWithCallerClassLoader(String name, Class caller)
throws ClassNotFoundException {
return forName(name, caller.getClassLoader());
}
public static ClassLoader getCallerClassLoader(Class caller) {
return caller.getClassLoader();
}
/**
* get class loader
*
* @param cls
* @return class loader
*/
public static ClassLoader getClassLoader(Class cls) {
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 = cls.getClassLoader();
}
return cl;
}
/**
* 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 getClassLoader() {
return getClassLoader(ClassHelper.class);
}
/**
* Same as Class.forName(), except that it works for primitive
* types.
*/
public static Class forName(String name) throws ClassNotFoundException {
return forName(name, getClassLoader());
}
/**
* Replacement for Class.forName() 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 (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) {
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
int internalArrayMarker = name.indexOf(INTERNAL_ARRAY_PREFIX);
if (internalArrayMarker != -1 && name.endsWith(";")) {
String elementClassName = null;
if (internalArrayMarker == 0) {
elementClassName = name
.substring(INTERNAL_ARRAY_PREFIX.length(), name.length() - 1);
} else if (name.startsWith("[")) {
elementClassName = name.substring(1);
}
Class elementClass = forName(elementClassName, classLoader);
return Array.newInstance(elementClass, 0).getClass();
}
ClassLoader classLoaderToUse = classLoader;
if (classLoaderToUse == null) {
classLoaderToUse = getClassLoader();
}
return classLoaderToUse.loadClass(name);
}
/**
* 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}.
*
* @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 = (Class) primitiveTypeNameMap.get(name);
}
return result;
}
public static String toShortString(Object obj) {
if (obj == null) {
return "null";
}
return obj.getClass().getSimpleName() + "@" + System.identityHashCode(obj);
}
}