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| <pre><span class="sourceLineNo">001</span><a id="line.1">/*</a> |
| <span class="sourceLineNo">002</span><a id="line.2"> * Licensed to the Apache Software Foundation (ASF) under one</a> |
| <span class="sourceLineNo">003</span><a id="line.3"> * or more contributor license agreements. See the NOTICE file</a> |
| <span class="sourceLineNo">004</span><a id="line.4"> * distributed with this work for additional information</a> |
| <span class="sourceLineNo">005</span><a id="line.5"> * regarding copyright ownership. The ASF licenses this file</a> |
| <span class="sourceLineNo">006</span><a id="line.6"> * to you under the Apache License, Version 2.0 (the</a> |
| <span class="sourceLineNo">007</span><a id="line.7"> * "License"); you may not use this file except in compliance</a> |
| <span class="sourceLineNo">008</span><a id="line.8"> * with the License. You may obtain a copy of the License at</a> |
| <span class="sourceLineNo">009</span><a id="line.9"> *</a> |
| <span class="sourceLineNo">010</span><a id="line.10"> * http://www.apache.org/licenses/LICENSE-2.0</a> |
| <span class="sourceLineNo">011</span><a id="line.11"> *</a> |
| <span class="sourceLineNo">012</span><a id="line.12"> * Unless required by applicable law or agreed to in writing,</a> |
| <span class="sourceLineNo">013</span><a id="line.13"> * software distributed under the License is distributed on an</a> |
| <span class="sourceLineNo">014</span><a id="line.14"> * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY</a> |
| <span class="sourceLineNo">015</span><a id="line.15"> * KIND, either express or implied. See the License for the</a> |
| <span class="sourceLineNo">016</span><a id="line.16"> * specific language governing permissions and limitations</a> |
| <span class="sourceLineNo">017</span><a id="line.17"> * under the License.</a> |
| <span class="sourceLineNo">018</span><a id="line.18"> */</a> |
| <span class="sourceLineNo">019</span><a id="line.19">package org.apache.shiro.util;</a> |
| <span class="sourceLineNo">020</span><a id="line.20"></a> |
| <span class="sourceLineNo">021</span><a id="line.21">import java.lang.ref.ReferenceQueue;</a> |
| <span class="sourceLineNo">022</span><a id="line.22">import java.lang.ref.SoftReference;</a> |
| <span class="sourceLineNo">023</span><a id="line.23">import java.util.*;</a> |
| <span class="sourceLineNo">024</span><a id="line.24">import java.util.concurrent.ConcurrentHashMap;</a> |
| <span class="sourceLineNo">025</span><a id="line.25">import java.util.concurrent.ConcurrentLinkedQueue;</a> |
| <span class="sourceLineNo">026</span><a id="line.26">import java.util.concurrent.locks.ReentrantLock;</a> |
| <span class="sourceLineNo">027</span><a id="line.27"></a> |
| <span class="sourceLineNo">028</span><a id="line.28"></a> |
| <span class="sourceLineNo">029</span><a id="line.29">/**</a> |
| <span class="sourceLineNo">030</span><a id="line.30"> * A <code><em>Soft</em>HashMap</code> is a memory-constrained map that stores its <em>values</em> in</a> |
| <span class="sourceLineNo">031</span><a id="line.31"> * {@link SoftReference SoftReference}s. (Contrast this with the JDK's</a> |
| <span class="sourceLineNo">032</span><a id="line.32"> * {@link WeakHashMap WeakHashMap}, which uses weak references for its <em>keys</em>, which is of little value if you</a> |
| <span class="sourceLineNo">033</span><a id="line.33"> * want the cache to auto-resize itself based on memory constraints).</a> |
| <span class="sourceLineNo">034</span><a id="line.34"> * <p/></a> |
| <span class="sourceLineNo">035</span><a id="line.35"> * Having the values wrapped by soft references allows the cache to automatically reduce its size based on memory</a> |
