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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.event.support;</a> |
| <span class="sourceLineNo">020</span><a id="line.20"></a> |
| <span class="sourceLineNo">021</span><a id="line.21">import org.apache.shiro.event.EventBus;</a> |
| <span class="sourceLineNo">022</span><a id="line.22">import org.slf4j.Logger;</a> |
| <span class="sourceLineNo">023</span><a id="line.23">import org.slf4j.LoggerFactory;</a> |
| <span class="sourceLineNo">024</span><a id="line.24"></a> |
| <span class="sourceLineNo">025</span><a id="line.25">import java.util.ArrayList;</a> |
| <span class="sourceLineNo">026</span><a id="line.26">import java.util.Collections;</a> |
| <span class="sourceLineNo">027</span><a id="line.27">import java.util.HashSet;</a> |
| <span class="sourceLineNo">028</span><a id="line.28">import java.util.LinkedHashMap;</a> |
| <span class="sourceLineNo">029</span><a id="line.29">import java.util.List;</a> |
| <span class="sourceLineNo">030</span><a id="line.30">import java.util.Map;</a> |
| <span class="sourceLineNo">031</span><a id="line.31">import java.util.Set;</a> |
| <span class="sourceLineNo">032</span><a id="line.32">import java.util.concurrent.locks.Lock;</a> |
| <span class="sourceLineNo">033</span><a id="line.33">import java.util.concurrent.locks.ReentrantReadWriteLock;</a> |
| <span class="sourceLineNo">034</span><a id="line.34"></a> |
| <span class="sourceLineNo">035</span><a id="line.35">/**</a> |
| <span class="sourceLineNo">036</span><a id="line.36"> * A default event bus implementation that synchronously publishes events to registered listeners. Listeners can be</a> |
| <span class="sourceLineNo">037</span><a id="line.37"> * registered or unregistered for events as necessary.</a> |
| <span class="sourceLineNo">038</span><a id="line.38"> * <p/></a> |
| <span class="sourceLineNo">039</span><a id="line.39"> * An event bus enables a publish/subscribe paradigm within Shiro - components can publish or consume events they</a> |
| <span class="sourceLineNo">040</span><a id="line.40"> * find relevant without needing to be tightly coupled to other components. This affords great</a> |
| <span class="sourceLineNo">041</span><a id="line.41"> * flexibility within Shiro by promoting loose coupling and high cohesion between components and a much safer</a> |
| <span class="sourceLineNo">042</span><a id="line.42"> * pluggable architecture that is more resilient to change over time.</a> |
| <span class="sourceLineNo">043</span><a id="line.43"> * <h2>Sending Events</h2></a> |
| <span class="sourceLineNo">044</span><a id="line.44"> * If a component wishes to publish events to other components:</a> |
| <span class="sourceLineNo">045</span><a id="line.45"> * <pre></a> |
| <span class="sourceLineNo">046</span><a id="line.46"> * MyEvent myEvent = createMyEvent();</a> |
| <span class="sourceLineNo">047</span><a id="line.47"> * eventBus.publish(myEvent);</a> |
| <span class="sourceLineNo">048</span><a id="line.48"> * </pre></a> |
| <span class="sourceLineNo">049</span><a id="line.49"> * The event bus will determine the type of event and then dispatch the event to components that wish to receive</a> |
| <span class="sourceLineNo">050</span><a id="line.50"> * events of that type.</a> |
| <span class="sourceLineNo">051</span><a id="line.51"> * <h2>Receiving Events</h2></a> |
| <span class="sourceLineNo">052</span><a id="line.52"> * A component can receive events of interest by doing the following.</a> |
| <span class="sourceLineNo">053</span><a id="line.53"> * <ol></a> |
| <span class="sourceLineNo">054</span><a id="line.54"> * <li>For each type of event you wish to consume, create a public method that accepts a single event argument.</a> |
| <span class="sourceLineNo">055</span><a id="line.55"> * The method argument type indicates the type of event to receive.</li></a> |
| <span class="sourceLineNo">056</span><a id="line.56"> * <li>Annotate each of these public methods with the {@link org.apache.shiro.event.Subscribe Subscribe} annotation.</li></a> |
