/*
 *  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.tomcat;

/**
 * Defines methods for binding and unbinding the current thread's context class loader to a web application class
 * loader.
 */
public interface ContextBind {

    /**
     * Change the current thread context class loader to the web application class loader. If no web application class
     * loader is defined, or if the current thread is already using the web application class loader then no change will
     * be made. If the class loader is changed and a {@link org.apache.catalina.ThreadBindingListener} is configured
     * then {@link org.apache.catalina.ThreadBindingListener#bind()} will be called after the change has been made.
     *
     * @param usePrivilegedAction Should a {@link java.security.PrivilegedAction} be used when obtaining the current
     *                                thread context class loader and setting the new one?
     * @param originalClassLoader The current class loader if known to save this method having to look it up
     *
     * @return If the class loader has been changed by the method it will return the thread context class loader in use
     *             when the method was called. If no change was made then this method returns null.
     */
    ClassLoader bind(boolean usePrivilegedAction, ClassLoader originalClassLoader);

    /**
     * Restore the current thread context class loader to the original class loader in used before
     * {@link #bind(boolean, ClassLoader)} was called. If no original class loader is passed to this method then no
     * change will be made. If the class loader is changed and a {@link org.apache.catalina.ThreadBindingListener} is
     * configured then {@link org.apache.catalina.ThreadBindingListener#unbind()} will be called before the change is
     * made.
     *
     * @param usePrivilegedAction Should a {@link java.security.PrivilegedAction} be used when setting the current
     *                                thread context class loader?
     * @param originalClassLoader The class loader to restore as the thread context class loader
     */
    void unbind(boolean usePrivilegedAction, ClassLoader originalClassLoader);
}