| <span class="sourceLineNo">036</span><a id="line.36"> * limitations and garbage collection. This ensures that the cache will not cause memory leaks by holding strong</a> |
| <span class="sourceLineNo">037</span><a id="line.37"> * references to all of its values.</a> |
| <span class="sourceLineNo">038</span><a id="line.38"> * <p/></a> |
| <span class="sourceLineNo">039</span><a id="line.39"> * This class is a generics-enabled Map based on initial ideas from Heinz Kabutz's and Sydney Redelinghuys's</a> |
| <span class="sourceLineNo">040</span><a id="line.40"> * <a href="http://www.javaspecialists.eu/archive/Issue015.html">publicly posted version (with their approval)</a>, with</a> |
| <span class="sourceLineNo">041</span><a id="line.41"> * continued modifications.</a> |
| <span class="sourceLineNo">042</span><a id="line.42"> * <p/></a> |
| <span class="sourceLineNo">043</span><a id="line.43"> * This implementation is thread-safe and usable in concurrent environments.</a> |
| <span class="sourceLineNo">044</span><a id="line.44"> *</a> |
| <span class="sourceLineNo">045</span><a id="line.45"> * @since 1.0</a> |
| <span class="sourceLineNo">046</span><a id="line.46"> */</a> |
| <span class="sourceLineNo">047</span><a id="line.47">public class SoftHashMap<K, V> implements Map<K, V> {</a> |
| <span class="sourceLineNo">048</span><a id="line.48"></a> |
| <span class="sourceLineNo">049</span><a id="line.49"> /**</a> |
| <span class="sourceLineNo">050</span><a id="line.50"> * The default value of the RETENTION_SIZE attribute, equal to 100.</a> |
| <span class="sourceLineNo">051</span><a id="line.51"> */</a> |
| <span class="sourceLineNo">052</span><a id="line.52"> private static final int DEFAULT_RETENTION_SIZE = 100;</a> |
| <span class="sourceLineNo">053</span><a id="line.53"></a> |
| <span class="sourceLineNo">054</span><a id="line.54"> /**</a> |
| <span class="sourceLineNo">055</span><a id="line.55"> * The internal HashMap that will hold the SoftReference.</a> |
| <span class="sourceLineNo">056</span><a id="line.56"> */</a> |
| <span class="sourceLineNo">057</span><a id="line.57"> private final Map<K, SoftValue<V, K>> map;</a> |
| <span class="sourceLineNo">058</span><a id="line.58"></a> |
| <span class="sourceLineNo">059</span><a id="line.59"> /**</a> |
| <span class="sourceLineNo">060</span><a id="line.60"> * The number of strong references to hold internally, that is, the number of instances to prevent</a> |
| <span class="sourceLineNo">061</span><a id="line.61"> * from being garbage collected automatically (unlike other soft references).</a> |
| <span class="sourceLineNo">062</span><a id="line.62"> */</a> |
| <span class="sourceLineNo">063</span><a id="line.63"> private final int RETENTION_SIZE;</a> |
| <span class="sourceLineNo">064</span><a id="line.64"></a> |
| <span class="sourceLineNo">065</span><a id="line.65"> /**</a> |
| <span class="sourceLineNo">066</span><a id="line.66"> * The FIFO list of strong references (not to be garbage collected), order of last access.</a> |
| <span class="sourceLineNo">067</span><a id="line.67"> */</a> |
| <span class="sourceLineNo">068</span><a id="line.68"> private final Queue<V> strongReferences; //guarded by 'strongReferencesLock'</a> |
| <span class="sourceLineNo">069</span><a id="line.69"> private final ReentrantLock strongReferencesLock;</a> |
| <span class="sourceLineNo">070</span><a id="line.70"></a> |
| <span class="sourceLineNo">071</span><a id="line.71"> /**</a> |
| <span class="sourceLineNo">072</span><a id="line.72"> * Reference queue for cleared SoftReference objects.</a> |
| <span class="sourceLineNo">073</span><a id="line.73"> */</a> |
| <span class="sourceLineNo">074</span><a id="line.74"> private final ReferenceQueue<? super V> queue;</a> |
