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| <pre><span class="sourceLineNo">001</span>/*<a name="line.1"></a> |
| <span class="sourceLineNo">002</span> * Licensed to the Apache Software Foundation (ASF) under one<a name="line.2"></a> |
| <span class="sourceLineNo">003</span> * or more contributor license agreements. See the NOTICE file<a name="line.3"></a> |
| <span class="sourceLineNo">004</span> * distributed with this work for additional information<a name="line.4"></a> |
| <span class="sourceLineNo">005</span> * regarding copyright ownership. The ASF licenses this file<a name="line.5"></a> |
| <span class="sourceLineNo">006</span> * to you under the Apache License, Version 2.0 (the<a name="line.6"></a> |
| <span class="sourceLineNo">007</span> * "License"); you may not use this file except in compliance<a name="line.7"></a> |
| <span class="sourceLineNo">008</span> * with the License. You may obtain a copy of the License at<a name="line.8"></a> |
| <span class="sourceLineNo">009</span> *<a name="line.9"></a> |
| <span class="sourceLineNo">010</span> * http://www.apache.org/licenses/LICENSE-2.0<a name="line.10"></a> |
| <span class="sourceLineNo">011</span> *<a name="line.11"></a> |
| <span class="sourceLineNo">012</span> * Unless required by applicable law or agreed to in writing,<a name="line.12"></a> |
| <span class="sourceLineNo">013</span> * software distributed under the License is distributed on an<a name="line.13"></a> |
| <span class="sourceLineNo">014</span> * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY<a name="line.14"></a> |
| <span class="sourceLineNo">015</span> * KIND, either express or implied. See the License for the<a name="line.15"></a> |
| <span class="sourceLineNo">016</span> * specific language governing permissions and limitations<a name="line.16"></a> |
| <span class="sourceLineNo">017</span> * under the License.<a name="line.17"></a> |
| <span class="sourceLineNo">018</span> */<a name="line.18"></a> |
| <span class="sourceLineNo">019</span>package org.apache.shiro.event.support;<a name="line.19"></a> |
| <span class="sourceLineNo">020</span><a name="line.20"></a> |
| <span class="sourceLineNo">021</span>import org.apache.shiro.event.EventBus;<a name="line.21"></a> |
| <span class="sourceLineNo">022</span>import org.slf4j.Logger;<a name="line.22"></a> |
| <span class="sourceLineNo">023</span>import org.slf4j.LoggerFactory;<a name="line.23"></a> |
| <span class="sourceLineNo">024</span><a name="line.24"></a> |
| <span class="sourceLineNo">025</span>import java.util.ArrayList;<a name="line.25"></a> |
| <span class="sourceLineNo">026</span>import java.util.Collections;<a name="line.26"></a> |
| <span class="sourceLineNo">027</span>import java.util.HashSet;<a name="line.27"></a> |
| <span class="sourceLineNo">028</span>import java.util.LinkedHashMap;<a name="line.28"></a> |
| <span class="sourceLineNo">029</span>import java.util.List;<a name="line.29"></a> |
| <span class="sourceLineNo">030</span>import java.util.Map;<a name="line.30"></a> |
| <span class="sourceLineNo">031</span>import java.util.Set;<a name="line.31"></a> |
| <span class="sourceLineNo">032</span>import java.util.concurrent.locks.Lock;<a name="line.32"></a> |
| <span class="sourceLineNo">033</span>import java.util.concurrent.locks.ReentrantReadWriteLock;<a name="line.33"></a> |
| <span class="sourceLineNo">034</span><a name="line.34"></a> |
| <span class="sourceLineNo">035</span>/**<a name="line.35"></a> |
| <span class="sourceLineNo">036</span> * A default event bus implementation that synchronously publishes events to registered listeners. Listeners can be<a name="line.36"></a> |
| <span class="sourceLineNo">037</span> * registered or unregistered for events as necessary.<a name="line.37"></a> |
| <span class="sourceLineNo">038</span> * <p/><a name="line.38"></a> |
| <span class="sourceLineNo">039</span> * An event bus enables a publish/subscribe paradigm within Shiro - components can publish or consume events they<a name="line.39"></a> |
| <span class="sourceLineNo">040</span> * find relevant without needing to be tightly coupled to other components. This affords great<a name="line.40"></a> |
| <span class="sourceLineNo">041</span> * flexibility within Shiro by promoting loose coupling and high cohesion between components and a much safer<a name="line.41"></a> |