| <span class="sourceLineNo">057</span><a id="line.57"> * <li>Register the component with the event bus:</a> |
| <span class="sourceLineNo">058</span><a id="line.58"> * <pre></a> |
| <span class="sourceLineNo">059</span><a id="line.59"> * eventBus.register(myComponent);</a> |
| <span class="sourceLineNo">060</span><a id="line.60"> * </pre></a> |
| <span class="sourceLineNo">061</span><a id="line.61"> * </li></a> |
| <span class="sourceLineNo">062</span><a id="line.62"> * </ol></a> |
| <span class="sourceLineNo">063</span><a id="line.63"> * After registering the component, when when an event of a respective type is published, the component's</a> |
| <span class="sourceLineNo">064</span><a id="line.64"> * {@code Subscribe}-annotated method(s) will be invoked as expected.</a> |
| <span class="sourceLineNo">065</span><a id="line.65"> *</a> |
| <span class="sourceLineNo">066</span><a id="line.66"> * This design (and its constituent helper components) was largely influenced by</a> |
| <span class="sourceLineNo">067</span><a id="line.67"> * Guava's <a href="http://docs.guava-libraries.googlecode.com/git/javadoc/com/google/common/eventbus/EventBus.html">EventBus</a></a> |
| <span class="sourceLineNo">068</span><a id="line.68"> * concept, although no code was shared/imported (even though Guava is Apache 2.0 licensed and could have</a> |
| <span class="sourceLineNo">069</span><a id="line.69"> * been used).</a> |
| <span class="sourceLineNo">070</span><a id="line.70"> *</a> |
| <span class="sourceLineNo">071</span><a id="line.71"> * This implementation is thread-safe and may be used concurrently.</a> |
| <span class="sourceLineNo">072</span><a id="line.72"> *</a> |
| <span class="sourceLineNo">073</span><a id="line.73"> * @since 1.3</a> |
| <span class="sourceLineNo">074</span><a id="line.74"> */</a> |
| <span class="sourceLineNo">075</span><a id="line.75">public class DefaultEventBus implements EventBus {</a> |
| <span class="sourceLineNo">076</span><a id="line.76"></a> |
| <span class="sourceLineNo">077</span><a id="line.77"> private static final Logger log = LoggerFactory.getLogger(DefaultEventBus.class);</a> |
| <span class="sourceLineNo">078</span><a id="line.78"></a> |
| <span class="sourceLineNo">079</span><a id="line.79"> private static final String EVENT_LISTENER_ERROR_MSG = "Event listener processing failed. Listeners should " +</a> |
| <span class="sourceLineNo">080</span><a id="line.80"> "generally handle exceptions directly and not propagate to the event bus.";</a> |
| <span class="sourceLineNo">081</span><a id="line.81"></a> |
| <span class="sourceLineNo">082</span><a id="line.82"> //this is stateless, we can retain a static final reference:</a> |
| <span class="sourceLineNo">083</span><a id="line.83"> private static final EventListenerComparator EVENT_LISTENER_COMPARATOR = new EventListenerComparator();</a> |
| <span class="sourceLineNo">084</span><a id="line.84"></a> |
| <span class="sourceLineNo">085</span><a id="line.85"> private EventListenerResolver eventListenerResolver;</a> |
| <span class="sourceLineNo">086</span><a id="line.86"></a> |
| <span class="sourceLineNo">087</span><a id="line.87"> //We want to preserve registration order to deliver events to objects in the order that they are registered</a> |
| <span class="sourceLineNo">088</span><a id="line.88"> //with the event bus. This has the nice effect that any Shiro system-level components that are registered first</a> |
| <span class="sourceLineNo">089</span><a id="line.89"> //(likely to happen upon startup) have precedence over those registered by end-user components later.</a> |
| <span class="sourceLineNo">090</span><a id="line.90"> //</a> |
| <span class="sourceLineNo">091</span><a id="line.91"> //One might think that this could have been done by just using a ConcurrentSkipListMap (which is available only on</a> |
| <span class="sourceLineNo">092</span><a id="line.92"> //JDK 6 or later). However, this approach requires the implementation of a Comparator to sort elements, and this</a> |