| <span class="sourceLineNo">075</span><a id="line.75"></a> |
| <span class="sourceLineNo">076</span><a id="line.76"> /**</a> |
| <span class="sourceLineNo">077</span><a id="line.77"> * Creates a new SoftHashMap with a default retention size size of</a> |
| <span class="sourceLineNo">078</span><a id="line.78"> * {@link #DEFAULT_RETENTION_SIZE DEFAULT_RETENTION_SIZE} (100 entries).</a> |
| <span class="sourceLineNo">079</span><a id="line.79"> *</a> |
| <span class="sourceLineNo">080</span><a id="line.80"> * @see #SoftHashMap(int)</a> |
| <span class="sourceLineNo">081</span><a id="line.81"> */</a> |
| <span class="sourceLineNo">082</span><a id="line.82"> public SoftHashMap() {</a> |
| <span class="sourceLineNo">083</span><a id="line.83"> this(DEFAULT_RETENTION_SIZE);</a> |
| <span class="sourceLineNo">084</span><a id="line.84"> }</a> |
| <span class="sourceLineNo">085</span><a id="line.85"></a> |
| <span class="sourceLineNo">086</span><a id="line.86"> /**</a> |
| <span class="sourceLineNo">087</span><a id="line.87"> * Creates a new SoftHashMap with the specified retention size.</a> |
| <span class="sourceLineNo">088</span><a id="line.88"> * <p/></a> |
| <span class="sourceLineNo">089</span><a id="line.89"> * The retention size (n) is the total number of most recent entries in the map that will be strongly referenced</a> |
| <span class="sourceLineNo">090</span><a id="line.90"> * (ie 'retained') to prevent them from being eagerly garbage collected. That is, the point of a SoftHashMap is to</a> |
| <span class="sourceLineNo">091</span><a id="line.91"> * allow the garbage collector to remove as many entries from this map as it desires, but there will always be (n)</a> |
| <span class="sourceLineNo">092</span><a id="line.92"> * elements retained after a GC due to the strong references.</a> |
| <span class="sourceLineNo">093</span><a id="line.93"> * <p/></a> |
| <span class="sourceLineNo">094</span><a id="line.94"> * Note that in a highly concurrent environments the exact total number of strong references may differ slightly</a> |
| <span class="sourceLineNo">095</span><a id="line.95"> * than the actual <code>retentionSize</code> value. This number is intended to be a best-effort retention low</a> |
| <span class="sourceLineNo">096</span><a id="line.96"> * water mark.</a> |
| <span class="sourceLineNo">097</span><a id="line.97"> *</a> |
| <span class="sourceLineNo">098</span><a id="line.98"> * @param retentionSize the total number of most recent entries in the map that will be strongly referenced</a> |
| <span class="sourceLineNo">099</span><a id="line.99"> * (retained), preventing them from being eagerly garbage collected by the JVM.</a> |
| <span class="sourceLineNo">100</span><a id="line.100"> */</a> |
| <span class="sourceLineNo">101</span><a id="line.101"> @SuppressWarnings({"unchecked"})</a> |
| <span class="sourceLineNo">102</span><a id="line.102"> public SoftHashMap(int retentionSize) {</a> |
| <span class="sourceLineNo">103</span><a id="line.103"> super();</a> |
| <span class="sourceLineNo">104</span><a id="line.104"> RETENTION_SIZE = Math.max(0, retentionSize);</a> |
| <span class="sourceLineNo">105</span><a id="line.105"> queue = new ReferenceQueue<V>();</a> |
| <span class="sourceLineNo">106</span><a id="line.106"> strongReferencesLock = new ReentrantLock();</a> |
| <span class="sourceLineNo">107</span><a id="line.107"> map = new ConcurrentHashMap<K, SoftValue<V, K>>();</a> |
| <span class="sourceLineNo">108</span><a id="line.108"> strongReferences = new ConcurrentLinkedQueue<V>();</a> |
| <span class="sourceLineNo">109</span><a id="line.109"> }</a> |
| <span class="sourceLineNo">110</span><a id="line.110"></a> |
| <span class="sourceLineNo">111</span><a id="line.111"> /**</a> |
