/*
 * 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.
 */

//
// This source code implements specifications defined by the Java
// Community Process. In order to remain compliant with the specification
// DO NOT add / change / or delete method signatures!
//

package javax.servlet;

/**
 * Defines an exception that a servlet or filter throws to indicate
 * that it is permanently or temporarily unavailable.
 *
 * <p>When a servlet or filter is permanently unavailable, something is wrong
 * with it, and it cannot handle
 * requests until some action is taken. For example, a servlet
 * might be configured incorrectly, or a filter's state may be corrupted.
 * The component should log both the error and the corrective action
 * that is needed.
 *
 * <p>A servlet or filter is temporarily unavailable if it cannot handle
 * requests momentarily due to some system-wide problem. For example,
 * a third-tier server might not be accessible, or there may be
 * insufficient memory or disk storage to handle requests. A system
 * administrator may need to take corrective action.
 *
 * <p>Servlet containers can safely treat both types of unavailable
 * exceptions in the same way. However, treating temporary unavailability
 * effectively makes the servlet container more robust. Specifically,
 * the servlet container might block requests to the servlet or filter for a period
 * of time suggested by the exception, rather than rejecting them until
 * the servlet container restarts.
 *
 * @version $Rev: 467553 $ $Date: 2006-10-25 06:01:51 +0200 (Wed, 25 Oct 2006) $
 */
public class UnavailableException extends ServletException {
    /**
     * What is unavailable
     */
    private Servlet servlet;
    /**
     * Does this need an admin action?
     */
    private boolean permanent;
    /**
     * Estimate of how long the resource will be unavaile.
     */
    private int seconds;

    /**
     * @deprecated As of Java Servlet API 2.2, use {@link
     * #UnavailableException(String)} instead.
     *
     * @param servlet the <code>Servlet</code> instance that is unavailable
     *
     * @param msg a <code>String</code> specifying the descriptive message
     */
    public UnavailableException(Servlet servlet, String msg) {
        super(msg);
        this.servlet = servlet;
        permanent = true;
    }

    /**
     * @deprecated As of Java Servlet API 2.2, use {@link
     * #UnavailableException(String, int)} instead.
     *
     * @param seconds an integer specifying the number of seconds
     * the servlet expects to be unavailable; if zero or negative,
     * indicates that the servlet can't make an estimate
     *
     * @param servlet the <code>Servlet</code> that is unavailable
     *
     * @param msg a <code>String</code> specifying the descriptive
     * message, which can be written to a log file or displayed for
     * the user.
     */
    public UnavailableException(int seconds, Servlet servlet, String msg) {
        super(msg);
        this.servlet = servlet;
        if (seconds <= 0) {
            this.seconds = -1;
        } else {
            this.seconds = seconds;
        }
        permanent = false;
    }

    /**
     * Constructs a new exception with a descriptive
     * message indicating that the servlet is permanently
     * unavailable.
     *
     * @param msg a <code>String</code> specifying the descriptive message
     */
    public UnavailableException(String msg) {
        super(msg);

        permanent = true;
    }

    /**
     * Constructs a new exception with a descriptive message
     * indicating that the servlet is temporarily unavailable
     * and giving an estimate of how long it will be unavailable.
     *
     * <p>In some cases, the servlet cannot make an estimate. For
     * example, the servlet might know that a server it needs is
     * not running, but not be able to report how long it will take
     * to be restored to functionality. This can be indicated with
     * a negative or zero value for the <code>seconds</code> argument.
     *
     * @param msg a <code>String</code> specifying the descriptive
     * message, which can be written to a log file or displayed for
     * the user.
     *
     * @param seconds an integer specifying the number of seconds
     * the servlet expects to be unavailable; if zero or negative,
     * indicates that the servlet can't make an estimate
     */
    public UnavailableException(String msg, int seconds) {
        super(msg);

        if (seconds <= 0) {
            this.seconds = -1;
        } else {
            this.seconds = seconds;
        }
        permanent = false;
    }

    /**
     * Returns a <code>boolean</code> indicating
     * whether the servlet is permanently unavailable.
     * If so, something is wrong with the servlet, and the
     * system administrator must take some corrective action.
     *
     * @return <code>true</code> if the servlet is
     * permanently unavailable; <code>false</code>
     * if the servlet is available or temporarily unavailable
     */
    public boolean isPermanent() {
        return permanent;
    }

    /**
     * @deprecated As of Java Servlet API 2.2, with no replacement.
     *
     * Returns the servlet that is reporting its unavailability.
     *
     * @return the <code>Servlet</code> object that is
     * throwing the <code>UnavailableException</code>
     */
    public Servlet getServlet() {
        return servlet;
    }

    /**
     * Returns the number of seconds the servlet expects to
     * be temporarily unavailable.
     *
     * <p>If this method returns a negative number, the servlet
     * is permanently unavailable or cannot provide an estimate of
     * how long it will be unavailable. No effort is
     * made to correct for the time elapsed since the exception was
     * first reported.
     *
     * @return an integer specifying the number of seconds
     * the servlet will be temporarily unavailable, or a negative
     * number if the servlet is permanently unavailable or cannot
     * make an estimate
     */
    public int getUnavailableSeconds() {
        return permanent ? -1 : seconds;
    }
}