| <span class="sourceLineNo">093</span><a id="line.93"> //surfaces a problem: for any given random event listener, there isn't any guaranteed property to exist that can be</a> |
| <span class="sourceLineNo">094</span><a id="line.94"> //inspected to determine order of registration, since registration order is an artifact of this EventBus</a> |
| <span class="sourceLineNo">095</span><a id="line.95"> //implementation, not the listeners themselves.</a> |
| <span class="sourceLineNo">096</span><a id="line.96"> //</a> |
| <span class="sourceLineNo">097</span><a id="line.97"> //Therefore, we use a simple concurrent lock to wrap a LinkedHashMap - the LinkedHashMap retains insertion order</a> |
| <span class="sourceLineNo">098</span><a id="line.98"> //and the lock provides thread-safety in probably a much simpler mechanism than attempting to write a</a> |
| <span class="sourceLineNo">099</span><a id="line.99"> //EventBus-specific Comparator. This technique is also likely to be faster than a ConcurrentSkipListMap, which</a> |
| <span class="sourceLineNo">100</span><a id="line.100"> //is about 3-5 times slower than a standard ConcurrentMap.</a> |
| <span class="sourceLineNo">101</span><a id="line.101"> private final Map<Object, Subscription> registry;</a> |
| <span class="sourceLineNo">102</span><a id="line.102"> private final Lock registryReadLock;</a> |
| <span class="sourceLineNo">103</span><a id="line.103"> private final Lock registryWriteLock;</a> |
| <span class="sourceLineNo">104</span><a id="line.104"></a> |
| <span class="sourceLineNo">105</span><a id="line.105"> public DefaultEventBus() {</a> |
| <span class="sourceLineNo">106</span><a id="line.106"> this.registry = new LinkedHashMap<Object, Subscription>(); //not thread safe, so we need locks:</a> |
| <span class="sourceLineNo">107</span><a id="line.107"> ReentrantReadWriteLock rwl = new ReentrantReadWriteLock();</a> |
| <span class="sourceLineNo">108</span><a id="line.108"> this.registryReadLock = rwl.readLock();</a> |
| <span class="sourceLineNo">109</span><a id="line.109"> this.registryWriteLock = rwl.writeLock();</a> |
| <span class="sourceLineNo">110</span><a id="line.110"> this.eventListenerResolver = new AnnotationEventListenerResolver();</a> |
| <span class="sourceLineNo">111</span><a id="line.111"> }</a> |
| <span class="sourceLineNo">112</span><a id="line.112"></a> |
| <span class="sourceLineNo">113</span><a id="line.113"> public EventListenerResolver getEventListenerResolver() {</a> |
| <span class="sourceLineNo">114</span><a id="line.114"> return eventListenerResolver;</a> |
| <span class="sourceLineNo">115</span><a id="line.115"> }</a> |
| <span class="sourceLineNo">116</span><a id="line.116"></a> |
| <span class="sourceLineNo">117</span><a id="line.117"> public void setEventListenerResolver(EventListenerResolver eventListenerResolver) {</a> |
| <span class="sourceLineNo">118</span><a id="line.118"> this.eventListenerResolver = eventListenerResolver;</a> |
| <span class="sourceLineNo">119</span><a id="line.119"> }</a> |
| <span class="sourceLineNo">120</span><a id="line.120"></a> |
| <span class="sourceLineNo">121</span><a id="line.121"> public void publish(Object event) {</a> |
| <span class="sourceLineNo">122</span><a id="line.122"> if (event == null) {</a> |
| <span class="sourceLineNo">123</span><a id="line.123"> log.info("Received null event for publishing. Ignoring and returning.");</a> |
| <span class="sourceLineNo">124</span><a id="line.124"> return;</a> |
| <span class="sourceLineNo">125</span><a id="line.125"> }</a> |
| <span class="sourceLineNo">126</span><a id="line.126"></a> |
| <span class="sourceLineNo">127</span><a id="line.127"> registryReadLock.lock();</a> |
| <span class="sourceLineNo">128</span><a id="line.128"> try {</a> |
| <span class="sourceLineNo">129</span><a id="line.129"> //performing the entire iteration within the lock will be a slow operation if the registry has a lot of</a> |