| <span class="sourceLineNo">042</span> * pluggable architecture that is more resilient to change over time.<a name="line.42"></a> |
| <span class="sourceLineNo">043</span> * <h2>Sending Events</h2><a name="line.43"></a> |
| <span class="sourceLineNo">044</span> * If a component wishes to publish events to other components:<a name="line.44"></a> |
| <span class="sourceLineNo">045</span> * <pre><a name="line.45"></a> |
| <span class="sourceLineNo">046</span> * MyEvent myEvent = createMyEvent();<a name="line.46"></a> |
| <span class="sourceLineNo">047</span> * eventBus.publish(myEvent);<a name="line.47"></a> |
| <span class="sourceLineNo">048</span> * </pre><a name="line.48"></a> |
| <span class="sourceLineNo">049</span> * The event bus will determine the type of event and then dispatch the event to components that wish to receive<a name="line.49"></a> |
| <span class="sourceLineNo">050</span> * events of that type.<a name="line.50"></a> |
| <span class="sourceLineNo">051</span> * <h2>Receiving Events</h2><a name="line.51"></a> |
| <span class="sourceLineNo">052</span> * A component can receive events of interest by doing the following.<a name="line.52"></a> |
| <span class="sourceLineNo">053</span> * <ol><a name="line.53"></a> |
| <span class="sourceLineNo">054</span> * <li>For each type of event you wish to consume, create a public method that accepts a single event argument.<a name="line.54"></a> |
| <span class="sourceLineNo">055</span> * The method argument type indicates the type of event to receive.</li><a name="line.55"></a> |
| <span class="sourceLineNo">056</span> * <li>Annotate each of these public methods with the {@link org.apache.shiro.event.Subscribe Subscribe} annotation.</li><a name="line.56"></a> |
| <span class="sourceLineNo">057</span> * <li>Register the component with the event bus:<a name="line.57"></a> |
| <span class="sourceLineNo">058</span> * <pre><a name="line.58"></a> |
| <span class="sourceLineNo">059</span> * eventBus.register(myComponent);<a name="line.59"></a> |
| <span class="sourceLineNo">060</span> * </pre><a name="line.60"></a> |
| <span class="sourceLineNo">061</span> * </li><a name="line.61"></a> |
| <span class="sourceLineNo">062</span> * </ol><a name="line.62"></a> |
| <span class="sourceLineNo">063</span> * After registering the component, when when an event of a respective type is published, the component's<a name="line.63"></a> |
| <span class="sourceLineNo">064</span> * {@code Subscribe}-annotated method(s) will be invoked as expected.<a name="line.64"></a> |
| <span class="sourceLineNo">065</span> *<a name="line.65"></a> |
| <span class="sourceLineNo">066</span> * This design (and its constituent helper components) was largely influenced by<a name="line.66"></a> |
| <span class="sourceLineNo">067</span> * Guava's <a href="http://docs.guava-libraries.googlecode.com/git/javadoc/com/google/common/eventbus/EventBus.html">EventBus</a><a name="line.67"></a> |
| <span class="sourceLineNo">068</span> * concept, although no code was shared/imported (even though Guava is Apache 2.0 licensed and could have<a name="line.68"></a> |
| <span class="sourceLineNo">069</span> * been used).<a name="line.69"></a> |
| <span class="sourceLineNo">070</span> *<a name="line.70"></a> |
| <span class="sourceLineNo">071</span> * This implementation is thread-safe and may be used concurrently.<a name="line.71"></a> |
| <span class="sourceLineNo">072</span> *<a name="line.72"></a> |
| <span class="sourceLineNo">073</span> * @since 1.3<a name="line.73"></a> |
| <span class="sourceLineNo">074</span> */<a name="line.74"></a> |
| <span class="sourceLineNo">075</span>public class DefaultEventBus implements EventBus {<a name="line.75"></a> |
| <span class="sourceLineNo">076</span><a name="line.76"></a> |
| <span class="sourceLineNo">077</span> private static final Logger log = LoggerFactory.getLogger(DefaultEventBus.class);<a name="line.77"></a> |
| <span class="sourceLineNo">078</span><a name="line.78"></a> |
| <span class="sourceLineNo">079</span> private static final String EVENT_LISTENER_ERROR_MSG = "Event listener processing failed. Listeners should " +<a name="line.79"></a> |
| <span class="sourceLineNo">080</span> "generally handle exceptions directly and not propagate to the event bus.";<a name="line.80"></a> |
| <span class="sourceLineNo">081</span><a name="line.81"></a> |
