179 lines
6.9 KiB
Java
179 lines
6.9 KiB
Java
/*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership.
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* The ASF licenses this file to You under the Apache License, Version 2.0
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* (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package javax.servlet;
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/**
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* Defines an exception that a servlet or filter throws to indicate that it is
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* permanently or temporarily unavailable.
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* <p>
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* When a servlet or filter is permanently unavailable, something is wrong with
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* it, and it cannot handle requests until some action is taken. For example, a
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* servlet might be configured incorrectly, or a filter's state may be
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* corrupted. The component should log both the error and the corrective action
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* that is needed.
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* <p>
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* A servlet or filter is temporarily unavailable if it cannot handle requests
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* momentarily due to some system-wide problem. For example, a third-tier server
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* might not be accessible, or there may be insufficient memory or disk storage
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* to handle requests. A system administrator may need to take corrective
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* action.
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* <p>
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* Servlet containers can safely treat both types of unavailable exceptions in
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* the same way. However, treating temporary unavailability effectively makes
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* the servlet container more robust. Specifically, the servlet container might
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* block requests to the servlet or filter for a period of time suggested by the
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* exception, rather than rejecting them until the servlet container restarts.
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*/
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public class UnavailableException extends ServletException {
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private static final long serialVersionUID = 1L;
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private final Servlet servlet; // what's unavailable
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private final boolean permanent; // needs admin action?
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private final int seconds; // unavailability estimate
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/**
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* @param servlet
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* the <code>Servlet</code> instance that is unavailable
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* @param msg
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* a <code>String</code> specifying the descriptive message
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* @deprecated As of Java Servlet API 2.2, use
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* {@link #UnavailableException(String)} instead.
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*/
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@SuppressWarnings("dep-ann")
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// Spec API does not use @Deprecated
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public UnavailableException(Servlet servlet, String msg) {
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super(msg);
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this.servlet = servlet;
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permanent = true;
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this.seconds = 0;
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}
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/**
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* @param seconds
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* an integer specifying the number of seconds the servlet
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* expects to be unavailable; if zero or negative, indicates that
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* the servlet can't make an estimate
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* @param servlet
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* the <code>Servlet</code> that is unavailable
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* @param msg
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* a <code>String</code> specifying the descriptive message,
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* which can be written to a log file or displayed for the user.
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* @deprecated As of Java Servlet API 2.2, use
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* {@link #UnavailableException(String, int)} instead.
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*/
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@SuppressWarnings("dep-ann")
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// Spec API does not use @Deprecated
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public UnavailableException(int seconds, Servlet servlet, String msg) {
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super(msg);
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this.servlet = servlet;
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if (seconds <= 0)
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this.seconds = -1;
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else
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this.seconds = seconds;
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permanent = false;
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}
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/**
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* Constructs a new exception with a descriptive message indicating that the
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* servlet is permanently unavailable.
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*
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* @param msg
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* a <code>String</code> specifying the descriptive message
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*/
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public UnavailableException(String msg) {
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super(msg);
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seconds = 0;
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servlet = null;
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permanent = true;
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}
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/**
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* Constructs a new exception with a descriptive message indicating that the
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* servlet is temporarily unavailable and giving an estimate of how long it
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* will be unavailable.
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* <p>
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* In some cases, the servlet cannot make an estimate. For example, the
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* servlet might know that a server it needs is not running, but not be able
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* to report how long it will take to be restored to functionality. This can
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* be indicated with a negative or zero value for the <code>seconds</code>
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* argument.
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*
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* @param msg
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* a <code>String</code> specifying the descriptive message,
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* which can be written to a log file or displayed for the user.
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* @param seconds
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* an integer specifying the number of seconds the servlet
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* expects to be unavailable; if zero or negative, indicates that
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* the servlet can't make an estimate
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*/
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public UnavailableException(String msg, int seconds) {
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super(msg);
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if (seconds <= 0)
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this.seconds = -1;
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else
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this.seconds = seconds;
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servlet = null;
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permanent = false;
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}
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/**
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* Returns a <code>boolean</code> indicating whether the servlet is
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* permanently unavailable. If so, something is wrong with the servlet, and
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* the system administrator must take some corrective action.
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*
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* @return <code>true</code> if the servlet is permanently unavailable;
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* <code>false</code> if the servlet is available or temporarily
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* unavailable
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*/
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public boolean isPermanent() {
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return permanent;
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}
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/**
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* Returns the servlet that is reporting its unavailability.
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*
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* @return the <code>Servlet</code> object that is throwing the
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* <code>UnavailableException</code>
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* @deprecated As of Java Servlet API 2.2, with no replacement.
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*/
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@SuppressWarnings("dep-ann")
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// Spec API does not use @Deprecated
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public Servlet getServlet() {
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return servlet;
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}
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/**
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* Returns the number of seconds the servlet expects to be temporarily
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* unavailable.
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* <p>
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* If this method returns a negative number, the servlet is permanently
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* unavailable or cannot provide an estimate of how long it will be
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* unavailable. No effort is made to correct for the time elapsed since the
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* exception was first reported.
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*
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* @return an integer specifying the number of seconds the servlet will be
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* temporarily unavailable, or a negative number if the servlet is
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* permanently unavailable or cannot make an estimate
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*/
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public int getUnavailableSeconds() {
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return permanent ? -1 : seconds;
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}
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}
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