/*
 * 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.jasper.servlet;

import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.net.URLClassLoader;

/**
 * Class loader for loading servlet class files (corresponding to JSP files) and tag handler class files (corresponding
 * to tag files).
 */
public class JasperLoader extends URLClassLoader {

    private final String packageName;

    /**
     * Constructs a new JasperLoader.
     *
     * @param urls the URLs to load classes from
     * @param parent the parent class loader
     * @param packageName the package name
     */
    public JasperLoader(URL[] urls, ClassLoader parent, String packageName) {
        super(urls, parent);
        this.packageName = packageName;
    }

    /**
     * Load the class with the specified name. This method searches for classes in the same manner as
     * <code>loadClass(String, boolean)</code> with <code>false</code> as the second argument.
     *
     * @param name Name of the class to be loaded
     *
     * @exception ClassNotFoundException if the class was not found
     */
    @Override
    public Class<?> loadClass(String name) throws ClassNotFoundException {
        return loadClass(name, false);
    }

    /**
     * Load the class with the specified name, searching using the following algorithm until it finds and returns the
     * class. If the class cannot be found, returns <code>ClassNotFoundException</code>.
     * <ul>
     * <li>Call <code>findLoadedClass(String)</code> to check if the class has already been loaded. If it has, the same
     * <code>Class</code> object is returned.</li>
     * <li>If the <code>delegate</code> property is set to <code>true</code>, call the <code>loadClass()</code> method
     * of the parent class loader, if any.</li>
     * <li>Call <code>findClass()</code> to find this class in our locally defined repositories.</li>
     * <li>Call the <code>loadClass()</code> method of our parent class loader, if any.</li>
     * </ul>
     * If the class was found using the above steps, and the <code>resolve</code> flag is <code>true</code>, this method
     * will then call <code>resolveClass(Class)</code> on the resulting Class object.
     *
     * @param name    Name of the class to be loaded
     * @param resolve If <code>true</code> then resolve the class
     *
     * @exception ClassNotFoundException if the class was not found
     */
    @Override
    public synchronized Class<?> loadClass(final String name, boolean resolve) throws ClassNotFoundException {

        Class<?> clazz;

        // (0) Check our previously loaded class cache
        clazz = findLoadedClass(name);
        if (clazz != null) {
            if (resolve) {
                resolveClass(clazz);
            }
            return clazz;
        }

        if (!name.startsWith(packageName + '.')) {
            // Class is not in org.apache.jsp, therefore, have our
            // parent load it
            clazz = getParent().loadClass(name);
            if (resolve) {
                resolveClass(clazz);
            }
            return clazz;
        }

        return findClass(name);
    }


    /**
     * Delegate to parent
     *
     * @see java.lang.ClassLoader#getResourceAsStream(String)
     */
    @Override
    public InputStream getResourceAsStream(String name) {
        InputStream is = getParent().getResourceAsStream(name);
        if (is == null) {
            URL url = findResource(name);
            if (url != null) {
                try {
                    is = url.openStream();
                } catch (IOException ignore) {
                    // Ignore
                }
            }
        }
        return is;
    }
}