net.minidev.asm.DynamicClassLoader Maven / Gradle / Ivy

package net.minidev.asm;

/*
 *    Copyright 2011 JSON-SMART 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.
 */
import java.lang.reflect.Method;

/**
 * Simple extension from ClassLoader overiding the loadClass(String name,
 * boolean resolve) method and allowing to register new classes
 * 
 * @author uriel
 * 
 */
class DynamicClassLoader extends ClassLoader {
	DynamicClassLoader(ClassLoader parent) {
		super(parent);
	}

	private final static String BEAN_AC = BeansAccess.class.getName();
	/**
	 * Predefined define defineClass method signature (name, bytes, offset,
	 * length)
	 */
	private final static Class[] DEF_CLASS_SIG = new Class[] { String.class, byte[].class, int.class, int.class };

	/**
	 * 
	 * @param parent used to choose the ClassLoader
	 * @param clsName C
	 * @param clsData
	 * @return
	 */
	public static  Class directLoad(Class parent, String clsName, byte[] clsData) {
		DynamicClassLoader loader = new DynamicClassLoader(parent.getClassLoader());
		@SuppressWarnings("unchecked")
		Class clzz = (Class) loader.defineClass(clsName, clsData);
		return clzz;
	}

	public static  T directInstance(Class parent, String clsName, byte[] clsData) throws InstantiationException, IllegalAccessException {
		Class clzz = directLoad(parent, clsName, clsData);
		return clzz.newInstance();
	}

	@Override
	protected synchronized java.lang.Class loadClass(String name, boolean resolve) throws ClassNotFoundException {
		/*
		 * check class by fullname as String.
		 */
		if (name.equals(BEAN_AC))
			return BeansAccess.class;
		/*
		 * Use default class loader
		 */
		return super.loadClass(name, resolve);
	}

	/**
	 * Call defineClass into the parent classLoader using the
	 * method.setAccessible(boolean) hack
	 * 
	 * @see ClassLoader#defineClass(String, byte[], int, int)
	 */
	Class defineClass(String name, byte[] bytes) throws ClassFormatError {
		try {
			// Attempt to load the access class in the same loader, which makes
			// protected and default access members accessible.
			Method method = ClassLoader.class.getDeclaredMethod("defineClass", DEF_CLASS_SIG);
			method.setAccessible(true);
			return (Class) method.invoke(getParent(), new Object[] { name, bytes, Integer.valueOf(0), Integer.valueOf(bytes.length) });
		} catch (Exception ignored) {
		}
		return defineClass(name, bytes, 0, bytes.length);
	}
}