src/main/java/org/apache/commons/jxpath/util/ClassLoaderUtil.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.commons.jxpath.util;

import java.util.HashMap;
import java.util.Map;

/**
 * Port of class loading methods from <code>org.apache.commons.lang.ClassUtils</code> from
 * the Apache Commons Lang Component. Some adjustments made to remove dependency on
 * <code>org.apache.commons.lang.StringUtils</code>. Also modified to fall back on the
 * current class loader when an attempt to load a class with the context class loader
 * results in a <code>java.lang.ClassNotFoundException</code>.
 *
 * @see org.apache.commons.lang.ClassUtils
 *
 * @author Stephen Colebourne
 * @author Gary Gregory
 * @author Norm Deane
 * @author Alban Peignier
 * @author Tomasz Blachowicz
 * @author John Trimble
 */
public class ClassLoaderUtil {
    /**
     * Maps a primitive class name to its corresponding abbreviation used in array class names.
     */
    private static Map abbreviationMap = new HashMap();

    /**
     * Add primitive type abbreviation to maps of abbreviations.
     *
     * @param primitive Canonical name of primitive type
     * @param abbreviation Corresponding abbreviation of primitive type
     */
    private static void addAbbreviation(String primitive, String abbreviation) {
        abbreviationMap.put(primitive, abbreviation);
    }

    /**
     * Feed abbreviation maps
     */
    static {
        addAbbreviation("int", "I");
        addAbbreviation("boolean", "Z");
        addAbbreviation("float", "F");
        addAbbreviation("long", "J");
        addAbbreviation("short", "S");
        addAbbreviation("byte", "B");
        addAbbreviation("double", "D");
        addAbbreviation("char", "C");
    }

    // Class loading
    // ----------------------------------------------------------------------
    /**
     * Returns the class represented by <code>className</code> using the
     * <code>classLoader</code>.  This implementation supports names like
     * "<code>java.lang.String[]</code>" as well as "<code>[Ljava.lang.String;</code>".
     *
     * @param classLoader  the class loader to use to load the class
     * @param className  the class name
     * @param initialize  whether the class must be initialized
     * @return the class represented by <code>className</code> using the <code>classLoader</code>
     * @throws ClassNotFoundException if the class is not found
     */
    public static Class getClass(ClassLoader classLoader, String className, boolean initialize)
        throws ClassNotFoundException {
        Class clazz;
        if (abbreviationMap.containsKey(className)) {
            String clsName = "[" + abbreviationMap.get(className);
            clazz = Class.forName(clsName, initialize, classLoader).getComponentType();
        }
        else {
            clazz = Class.forName(toCanonicalName(className), initialize, classLoader);
        }
        return clazz;
    }

    /**
     * Returns the (initialized) class represented by <code>className</code>
     * using the <code>classLoader</code>.  This implementation supports names
     * like "<code>java.lang.String[]</code>" as well as
     * "<code>[Ljava.lang.String;</code>".
     *
     * @param classLoader  the class loader to use to load the class
     * @param className  the class name
     * @return the class represented by <code>className</code> using the <code>classLoader</code>
     * @throws ClassNotFoundException if the class is not found
     */
    public static Class getClass(ClassLoader classLoader, String className) throws ClassNotFoundException {
        return getClass(classLoader, className, true);
    }

    /**
     * Returns the (initialized) class represented by <code>className</code>
     * using the current thread's context class loader. This implementation
     * supports names like "<code>java.lang.String[]</code>" as well as
     * "<code>[Ljava.lang.String;</code>".
     *
     * @param className  the class name
     * @return the class represented by <code>className</code> using the current thread's context class loader
     * @throws ClassNotFoundException if the class is not found
     */
    public static Class getClass(String className) throws ClassNotFoundException {
        return getClass(className, true);
    }

    /**
     * Returns the class represented by <code>className</code> using the
     * current thread's context class loader. This implementation supports
     * names like "<code>java.lang.String[]</code>" as well as
     * "<code>[Ljava.lang.String;</code>".
     *
     * @param className  the class name
     * @param initialize  whether the class must be initialized
     * @return the class represented by <code>className</code> using the current thread's context class loader
     * @throws ClassNotFoundException if the class is not found
     */
    public static Class getClass(String className, boolean initialize) throws ClassNotFoundException {
        ClassLoader contextCL = Thread.currentThread().getContextClassLoader();
        ClassLoader currentCL = ClassLoaderUtil.class.getClassLoader();
        if (contextCL != null) {
            try {
                return getClass(contextCL, className, initialize);
            }
            catch (ClassNotFoundException e) {//NOPMD
                // ignore this exception and try the current class loader.
            }
        }
        return getClass(currentCL, className, initialize);
    }

    /**
     * Converts a class name to a JLS style class name.
     *
     * @param className  the class name
     * @return the converted name
     */
    private static String toCanonicalName(String className) {
        if (className == null) {
            throw new RuntimeException("Argument className was null.");
        }
        else if (className.endsWith("[]")) {
            StringBuffer classNameBuffer = new StringBuffer();
            while (className.endsWith("[]")) {
                className = className.substring(0, className.length() - 2);
                classNameBuffer.append("[");
            }
            String abbreviation = (String) abbreviationMap.get(className);
            if (abbreviation != null) {
                classNameBuffer.append(abbreviation);
            }
            else {
                classNameBuffer.append("L").append(className).append(";");
            }
            className = classNameBuffer.toString();
        }
        return className;
    }
}