| <span class="sourceLineNo">112</span><a id="line.112"> * Creates a {@code SoftHashMap} backed by the specified {@code source}, with a default retention</a> |
| <span class="sourceLineNo">113</span><a id="line.113"> * size of {@link #DEFAULT_RETENTION_SIZE DEFAULT_RETENTION_SIZE} (100 entries).</a> |
| <span class="sourceLineNo">114</span><a id="line.114"> *</a> |
| <span class="sourceLineNo">115</span><a id="line.115"> * @param source the backing map to populate this {@code SoftHashMap}</a> |
| <span class="sourceLineNo">116</span><a id="line.116"> * @see #SoftHashMap(Map,int)</a> |
| <span class="sourceLineNo">117</span><a id="line.117"> */</a> |
| <span class="sourceLineNo">118</span><a id="line.118"> public SoftHashMap(Map<K, V> source) {</a> |
| <span class="sourceLineNo">119</span><a id="line.119"> this(DEFAULT_RETENTION_SIZE);</a> |
| <span class="sourceLineNo">120</span><a id="line.120"> putAll(source);</a> |
| <span class="sourceLineNo">121</span><a id="line.121"> }</a> |
| <span class="sourceLineNo">122</span><a id="line.122"></a> |
| <span class="sourceLineNo">123</span><a id="line.123"> /**</a> |
| <span class="sourceLineNo">124</span><a id="line.124"> * Creates a {@code SoftHashMap} backed by the specified {@code source}, with the specified retention size.</a> |
| <span class="sourceLineNo">125</span><a id="line.125"> * <p/></a> |
| <span class="sourceLineNo">126</span><a id="line.126"> * The retention size (n) is the total number of most recent entries in the map that will be strongly referenced</a> |
| <span class="sourceLineNo">127</span><a id="line.127"> * (ie 'retained') to prevent them from being eagerly garbage collected. That is, the point of a SoftHashMap is to</a> |
| <span class="sourceLineNo">128</span><a id="line.128"> * allow the garbage collector to remove as many entries from this map as it desires, but there will always be (n)</a> |
| <span class="sourceLineNo">129</span><a id="line.129"> * elements retained after a GC due to the strong references.</a> |
| <span class="sourceLineNo">130</span><a id="line.130"> * <p/></a> |
| <span class="sourceLineNo">131</span><a id="line.131"> * Note that in a highly concurrent environments the exact total number of strong references may differ slightly</a> |
| <span class="sourceLineNo">132</span><a id="line.132"> * than the actual <code>retentionSize</code> value. This number is intended to be a best-effort retention low</a> |
| <span class="sourceLineNo">133</span><a id="line.133"> * water mark.</a> |
| <span class="sourceLineNo">134</span><a id="line.134"> *</a> |
| <span class="sourceLineNo">135</span><a id="line.135"> * @param source the backing map to populate this {@code SoftHashMap}</a> |
| <span class="sourceLineNo">136</span><a id="line.136"> * @param retentionSize the total number of most recent entries in the map that will be strongly referenced</a> |
| <span class="sourceLineNo">137</span><a id="line.137"> * (retained), preventing them from being eagerly garbage collected by the JVM.</a> |
| <span class="sourceLineNo">138</span><a id="line.138"> */</a> |
| <span class="sourceLineNo">139</span><a id="line.139"> public SoftHashMap(Map<K, V> source, int retentionSize) {</a> |
| <span class="sourceLineNo">140</span><a id="line.140"> this(retentionSize);</a> |
| <span class="sourceLineNo">141</span><a id="line.141"> putAll(source);</a> |
| <span class="sourceLineNo">142</span><a id="line.142"> }</a> |
| <span class="sourceLineNo">143</span><a id="line.143"></a> |
| <span class="sourceLineNo">144</span><a id="line.144"> public V get(Object key) {</a> |
| <span class="sourceLineNo">145</span><a id="line.145"> processQueue();</a> |
| <span class="sourceLineNo">146</span><a id="line.146"></a> |