| <span class="sourceLineNo">130</span><a id="line.130"> //contention. However, it is expected that the very large majority of cases the registry will be</a> |
| <span class="sourceLineNo">131</span><a id="line.131"> //read-mostly with very little writes (registrations or removals) occurring during a typical application</a> |
| <span class="sourceLineNo">132</span><a id="line.132"> //lifetime.</a> |
| <span class="sourceLineNo">133</span><a id="line.133"> //</a> |
| <span class="sourceLineNo">134</span><a id="line.134"> //The alternative would be to copy the registry.values() collection to a new LinkedHashSet within the lock</a> |
| <span class="sourceLineNo">135</span><a id="line.135"> //only and the iteration on this new collection could be outside the lock. This has the performance penalty</a> |
| <span class="sourceLineNo">136</span><a id="line.136"> //however of always creating a new collection every time an event is published, which could be more</a> |
| <span class="sourceLineNo">137</span><a id="line.137"> //costly for the majority of applications, especially if the number of listeners is large.</a> |
| <span class="sourceLineNo">138</span><a id="line.138"> //</a> |
| <span class="sourceLineNo">139</span><a id="line.139"> //Finally, the read lock is re-entrant, so multiple publish calls will be</a> |
| <span class="sourceLineNo">140</span><a id="line.140"> //concurrent without penalty since publishing is a read-only operation on the registry.</a> |
| <span class="sourceLineNo">141</span><a id="line.141"></a> |
| <span class="sourceLineNo">142</span><a id="line.142"> for (Subscription subscription : this.registry.values()) {</a> |
| <span class="sourceLineNo">143</span><a id="line.143"> subscription.onEvent(event);</a> |
| <span class="sourceLineNo">144</span><a id="line.144"> }</a> |
| <span class="sourceLineNo">145</span><a id="line.145"> } finally {</a> |
| <span class="sourceLineNo">146</span><a id="line.146"> registryReadLock.unlock();</a> |
| <span class="sourceLineNo">147</span><a id="line.147"> }</a> |
| <span class="sourceLineNo">148</span><a id="line.148"> }</a> |
| <span class="sourceLineNo">149</span><a id="line.149"></a> |
| <span class="sourceLineNo">150</span><a id="line.150"> public void register(Object instance) {</a> |
| <span class="sourceLineNo">151</span><a id="line.151"> if (instance == null) {</a> |
| <span class="sourceLineNo">152</span><a id="line.152"> log.info("Received null instance for event listener registration. Ignoring registration request.");</a> |
| <span class="sourceLineNo">153</span><a id="line.153"> return;</a> |
| <span class="sourceLineNo">154</span><a id="line.154"> }</a> |
| <span class="sourceLineNo">155</span><a id="line.155"></a> |
| <span class="sourceLineNo">156</span><a id="line.156"> unregister(instance);</a> |
| <span class="sourceLineNo">157</span><a id="line.157"></a> |
| <span class="sourceLineNo">158</span><a id="line.158"> List<EventListener> listeners = getEventListenerResolver().getEventListeners(instance);</a> |
| <span class="sourceLineNo">159</span><a id="line.159"></a> |
| <span class="sourceLineNo">160</span><a id="line.160"> if (listeners == null || listeners.isEmpty()) {</a> |
| <span class="sourceLineNo">161</span><a id="line.161"> log.warn("Unable to resolve event listeners for subscriber instance [{}]. Ignoring registration request.",</a> |
| <span class="sourceLineNo">162</span><a id="line.162"> instance);</a> |
| <span class="sourceLineNo">163</span><a id="line.163"> return;</a> |
| <span class="sourceLineNo">164</span><a id="line.164"> }</a> |
| <span class="sourceLineNo">165</span><a id="line.165"></a> |
| <span class="sourceLineNo">166</span><a id="line.166"> Subscription subscription = new Subscription(listeners);</a> |
| <span class="sourceLineNo">167</span><a id="line.167"></a> |
| <span class="sourceLineNo">168</span><a id="line.168"> this.registryWriteLock.lock();</a> |
| <span class="sourceLineNo">169</span><a id="line.169"> try {</a> |
| <span class="sourceLineNo">170</span><a id="line.170"> this.registry.put(instance, subscription);</a> |
