    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *      http://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 * Unless required by applicable law or agreed to in writing, software
    012 * distributed under the License is distributed on an "AS IS" BASIS,
    013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 * See the License for the specific language governing permissions and
    015 * limitations under the License.
    016 */
    017
    018package org.apache.commons.jxpath.util;
    019
    020import java.util.HashMap;
    021import java.util.Map;
    022import java.util.Objects;
    023
    024/**
    025 * Port of class loading methods from {@code org.apache.commons.lang3.ClassUtils} from the Apache Commons Lang Component. Some adjustments made to remove
    026 * dependency on {@code org.apache.commons.lang3.StringUtils}. Also modified to fall back on the current class loader when an attempt to load a class with the
    027 * context class loader results in a {@code java.lang.ClassNotFoundException}.
    028 *
    029 * See org.apache.commons.lang3.ClassUtils
    030 * @since 1.4.0
    031 */
    032public final class ClassLoaderUtil {
    033
    034    /**
    035     * Maps a primitive class name to its corresponding abbreviation used in array class names.
    036     */
    037    private static Map<String, String> abbreviationMap = new HashMap<>();
    038    /**
    039     * Feed abbreviation maps
    040     */
    041    static {
    042        addAbbreviation("int", "I");
    043        addAbbreviation("boolean", "Z");
    044        addAbbreviation("float", "F");
    045        addAbbreviation("long", "J");
    046        addAbbreviation("short", "S");
    047        addAbbreviation("byte", "B");
    048        addAbbreviation("double", "D");
    049        addAbbreviation("char", "C");
    050    }
    051
    052    /**
    053     * Adds primitive type abbreviation to map of abbreviations.
    054     *
    055     * @param primitive    Canonical name of primitive type
    056     * @param abbreviation Corresponding abbreviation of primitive type
    057     */
    058    private static void addAbbreviation(final String primitive, final String abbreviation) {
    059        abbreviationMap.put(primitive, abbreviation);
    060    }
    061
    062    /**
    063     * Gets the class represented by {@code className} using the {@code classLoader}. This implementation supports names like "{@code java.lang.String[]}" as
    064     * well as "{@code [Ljava.lang.String;}".
    065     *
    066     * @param <T> The expected class type.
    067     * @param classLoader the class loader to use to load the class
    068     * @param className   the class name
    069     * @param initialize  whether the class must be initialized
    070     * @return the class represented by {@code className} using the {@code classLoader}
    071     * @throws ClassNotFoundException if the class is not found
    072     */
    073    @SuppressWarnings("unchecked") // assume the call site knows what it's doing.
    074    private static <T> Class<T> getClass(final ClassLoader classLoader, final String className, final boolean initialize) throws ClassNotFoundException {
    075        Class<T> clazz;
    076        if (abbreviationMap.containsKey(className)) {
    077            final String clsName = "[" + abbreviationMap.get(className);
    078            clazz = (Class<T>) Class.forName(clsName, initialize, classLoader).getComponentType();
    079        } else {
    080            clazz = (Class<T>) Class.forName(toCanonicalName(className), initialize, classLoader);
    081        }
    082        return clazz;
    083    }
    084
    085    /**
    086     * Gets the class represented by {@code className} using the current thread's context class loader. This implementation supports names like
    087     * "{@code java.lang.String[]}" as well as "{@code [Ljava.lang.String;}".
    088     *
    089     * @param <T> The expected class type.
    090     * @param className  the class name
    091     * @param initialize whether the class must be initialized
    092     * @return the class represented by {@code className} using the current thread's context class loader
    093     * @throws ClassNotFoundException if the class is not found
    094     */
    095    public static <T> Class<T> getClass(final String className, final boolean initialize) throws ClassNotFoundException {
    096        final ClassLoader contextCL = Thread.currentThread().getContextClassLoader();
    097        final ClassLoader currentCL = ClassLoaderUtil.class.getClassLoader();
    098        if (contextCL != null) {
    099            try {
    100                return getClass(contextCL, className, initialize);
    101            } catch (final ClassNotFoundException ignore) { // NOPMD
    102                // ignore this exception and try the current class loader
    103            }
    104        }
    105        return getClass(currentCL, className, initialize);
    106    }
    107
    108    /**
    109     * Converts a class name to a JLS style class name.
    110     *
    111     * @param className the class name
    112     * @return the converted name
    113     */
    114    private static String toCanonicalName(String className) {
    115        Objects.requireNonNull(className, "className");
    116        if (className.endsWith("[]")) {
    117            final StringBuilder classNameBuffer = new StringBuilder();
    118            while (className.endsWith("[]")) {
    119                className = className.substring(0, className.length() - 2);
    120                classNameBuffer.append("[");
    121            }
    122            final String abbreviation = abbreviationMap.get(className);
    123            if (abbreviation != null) {
    124                classNameBuffer.append(abbreviation);
    125            } else {
    126                classNameBuffer.append("L").append(className).append(";");
    127            }
    128            className = classNameBuffer.toString();
    129        }
    130        return className;
    131    }
    132
    133    /**
    134     * New need to constructs new instances.
    135     */
    136    private ClassLoaderUtil() {
    137        // empty
    138    }
    139}