| <span class="sourceLineNo">147</span><a id="line.147"> V result = null;</a> |
| <span class="sourceLineNo">148</span><a id="line.148"> SoftValue<V, K> value = map.get(key);</a> |
| <span class="sourceLineNo">149</span><a id="line.149"></a> |
| <span class="sourceLineNo">150</span><a id="line.150"> if (value != null) {</a> |
| <span class="sourceLineNo">151</span><a id="line.151"> //unwrap the 'real' value from the SoftReference</a> |
| <span class="sourceLineNo">152</span><a id="line.152"> result = value.get();</a> |
| <span class="sourceLineNo">153</span><a id="line.153"> if (result == null) {</a> |
| <span class="sourceLineNo">154</span><a id="line.154"> //The wrapped value was garbage collected, so remove this entry from the backing map:</a> |
| <span class="sourceLineNo">155</span><a id="line.155"> //noinspection SuspiciousMethodCalls</a> |
| <span class="sourceLineNo">156</span><a id="line.156"> map.remove(key);</a> |
| <span class="sourceLineNo">157</span><a id="line.157"> } else {</a> |
| <span class="sourceLineNo">158</span><a id="line.158"> //Add this value to the beginning of the strong reference queue (FIFO).</a> |
| <span class="sourceLineNo">159</span><a id="line.159"> addToStrongReferences(result);</a> |
| <span class="sourceLineNo">160</span><a id="line.160"> }</a> |
| <span class="sourceLineNo">161</span><a id="line.161"> }</a> |
| <span class="sourceLineNo">162</span><a id="line.162"> return result;</a> |
| <span class="sourceLineNo">163</span><a id="line.163"> }</a> |
| <span class="sourceLineNo">164</span><a id="line.164"></a> |
| <span class="sourceLineNo">165</span><a id="line.165"> private void addToStrongReferences(V result) {</a> |
| <span class="sourceLineNo">166</span><a id="line.166"> strongReferencesLock.lock();</a> |
| <span class="sourceLineNo">167</span><a id="line.167"> try {</a> |
| <span class="sourceLineNo">168</span><a id="line.168"> strongReferences.add(result);</a> |
| <span class="sourceLineNo">169</span><a id="line.169"> trimStrongReferencesIfNecessary();</a> |
| <span class="sourceLineNo">170</span><a id="line.170"> } finally {</a> |
| <span class="sourceLineNo">171</span><a id="line.171"> strongReferencesLock.unlock();</a> |
| <span class="sourceLineNo">172</span><a id="line.172"> }</a> |
| <span class="sourceLineNo">173</span><a id="line.173"></a> |
| <span class="sourceLineNo">174</span><a id="line.174"> }</a> |
| <span class="sourceLineNo">175</span><a id="line.175"></a> |
| <span class="sourceLineNo">176</span><a id="line.176"> //Guarded by the strongReferencesLock in the addToStrongReferences method</a> |
| <span class="sourceLineNo">177</span><a id="line.177"></a> |
| <span class="sourceLineNo">178</span><a id="line.178"> private void trimStrongReferencesIfNecessary() {</a> |
| <span class="sourceLineNo">179</span><a id="line.179"> //trim the strong ref queue if necessary:</a> |
| <span class="sourceLineNo">180</span><a id="line.180"> while (strongReferences.size() > RETENTION_SIZE) {</a> |
| <span class="sourceLineNo">181</span><a id="line.181"> strongReferences.poll();</a> |
| <span class="sourceLineNo">182</span><a id="line.182"> }</a> |
| <span class="sourceLineNo">183</span><a id="line.183"> }</a> |
| <span class="sourceLineNo">184</span><a id="line.184"></a> |
| <span class="sourceLineNo">185</span><a id="line.185"> /**</a> |
| <span class="sourceLineNo">186</span><a id="line.186"> * Traverses the ReferenceQueue and removes garbage-collected SoftValue objects from the backing map</a> |
| <span class="sourceLineNo">187</span><a id="line.187"> * by looking them up using the SoftValue.key data member.</a> |
| <span class="sourceLineNo">188</span><a id="line.188"> */</a> |
| <span class="sourceLineNo">189</span><a id="line.189"> private void processQueue() {</a> |
