001/** 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017package org.apache.activemq.thread; 018 019/** 020 * A Valve is a synchronization object used enable or disable the "flow" of 021 * concurrent processing. 022 * 023 * @deprecated 024 */ 025@Deprecated 026public final class Valve { 027 028 private final Object mutex = new Object(); 029 private boolean on; 030 private int turningOff; 031 private int usage; 032 033 public Valve(boolean on) { 034 this.on = on; 035 } 036 037 /** 038 * Turns the valve on. This method blocks until the valve is off. 039 * 040 * @throws InterruptedException if wait is interrupted 041 */ 042 public void turnOn() throws InterruptedException { 043 synchronized (mutex) { 044 while (on) { 045 mutex.wait(); 046 } 047 on = true; 048 mutex.notifyAll(); 049 } 050 } 051 052 public boolean isOn() { 053 synchronized (mutex) { 054 return on; 055 } 056 } 057 058 /** 059 * Turns the valve off. This method blocks until the valve is on and the 060 * valve is not in use. 061 * 062 * @throws InterruptedException if wait is interrupted 063 */ 064 public void turnOff() throws InterruptedException { 065 synchronized (mutex) { 066 if (turningOff < 0) { 067 throw new IllegalStateException("Unbalanced turningOff: " + turningOff); 068 } 069 try { 070 ++turningOff; 071 while (usage > 0 || !on) { 072 mutex.wait(); 073 } 074 on = false; 075 mutex.notifyAll(); 076 } finally { 077 --turningOff; 078 } 079 } 080 } 081 082 /** 083 * Increments the use counter of the valve. This method blocks if the valve 084 * is off, or is being turned off. 085 * 086 * @throws InterruptedException if wait is interrupted 087 */ 088 public void increment() throws InterruptedException { 089 synchronized (mutex) { 090 if (turningOff < 0) { 091 throw new IllegalStateException("Unbalanced turningOff: " + turningOff); 092 } 093 if (usage < 0) { 094 throw new IllegalStateException("Unbalanced usage: " + usage); 095 } 096 // Do we have to wait for the value to be on? 097 while (turningOff > 0 || !on) { 098 mutex.wait(); 099 } 100 usage++; 101 } 102 } 103 104 /** 105 * Decrements the use counter of the valve. 106 */ 107 public void decrement() { 108 synchronized (mutex) { 109 usage--; 110 if (turningOff < 0) { 111 throw new IllegalStateException("Unbalanced turningOff: " + turningOff); 112 } 113 if (usage < 0) { 114 throw new IllegalStateException("Unbalanced usage: " + usage); 115 } 116 if (turningOff > 0 && usage < 1) { 117 mutex.notifyAll(); 118 } 119 } 120 } 121 122}