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Java example source code file (ClassFinder.java)

This example Java source code file (ClassFinder.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

class, classfinder, classloader, classnotfoundexception, securityexception

The ClassFinder.java Java example source code

/*
 * Copyright (c) 2006, 2012, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */
package com.sun.beans.finder;

import static sun.reflect.misc.ReflectUtil.checkPackageAccess;

/**
 * This is utility class that provides {@code static} methods
 * to find a class with the specified name using the specified class loader.
 *
 * @since 1.7
 *
 * @author Sergey A. Malenkov
 */
public final class ClassFinder {

    /**
     * Returns the {@code Class} object associated
     * with the class or interface with the given string name,
     * using the default class loader.
     * <p>
     * The {@code name} can denote an array class
     * (see {@link Class#getName} for details).
     *
     * @param name  fully qualified name of the desired class
     * @return class object representing the desired class
     *
     * @throws ClassNotFoundException  if the class cannot be located
     *                                 by the specified class loader
     *
     * @see Class#forName(String)
     * @see Class#forName(String,boolean,ClassLoader)
     * @see ClassLoader#getSystemClassLoader()
     * @see Thread#getContextClassLoader()
     */
    public static Class<?> findClass(String name) throws ClassNotFoundException {
        checkPackageAccess(name);
        try {
            ClassLoader loader = Thread.currentThread().getContextClassLoader();
            if (loader == null) {
                // can be null in IE (see 6204697)
                loader = ClassLoader.getSystemClassLoader();
            }
            if (loader != null) {
                return Class.forName(name, false, loader);
            }

        } catch (ClassNotFoundException exception) {
            // use current class loader instead
        } catch (SecurityException exception) {
            // use current class loader instead
        }
        return Class.forName(name);
    }

    /**
     * Returns the {@code Class} object associated with
     * the class or interface with the given string name,
     * using the given class loader.
     * <p>
     * The {@code name} can denote an array class
     * (see {@link Class#getName} for details).
     * <p>
     * If the parameter {@code loader} is null,
     * the class is loaded through the default class loader.
     *
     * @param name    fully qualified name of the desired class
     * @param loader  class loader from which the class must be loaded
     * @return class object representing the desired class
     *
     * @throws ClassNotFoundException  if the class cannot be located
     *                                 by the specified class loader
     *
     * @see #findClass(String,ClassLoader)
     * @see Class#forName(String,boolean,ClassLoader)
     */
    public static Class<?> findClass(String name, ClassLoader loader) throws ClassNotFoundException {
        checkPackageAccess(name);
        if (loader != null) {
            try {
                return Class.forName(name, false, loader);
            } catch (ClassNotFoundException exception) {
                // use default class loader instead
            } catch (SecurityException exception) {
                // use default class loader instead
            }
        }
        return findClass(name);
    }

    /**
     * Returns the {@code Class} object associated
     * with the class or interface with the given string name,
     * using the default class loader.
     * <p>
     * The {@code name} can denote an array class
     * (see {@link Class#getName} for details).
     * <p>
     * This method can be used to obtain
     * any of the {@code Class} objects
     * representing {@code void} or primitive Java types:
     * {@code char}, {@code byte}, {@code short},
     * {@code int}, {@code long}, {@code float},
     * {@code double} and {@code boolean}.
     *
     * @param name  fully qualified name of the desired class
     * @return class object representing the desired class
     *
     * @throws ClassNotFoundException  if the class cannot be located
     *                                 by the specified class loader
     *
     * @see #resolveClass(String,ClassLoader)
     */
    public static Class<?> resolveClass(String name) throws ClassNotFoundException {
        return resolveClass(name, null);
    }

    /**
     * Returns the {@code Class} object associated with
     * the class or interface with the given string name,
     * using the given class loader.
     * <p>
     * The {@code name} can denote an array class
     * (see {@link Class#getName} for details).
     * <p>
     * If the parameter {@code loader} is null,
     * the class is loaded through the default class loader.
     * <p>
     * This method can be used to obtain
     * any of the {@code Class} objects
     * representing {@code void} or primitive Java types:
     * {@code char}, {@code byte}, {@code short},
     * {@code int}, {@code long}, {@code float},
     * {@code double} and {@code boolean}.
     *
     * @param name    fully qualified name of the desired class
     * @param loader  class loader from which the class must be loaded
     * @return class object representing the desired class
     *
     * @throws ClassNotFoundException  if the class cannot be located
     *                                 by the specified class loader
     *
     * @see #findClass(String,ClassLoader)
     * @see PrimitiveTypeMap#getType(String)
     */
    public static Class<?> resolveClass(String name, ClassLoader loader) throws ClassNotFoundException {
        Class<?> type = PrimitiveTypeMap.getType(name);
        return (type == null)
                ? findClass(name, loader)
                : type;
    }

    /**
     * Disable instantiation.
     */
    private ClassFinder() {
    }
}

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