| <span class="sourceLineNo">190</span><a id="line.190"> SoftValue sv;</a> |
| <span class="sourceLineNo">191</span><a id="line.191"> while ((sv = (SoftValue) queue.poll()) != null) {</a> |
| <span class="sourceLineNo">192</span><a id="line.192"> //noinspection SuspiciousMethodCalls</a> |
| <span class="sourceLineNo">193</span><a id="line.193"> map.remove(sv.key); // we can access private data!</a> |
| <span class="sourceLineNo">194</span><a id="line.194"> }</a> |
| <span class="sourceLineNo">195</span><a id="line.195"> }</a> |
| <span class="sourceLineNo">196</span><a id="line.196"></a> |
| <span class="sourceLineNo">197</span><a id="line.197"> public boolean isEmpty() {</a> |
| <span class="sourceLineNo">198</span><a id="line.198"> processQueue();</a> |
| <span class="sourceLineNo">199</span><a id="line.199"> return map.isEmpty();</a> |
| <span class="sourceLineNo">200</span><a id="line.200"> }</a> |
| <span class="sourceLineNo">201</span><a id="line.201"></a> |
| <span class="sourceLineNo">202</span><a id="line.202"> public boolean containsKey(Object key) {</a> |
| <span class="sourceLineNo">203</span><a id="line.203"> processQueue();</a> |
| <span class="sourceLineNo">204</span><a id="line.204"> return map.containsKey(key);</a> |
| <span class="sourceLineNo">205</span><a id="line.205"> }</a> |
| <span class="sourceLineNo">206</span><a id="line.206"></a> |
| <span class="sourceLineNo">207</span><a id="line.207"> public boolean containsValue(Object value) {</a> |
| <span class="sourceLineNo">208</span><a id="line.208"> processQueue();</a> |
| <span class="sourceLineNo">209</span><a id="line.209"> Collection values = values();</a> |
| <span class="sourceLineNo">210</span><a id="line.210"> return values != null && values.contains(value);</a> |
| <span class="sourceLineNo">211</span><a id="line.211"> }</a> |
| <span class="sourceLineNo">212</span><a id="line.212"></a> |
| <span class="sourceLineNo">213</span><a id="line.213"> public void putAll(Map<? extends K, ? extends V> m) {</a> |
| <span class="sourceLineNo">214</span><a id="line.214"> if (m == null || m.isEmpty()) {</a> |
| <span class="sourceLineNo">215</span><a id="line.215"> processQueue();</a> |
| <span class="sourceLineNo">216</span><a id="line.216"> return;</a> |
| <span class="sourceLineNo">217</span><a id="line.217"> }</a> |
| <span class="sourceLineNo">218</span><a id="line.218"> for (Map.Entry<? extends K, ? extends V> entry : m.entrySet()) {</a> |
| <span class="sourceLineNo">219</span><a id="line.219"> put(entry.getKey(), entry.getValue());</a> |
| <span class="sourceLineNo">220</span><a id="line.220"> }</a> |
| <span class="sourceLineNo">221</span><a id="line.221"> }</a> |
| <span class="sourceLineNo">222</span><a id="line.222"></a> |
| <span class="sourceLineNo">223</span><a id="line.223"> public Set<K> keySet() {</a> |
| <span class="sourceLineNo">224</span><a id="line.224"> processQueue();</a> |
| <span class="sourceLineNo">225</span><a id="line.225"> return map.keySet();</a> |
| <span class="sourceLineNo">226</span><a id="line.226"> }</a> |
| <span class="sourceLineNo">227</span><a id="line.227"></a> |
| <span class="sourceLineNo">228</span><a id="line.228"> public Collection<V> values() {</a> |
| <span class="sourceLineNo">229</span><a id="line.229"> processQueue();</a> |
| <span class="sourceLineNo">230</span><a id="line.230"> Collection<K> keys = map.keySet();</a> |
| <span class="sourceLineNo">231</span><a id="line.231"> if (keys.isEmpty()) {</a> |
| <span class="sourceLineNo">232</span><a id="line.232"> //noinspection unchecked</a> |
| <span class="sourceLineNo">233</span><a id="line.233"> return Collections.EMPTY_SET;</a> |
| <span class="sourceLineNo">234</span><a id="line.234"> }</a> |
