src/share/classes/com/sun/beans/finder/ConstructorFinder.java

/*
 * Copyright (c) 2008, 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 com.sun.beans.WeakCache;

import java.lang.reflect.Constructor;
import java.lang.reflect.Modifier;

/**
 * This utility class provides {@code static} methods
 * to find a public constructor with specified parameter types
 * in specified class.
 *
 * @since 1.7
 *
 * @author Sergey A. Malenkov
 */
public final class ConstructorFinder extends AbstractFinder<Constructor<?>> {
    private static final WeakCache<Signature, Constructor<?>> CACHE = new WeakCache<Signature, Constructor<?>>();

    /**
     * Finds public constructor
     * that is declared in public class.
     *
     * @param type  the class that can have constructor
     * @param args  parameter types that is used to find constructor
     * @return object that represents found constructor
     * @throws NoSuchMethodException if constructor could not be found
     *                               or some constructors are found
     */
    public static Constructor<?> findConstructor(Class<?> type, Class<?>...args) throws NoSuchMethodException {
        if (type.isPrimitive()) {
            throw new NoSuchMethodException("Primitive wrapper does not contain constructors");
        }
        if (type.isInterface()) {
            throw new NoSuchMethodException("Interface does not contain constructors");
        }
        if (Modifier.isAbstract(type.getModifiers())) {
            throw new NoSuchMethodException("Abstract class cannot be instantiated");
        }
        if (!Modifier.isPublic(type.getModifiers())) {
            throw new NoSuchMethodException("Class is not accessible");
        }
        PrimitiveWrapperMap.replacePrimitivesWithWrappers(args);
        Signature signature = new Signature(type, args);

        Constructor<?> constructor = CACHE.get(signature);
        if (constructor != null) {
            return constructor;
        }
        constructor = new ConstructorFinder(args).find(type.getConstructors());
        CACHE.put(signature, constructor);
        return constructor;
    }

    /**
     * Creates constructor finder with specified array of parameter types.
     *
     * @param args  the array of parameter types
     */
    private ConstructorFinder(Class<?>[] args) {
        super(args);
    }

    /**
     * Returns an array of {@code Class} objects
     * that represent the formal parameter types of the constructor
     * Returns an empty array if the constructor takes no parameters.
     *
     * @param constructor  the object that represents constructor
     * @return the parameter types of the constructor
     */
    @Override
    protected Class<?>[] getParameters(Constructor<?> constructor) {
        return constructor.getParameterTypes();
    }

    /**
     * Returns {@code true} if and only if the constructor
     * was declared to take a variable number of arguments.
     *
     * @param constructor  the object that represents constructor
     * @return {@code true} if the constructor was declared
     *         to take a variable number of arguments;
     *         {@code false} otherwise
     */
    @Override
    protected boolean isVarArgs(Constructor<?> constructor) {
        return constructor.isVarArgs();
    }

    /**
     * Checks validness of the constructor.
     * The valid constructor should be public.
     *
     * @param constructor  the object that represents constructor
     * @return {@code true} if the constructor is valid,
     *         {@code false} otherwise
     */
    @Override
    protected boolean isValid(Constructor<?> constructor) {
        return Modifier.isPublic(constructor.getModifiers());
    }
}