jakarta.servlet.UnavailableException Maven / Gradle / Ivy
/*
* Copyright (c) 1997, 2023 Oracle and/or its affiliates and others.
* All rights reserved.
* Copyright 2004 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 jakarta.servlet;
/**
* Defines an exception that a servlet or filter throws to indicate that it is permanently or temporarily unavailable.
*
*
* 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.
*
*
* 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.
*
*
* 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.
*
*
* @author Various
*
*/
public class UnavailableException extends ServletException {
private static final long serialVersionUID = 5622686609215003468L;
private final boolean permanent; // needs admin action?
private int seconds; // unavailability estimate
/**
*
* Constructs a new exception with a descriptive message indicating that the servlet is permanently unavailable.
*
* @param msg a String 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.
*
*
* 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 seconds argument.
*
* @param msg a String 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 boolean 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 true if the servlet is permanently unavailable; false if the servlet is available
* or temporarily unavailable
*
*/
public boolean isPermanent() {
return permanent;
}
/**
* Returns the number of seconds the servlet expects to be temporarily unavailable.
*
*
* 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;
}
}