| <span class="sourceLineNo">235</span><a id="line.235"> Collection<V> values = new ArrayList<V>(keys.size());</a> |
| <span class="sourceLineNo">236</span><a id="line.236"> for (K key : keys) {</a> |
| <span class="sourceLineNo">237</span><a id="line.237"> V v = get(key);</a> |
| <span class="sourceLineNo">238</span><a id="line.238"> if (v != null) {</a> |
| <span class="sourceLineNo">239</span><a id="line.239"> values.add(v);</a> |
| <span class="sourceLineNo">240</span><a id="line.240"> }</a> |
| <span class="sourceLineNo">241</span><a id="line.241"> }</a> |
| <span class="sourceLineNo">242</span><a id="line.242"> return values;</a> |
| <span class="sourceLineNo">243</span><a id="line.243"> }</a> |
| <span class="sourceLineNo">244</span><a id="line.244"></a> |
| <span class="sourceLineNo">245</span><a id="line.245"> /**</a> |
| <span class="sourceLineNo">246</span><a id="line.246"> * Creates a new entry, but wraps the value in a SoftValue instance to enable auto garbage collection.</a> |
| <span class="sourceLineNo">247</span><a id="line.247"> */</a> |
| <span class="sourceLineNo">248</span><a id="line.248"> public V put(K key, V value) {</a> |
| <span class="sourceLineNo">249</span><a id="line.249"> processQueue(); // throw out garbage collected values first</a> |
| <span class="sourceLineNo">250</span><a id="line.250"> SoftValue<V, K> sv = new SoftValue<V, K>(value, key, queue);</a> |
| <span class="sourceLineNo">251</span><a id="line.251"> SoftValue<V, K> previous = map.put(key, sv);</a> |
| <span class="sourceLineNo">252</span><a id="line.252"> addToStrongReferences(value);</a> |
| <span class="sourceLineNo">253</span><a id="line.253"> return previous != null ? previous.get() : null;</a> |
| <span class="sourceLineNo">254</span><a id="line.254"> }</a> |
| <span class="sourceLineNo">255</span><a id="line.255"></a> |
| <span class="sourceLineNo">256</span><a id="line.256"> public V remove(Object key) {</a> |
| <span class="sourceLineNo">257</span><a id="line.257"> processQueue(); // throw out garbage collected values first</a> |
| <span class="sourceLineNo">258</span><a id="line.258"> SoftValue<V, K> raw = map.remove(key);</a> |
| <span class="sourceLineNo">259</span><a id="line.259"> return raw != null ? raw.get() : null;</a> |
| <span class="sourceLineNo">260</span><a id="line.260"> }</a> |
| <span class="sourceLineNo">261</span><a id="line.261"></a> |
| <span class="sourceLineNo">262</span><a id="line.262"> public void clear() {</a> |
| <span class="sourceLineNo">263</span><a id="line.263"> strongReferencesLock.lock();</a> |
| <span class="sourceLineNo">264</span><a id="line.264"> try {</a> |
| <span class="sourceLineNo">265</span><a id="line.265"> strongReferences.clear();</a> |
| <span class="sourceLineNo">266</span><a id="line.266"> } finally {</a> |
| <span class="sourceLineNo">267</span><a id="line.267"> strongReferencesLock.unlock();</a> |
| <span class="sourceLineNo">268</span><a id="line.268"> }</a> |
| <span class="sourceLineNo">269</span><a id="line.269"> processQueue(); // throw out garbage collected values</a> |
| <span class="sourceLineNo">270</span><a id="line.270"> map.clear();</a> |
| <span class="sourceLineNo">271</span><a id="line.271"> }</a> |
| <span class="sourceLineNo">272</span><a id="line.272"></a> |
| <span class="sourceLineNo">273</span><a id="line.273"> public int size() {</a> |
| <span class="sourceLineNo">274</span><a id="line.274"> processQueue(); // throw out garbage collected values first</a> |
| <span class="sourceLineNo">275</span><a id="line.275"> return map.size();</a> |
| <span class="sourceLineNo">276</span><a id="line.276"> }</a> |
| <span class="sourceLineNo">277</span><a id="line.277"></a> |