| <span class="sourceLineNo">082</span> //this is stateless, we can retain a static final reference:<a name="line.82"></a> |
| <span class="sourceLineNo">083</span> private static final EventListenerComparator EVENT_LISTENER_COMPARATOR = new EventListenerComparator();<a name="line.83"></a> |
| <span class="sourceLineNo">084</span><a name="line.84"></a> |
| <span class="sourceLineNo">085</span> private EventListenerResolver eventListenerResolver;<a name="line.85"></a> |
| <span class="sourceLineNo">086</span><a name="line.86"></a> |
| <span class="sourceLineNo">087</span> //We want to preserve registration order to deliver events to objects in the order that they are registered<a name="line.87"></a> |
| <span class="sourceLineNo">088</span> //with the event bus. This has the nice effect that any Shiro system-level components that are registered first<a name="line.88"></a> |
| <span class="sourceLineNo">089</span> //(likely to happen upon startup) have precedence over those registered by end-user components later.<a name="line.89"></a> |
| <span class="sourceLineNo">090</span> //<a name="line.90"></a> |
| <span class="sourceLineNo">091</span> //One might think that this could have been done by just using a ConcurrentSkipListMap (which is available only on<a name="line.91"></a> |
| <span class="sourceLineNo">092</span> //JDK 6 or later). However, this approach requires the implementation of a Comparator to sort elements, and this<a name="line.92"></a> |
| <span class="sourceLineNo">093</span> //surfaces a problem: for any given random event listener, there isn't any guaranteed property to exist that can be<a name="line.93"></a> |
| <span class="sourceLineNo">094</span> //inspected to determine order of registration, since registration order is an artifact of this EventBus<a name="line.94"></a> |
| <span class="sourceLineNo">095</span> //implementation, not the listeners themselves.<a name="line.95"></a> |
| <span class="sourceLineNo">096</span> //<a name="line.96"></a> |
| <span class="sourceLineNo">097</span> //Therefore, we use a simple concurrent lock to wrap a LinkedHashMap - the LinkedHashMap retains insertion order<a name="line.97"></a> |
| <span class="sourceLineNo">098</span> //and the lock provides thread-safety in probably a much simpler mechanism than attempting to write a<a name="line.98"></a> |
| <span class="sourceLineNo">099</span> //EventBus-specific Comparator. This technique is also likely to be faster than a ConcurrentSkipListMap, which<a name="line.99"></a> |
| <span class="sourceLineNo">100</span> //is about 3-5 times slower than a standard ConcurrentMap.<a name="line.100"></a> |
| <span class="sourceLineNo">101</span> private final Map<Object, Subscription> registry;<a name="line.101"></a> |
| <span class="sourceLineNo">102</span> private final Lock registryReadLock;<a name="line.102"></a> |
| <span class="sourceLineNo">103</span> private final Lock registryWriteLock;<a name="line.103"></a> |
| <span class="sourceLineNo">104</span><a name="line.104"></a> |
| <span class="sourceLineNo">105</span> public DefaultEventBus() {<a name="line.105"></a> |
| <span class="sourceLineNo">106</span> this.registry = new LinkedHashMap<Object, Subscription>(); //not thread safe, so we need locks:<a name="line.106"></a> |
| <span class="sourceLineNo">107</span> ReentrantReadWriteLock rwl = new ReentrantReadWriteLock();<a name="line.107"></a> |
| <span class="sourceLineNo">108</span> this.registryReadLock = rwl.readLock();<a name="line.108"></a> |
| <span class="sourceLineNo">109</span> this.registryWriteLock = rwl.writeLock();<a name="line.109"></a> |
| <span class="sourceLineNo">110</span> this.eventListenerResolver = new AnnotationEventListenerResolver();<a name="line.110"></a> |
| <span class="sourceLineNo">111</span> }<a name="line.111"></a> |
| <span class="sourceLineNo">112</span><a name="line.112"></a> |
| <span class="sourceLineNo">113</span> public EventListenerResolver getEventListenerResolver() {<a name="line.113"></a> |
| <span class="sourceLineNo">114</span> return eventListenerResolver;<a name="line.114"></a> |
| <span class="sourceLineNo">115</span> }<a name="line.115"></a> |
| <span class="sourceLineNo">116</span><a name="line.116"></a> |
| <span class="sourceLineNo">117</span> public void setEventListenerResolver(EventListenerResolver eventListenerResolver) {<a name="line.117"></a> |
