Quelle UnavailableException.java Sprache: JAVA

/*
* 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 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.
*/
public class UnavailableException extends ServletException {

 private static final long serialVersionUID = 1L;

 /**
 * Is the issue permanent - i.e. is administrator action required?
 */
 private final boolean permanent;

 /**
 * The estimate of how long the Servlet will be unavailable.
 */
 private final int seconds;

 /**
 * 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);
 seconds = 0;
 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 <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;
 }

 /**
 * 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;
 }
}

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