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/*
* Copyright 1999,2005 The Apache Software Foundation.
*
* Licensed 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 javax.servlet;
/**
* Defines an exception that a servlet throws to indicate
* that it is permanently or temporarily unavailable.
*
* <p>When a servlet is permanently unavailable, something is wrong
* with the servlet, and it cannot handle
* requests until some action is taken. For example, the servlet
* might be configured incorrectly, or its state may be corrupted.
* A servlet should log both the error and the corrective action
* that is needed.
*
* <p>A servlet 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 for a period
* of time suggested by the exception, rather than rejecting them until
* the servlet container restarts.
*
*
* @author Various
* @version $Version$
*
*/
public class UnavailableException
extends ServletException {
private Servlet servlet; // what's unavailable
private boolean permanent; // needs admin action?
private int seconds; // unavailability estimate
/**
*
* @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;
}
/**
*
* @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;
}
/**
*
* 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;
}
/**
*
* 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;
}
}