001package org.eclipse.aether.named.support; 002 003/* 004 * Licensed to the Apache Software Foundation (ASF) under one 005 * or more contributor license agreements. See the NOTICE file 006 * distributed with this work for additional information 007 * regarding copyright ownership. The ASF licenses this file 008 * to you under the Apache License, Version 2.0 (the 009 * "License"); you may not use this file except in compliance 010 * with the License. You may obtain a copy of the License at 011 * 012 * http://www.apache.org/licenses/LICENSE-2.0 013 * 014 * Unless required by applicable law or agreed to in writing, 015 * software distributed under the License is distributed on an 016 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY 017 * KIND, either express or implied. See the License for the 018 * specific language governing permissions and limitations 019 * under the License. 020 */ 021 022import org.eclipse.aether.named.NamedLockFactory; 023import org.slf4j.Logger; 024import org.slf4j.LoggerFactory; 025 026import java.util.Objects; 027import java.util.concurrent.ConcurrentHashMap; 028import java.util.concurrent.ConcurrentMap; 029import java.util.concurrent.atomic.AtomicInteger; 030 031/** 032 * Support class for {@link NamedLockFactory} implementations providing reference counting. 033 */ 034public abstract class NamedLockFactorySupport 035 implements NamedLockFactory 036{ 037 protected final Logger logger = LoggerFactory.getLogger( getClass() ); 038 039 private final ConcurrentMap<String, NamedLockHolder> locks; 040 041 public NamedLockFactorySupport() 042 { 043 this.locks = new ConcurrentHashMap<>(); 044 } 045 046 @Override 047 public NamedLockSupport getLock( final String name ) 048 { 049 return locks.compute( name, ( k, v ) -> 050 { 051 if ( v == null ) 052 { 053 v = new NamedLockHolder( createLock( k ) ); 054 } 055 v.incRef(); 056 return v; 057 } ).namedLock; 058 } 059 060 @Override 061 public void shutdown() 062 { 063 // override if needed 064 } 065 066 public void closeLock( final String name ) 067 { 068 locks.compute( name, ( k, v ) -> 069 { 070 if ( v != null && v.decRef() == 0 ) 071 { 072 destroyLock( v.namedLock.name() ); 073 return null; 074 } 075 return v; 076 } ); 077 } 078 079 080 @Override 081 protected void finalize() throws Throwable 082 { 083 try 084 { 085 if ( !locks.isEmpty() ) 086 { 087 // report leak 088 logger.warn( "Lock leak, referenced locks still exist {}", locks ); 089 } 090 } 091 finally 092 { 093 super.finalize(); 094 } 095 } 096 097 /** 098 * Implementations shall create and return {@link NamedLockSupport} for given {@code name}, this method must never 099 * return {@code null}. 100 */ 101 protected abstract NamedLockSupport createLock( final String name ); 102 103 /** 104 * Implementation may override this (empty) method to perform some sort of implementation specific cleanup for 105 * given lock name. Invoked when reference count for given name drops to zero and named lock was removed. 106 */ 107 protected void destroyLock( final String name ) 108 { 109 // override if needed 110 } 111 112 private static final class NamedLockHolder 113 { 114 private final NamedLockSupport namedLock; 115 116 private final AtomicInteger referenceCount; 117 118 private NamedLockHolder( final NamedLockSupport namedLock ) 119 { 120 this.namedLock = Objects.requireNonNull( namedLock ); 121 this.referenceCount = new AtomicInteger( 0 ); 122 } 123 124 private int incRef() 125 { 126 return referenceCount.incrementAndGet(); 127 } 128 129 private int decRef() 130 { 131 return referenceCount.decrementAndGet(); 132 } 133 134 @Override 135 public String toString() 136 { 137 return "[refCount=" + referenceCount.get() + ", lock=" + namedLock + "]"; 138 } 139 } 140}