| <span class="sourceLineNo">118</span> this.eventListenerResolver = eventListenerResolver;<a name="line.118"></a> |
| <span class="sourceLineNo">119</span> }<a name="line.119"></a> |
| <span class="sourceLineNo">120</span><a name="line.120"></a> |
| <span class="sourceLineNo">121</span> public void publish(Object event) {<a name="line.121"></a> |
| <span class="sourceLineNo">122</span> if (event == null) {<a name="line.122"></a> |
| <span class="sourceLineNo">123</span> log.info("Received null event for publishing. Ignoring and returning.");<a name="line.123"></a> |
| <span class="sourceLineNo">124</span> return;<a name="line.124"></a> |
| <span class="sourceLineNo">125</span> }<a name="line.125"></a> |
| <span class="sourceLineNo">126</span><a name="line.126"></a> |
| <span class="sourceLineNo">127</span> registryReadLock.lock();<a name="line.127"></a> |
| <span class="sourceLineNo">128</span> try {<a name="line.128"></a> |
| <span class="sourceLineNo">129</span> //performing the entire iteration within the lock will be a slow operation if the registry has a lot of<a name="line.129"></a> |
| <span class="sourceLineNo">130</span> //contention. However, it is expected that the very large majority of cases the registry will be<a name="line.130"></a> |
| <span class="sourceLineNo">131</span> //read-mostly with very little writes (registrations or removals) occurring during a typical application<a name="line.131"></a> |
| <span class="sourceLineNo">132</span> //lifetime.<a name="line.132"></a> |
| <span class="sourceLineNo">133</span> //<a name="line.133"></a> |
| <span class="sourceLineNo">134</span> //The alternative would be to copy the registry.values() collection to a new LinkedHashSet within the lock<a name="line.134"></a> |
| <span class="sourceLineNo">135</span> //only and the iteration on this new collection could be outside the lock. This has the performance penalty<a name="line.135"></a> |
| <span class="sourceLineNo">136</span> //however of always creating a new collection every time an event is published, which could be more<a name="line.136"></a> |
| <span class="sourceLineNo">137</span> //costly for the majority of applications, especially if the number of listeners is large.<a name="line.137"></a> |
| <span class="sourceLineNo">138</span> //<a name="line.138"></a> |
| <span class="sourceLineNo">139</span> //Finally, the read lock is re-entrant, so multiple publish calls will be<a name="line.139"></a> |
| <span class="sourceLineNo">140</span> //concurrent without penalty since publishing is a read-only operation on the registry.<a name="line.140"></a> |
| <span class="sourceLineNo">141</span><a name="line.141"></a> |
| <span class="sourceLineNo">142</span> for (Subscription subscription : this.registry.values()) {<a name="line.142"></a> |
| <span class="sourceLineNo">143</span> subscription.onEvent(event);<a name="line.143"></a> |
| <span class="sourceLineNo">144</span> }<a name="line.144"></a> |
| <span class="sourceLineNo">145</span> } finally {<a name="line.145"></a> |
| <span class="sourceLineNo">146</span> registryReadLock.unlock();<a name="line.146"></a> |
| <span class="sourceLineNo">147</span> }<a name="line.147"></a> |
| <span class="sourceLineNo">148</span> }<a name="line.148"></a> |
| <span class="sourceLineNo">149</span><a name="line.149"></a> |
| <span class="sourceLineNo">150</span> public void register(Object instance) {<a name="line.150"></a> |
| <span class="sourceLineNo">151</span> if (instance == null) {<a name="line.151"></a> |
| <span class="sourceLineNo">152</span> log.info("Received null instance for event listener registration. Ignoring registration request.");<a name="line.152"></a> |
| <span class="sourceLineNo">153</span> return;<a name="line.153"></a> |
| <span class="sourceLineNo">154</span> }<a name="line.154"></a> |
| <span class="sourceLineNo">155</span><a name="line.155"></a> |
| <span class="sourceLineNo">156</span> unregister(instance);<a name="line.156"></a> |
| <span class="sourceLineNo">157</span><a name="line.157"></a> |
| <span class="sourceLineNo">158</span> List<EventListener> listeners = getEventListenerResolver().getEventListeners(instance);<a name="line.158"></a> |
| <span class="sourceLineNo">159</span><a name="line.159"></a> |
| <span class="sourceLineNo">160</span> if (listeners == null || listeners.isEmpty()) {<a name="line.160"></a> |