| <span class="sourceLineNo">171</span><a id="line.171"> } finally {</a> |
| <span class="sourceLineNo">172</span><a id="line.172"> this.registryWriteLock.unlock();</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"> public void unregister(Object instance) {</a> |
| <span class="sourceLineNo">177</span><a id="line.177"> if (instance == null) {</a> |
| <span class="sourceLineNo">178</span><a id="line.178"> return;</a> |
| <span class="sourceLineNo">179</span><a id="line.179"> }</a> |
| <span class="sourceLineNo">180</span><a id="line.180"> this.registryWriteLock.lock();</a> |
| <span class="sourceLineNo">181</span><a id="line.181"> try {</a> |
| <span class="sourceLineNo">182</span><a id="line.182"> this.registry.remove(instance);</a> |
| <span class="sourceLineNo">183</span><a id="line.183"> } finally {</a> |
| <span class="sourceLineNo">184</span><a id="line.184"> this.registryWriteLock.unlock();</a> |
| <span class="sourceLineNo">185</span><a id="line.185"> }</a> |
| <span class="sourceLineNo">186</span><a id="line.186"> }</a> |
| <span class="sourceLineNo">187</span><a id="line.187"></a> |
| <span class="sourceLineNo">188</span><a id="line.188"> private class Subscription {</a> |
| <span class="sourceLineNo">189</span><a id="line.189"></a> |
| <span class="sourceLineNo">190</span><a id="line.190"> private final List<EventListener> listeners;</a> |
| <span class="sourceLineNo">191</span><a id="line.191"></a> |
| <span class="sourceLineNo">192</span><a id="line.192"> public Subscription(List<EventListener> listeners) {</a> |
| <span class="sourceLineNo">193</span><a id="line.193"> List<EventListener> toSort = new ArrayList<EventListener>(listeners);</a> |
| <span class="sourceLineNo">194</span><a id="line.194"> Collections.sort(toSort, EVENT_LISTENER_COMPARATOR);</a> |
| <span class="sourceLineNo">195</span><a id="line.195"> this.listeners = toSort;</a> |
| <span class="sourceLineNo">196</span><a id="line.196"> }</a> |
| <span class="sourceLineNo">197</span><a id="line.197"></a> |
| <span class="sourceLineNo">198</span><a id="line.198"> public void onEvent(Object event) {</a> |
| <span class="sourceLineNo">199</span><a id="line.199"></a> |
| <span class="sourceLineNo">200</span><a id="line.200"> Set<Object> delivered = new HashSet<Object>();</a> |
| <span class="sourceLineNo">201</span><a id="line.201"></a> |
| <span class="sourceLineNo">202</span><a id="line.202"> for (EventListener listener : this.listeners) {</a> |
| <span class="sourceLineNo">203</span><a id="line.203"> Object target = listener;</a> |
| <span class="sourceLineNo">204</span><a id="line.204"> if (listener instanceof SingleArgumentMethodEventListener) {</a> |
| <span class="sourceLineNo">205</span><a id="line.205"> SingleArgumentMethodEventListener singleArgListener = (SingleArgumentMethodEventListener) listener;</a> |
| <span class="sourceLineNo">206</span><a id="line.206"> target = singleArgListener.getTarget();</a> |
| <span class="sourceLineNo">207</span><a id="line.207"> }</a> |
| <span class="sourceLineNo">208</span><a id="line.208"> if (listener.accepts(event) && !delivered.contains(target)) {</a> |
| <span class="sourceLineNo">209</span><a id="line.209"> try {</a> |
| <span class="sourceLineNo">210</span><a id="line.210"> listener.onEvent(event);</a> |
| <span class="sourceLineNo">211</span><a id="line.211"> } catch (Throwable t) {</a> |
| <span class="sourceLineNo">212</span><a id="line.212"> log.warn(EVENT_LISTENER_ERROR_MSG, t);</a> |
| <span class="sourceLineNo">213</span><a id="line.213"> }</a> |
| <span class="sourceLineNo">214</span><a id="line.214"> delivered.add(target);</a> |
| <span class="sourceLineNo">215</span><a id="line.215"> }</a> |
| <span class="sourceLineNo">216</span><a id="line.216"> }</a> |
| <span class="sourceLineNo">217</span><a id="line.217"> }</a> |
| <span class="sourceLineNo">218</span><a id="line.218"> }</a> |
| <span class="sourceLineNo">219</span><a id="line.219">}</a> |
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