| <span class="sourceLineNo">278</span><a id="line.278"> public Set<Map.Entry<K, V>> entrySet() {</a> |
| <span class="sourceLineNo">279</span><a id="line.279"> processQueue(); // throw out garbage collected values first</a> |
| <span class="sourceLineNo">280</span><a id="line.280"> Collection<K> keys = map.keySet();</a> |
| <span class="sourceLineNo">281</span><a id="line.281"> if (keys.isEmpty()) {</a> |
| <span class="sourceLineNo">282</span><a id="line.282"> //noinspection unchecked</a> |
| <span class="sourceLineNo">283</span><a id="line.283"> return Collections.EMPTY_SET;</a> |
| <span class="sourceLineNo">284</span><a id="line.284"> }</a> |
| <span class="sourceLineNo">285</span><a id="line.285"></a> |
| <span class="sourceLineNo">286</span><a id="line.286"> Map<K, V> kvPairs = new HashMap<K, V>(keys.size());</a> |
| <span class="sourceLineNo">287</span><a id="line.287"> for (K key : keys) {</a> |
| <span class="sourceLineNo">288</span><a id="line.288"> V v = get(key);</a> |
| <span class="sourceLineNo">289</span><a id="line.289"> if (v != null) {</a> |
| <span class="sourceLineNo">290</span><a id="line.290"> kvPairs.put(key, v);</a> |
| <span class="sourceLineNo">291</span><a id="line.291"> }</a> |
| <span class="sourceLineNo">292</span><a id="line.292"> }</a> |
| <span class="sourceLineNo">293</span><a id="line.293"> return kvPairs.entrySet();</a> |
| <span class="sourceLineNo">294</span><a id="line.294"> }</a> |
| <span class="sourceLineNo">295</span><a id="line.295"></a> |
| <span class="sourceLineNo">296</span><a id="line.296"> /**</a> |
| <span class="sourceLineNo">297</span><a id="line.297"> * We define our own subclass of SoftReference which contains</a> |
| <span class="sourceLineNo">298</span><a id="line.298"> * not only the value but also the key to make it easier to find</a> |
| <span class="sourceLineNo">299</span><a id="line.299"> * the entry in the HashMap after it's been garbage collected.</a> |
| <span class="sourceLineNo">300</span><a id="line.300"> */</a> |
| <span class="sourceLineNo">301</span><a id="line.301"> private static class SoftValue<V, K> extends SoftReference<V> {</a> |
| <span class="sourceLineNo">302</span><a id="line.302"></a> |
| <span class="sourceLineNo">303</span><a id="line.303"> private final K key;</a> |
| <span class="sourceLineNo">304</span><a id="line.304"></a> |
| <span class="sourceLineNo">305</span><a id="line.305"> /**</a> |
| <span class="sourceLineNo">306</span><a id="line.306"> * Constructs a new instance, wrapping the value, key, and queue, as</a> |
| <span class="sourceLineNo">307</span><a id="line.307"> * required by the superclass.</a> |
| <span class="sourceLineNo">308</span><a id="line.308"> *</a> |
| <span class="sourceLineNo">309</span><a id="line.309"> * @param value the map value</a> |
| <span class="sourceLineNo">310</span><a id="line.310"> * @param key the map key</a> |
| <span class="sourceLineNo">311</span><a id="line.311"> * @param queue the soft reference queue to poll to determine if the entry had been reaped by the GC.</a> |
| <span class="sourceLineNo">312</span><a id="line.312"> */</a> |
| <span class="sourceLineNo">313</span><a id="line.313"> private SoftValue(V value, K key, ReferenceQueue<? super V> queue) {</a> |
| <span class="sourceLineNo">314</span><a id="line.314"> super(value, queue);</a> |
| <span class="sourceLineNo">315</span><a id="line.315"> this.key = key;</a> |
| <span class="sourceLineNo">316</span><a id="line.316"> }</a> |
| <span class="sourceLineNo">317</span><a id="line.317"></a> |
| <span class="sourceLineNo">318</span><a id="line.318"> }</a> |
| <span class="sourceLineNo">319</span><a id="line.319">}</a> |
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| </pre> |
| </div> |
| </main> |
| </body> |
| </html> |