| <span class="sourceLineNo">161</span> log.warn("Unable to resolve event listeners for subscriber instance [{}]. Ignoring registration request.",<a name="line.161"></a> |
| <span class="sourceLineNo">162</span> instance);<a name="line.162"></a> |
| <span class="sourceLineNo">163</span> return;<a name="line.163"></a> |
| <span class="sourceLineNo">164</span> }<a name="line.164"></a> |
| <span class="sourceLineNo">165</span><a name="line.165"></a> |
| <span class="sourceLineNo">166</span> Subscription subscription = new Subscription(listeners);<a name="line.166"></a> |
| <span class="sourceLineNo">167</span><a name="line.167"></a> |
| <span class="sourceLineNo">168</span> this.registryWriteLock.lock();<a name="line.168"></a> |
| <span class="sourceLineNo">169</span> try {<a name="line.169"></a> |
| <span class="sourceLineNo">170</span> this.registry.put(instance, subscription);<a name="line.170"></a> |
| <span class="sourceLineNo">171</span> } finally {<a name="line.171"></a> |
| <span class="sourceLineNo">172</span> this.registryWriteLock.unlock();<a name="line.172"></a> |
| <span class="sourceLineNo">173</span> }<a name="line.173"></a> |
| <span class="sourceLineNo">174</span> }<a name="line.174"></a> |
| <span class="sourceLineNo">175</span><a name="line.175"></a> |
| <span class="sourceLineNo">176</span> public void unregister(Object instance) {<a name="line.176"></a> |
| <span class="sourceLineNo">177</span> if (instance == null) {<a name="line.177"></a> |
| <span class="sourceLineNo">178</span> return;<a name="line.178"></a> |
| <span class="sourceLineNo">179</span> }<a name="line.179"></a> |
| <span class="sourceLineNo">180</span> this.registryWriteLock.lock();<a name="line.180"></a> |
| <span class="sourceLineNo">181</span> try {<a name="line.181"></a> |
| <span class="sourceLineNo">182</span> this.registry.remove(instance);<a name="line.182"></a> |
| <span class="sourceLineNo">183</span> } finally {<a name="line.183"></a> |
| <span class="sourceLineNo">184</span> this.registryWriteLock.unlock();<a name="line.184"></a> |
| <span class="sourceLineNo">185</span> }<a name="line.185"></a> |
| <span class="sourceLineNo">186</span> }<a name="line.186"></a> |
| <span class="sourceLineNo">187</span><a name="line.187"></a> |
| <span class="sourceLineNo">188</span> private class Subscription {<a name="line.188"></a> |
| <span class="sourceLineNo">189</span><a name="line.189"></a> |
| <span class="sourceLineNo">190</span> private final List<EventListener> listeners;<a name="line.190"></a> |
| <span class="sourceLineNo">191</span><a name="line.191"></a> |
| <span class="sourceLineNo">192</span> public Subscription(List<EventListener> listeners) {<a name="line.192"></a> |
| <span class="sourceLineNo">193</span> List<EventListener> toSort = new ArrayList<EventListener>(listeners);<a name="line.193"></a> |
| <span class="sourceLineNo">194</span> Collections.sort(toSort, EVENT_LISTENER_COMPARATOR);<a name="line.194"></a> |
| <span class="sourceLineNo">195</span> this.listeners = toSort;<a name="line.195"></a> |
| <span class="sourceLineNo">196</span> }<a name="line.196"></a> |
| <span class="sourceLineNo">197</span><a name="line.197"></a> |
| <span class="sourceLineNo">198</span> public void onEvent(Object event) {<a name="line.198"></a> |
| <span class="sourceLineNo">199</span><a name="line.199"></a> |
| <span class="sourceLineNo">200</span> Set<Object> delivered = new HashSet<Object>();<a name="line.200"></a> |
| <span class="sourceLineNo">201</span><a name="line.201"></a> |
| <span class="sourceLineNo">202</span> for (EventListener listener : this.listeners) {<a name="line.202"></a> |
| <span class="sourceLineNo">203</span> Object target = listener;<a name="line.203"></a> |
| <span class="sourceLineNo">204</span> if (listener instanceof SingleArgumentMethodEventListener) {<a name="line.204"></a> |
| <span class="sourceLineNo">205</span> SingleArgumentMethodEventListener singleArgListener = (SingleArgumentMethodEventListener) listener;<a name="line.205"></a> |
| <span class="sourceLineNo">206</span> target = singleArgListener.getTarget();<a name="line.206"></a> |
| <span class="sourceLineNo">207</span> }<a name="line.207"></a> |
| <span class="sourceLineNo">208</span> if (listener.accepts(event) && !delivered.contains(target)) {<a name="line.208"></a> |
| <span class="sourceLineNo">209</span> try {<a name="line.209"></a> |
| <span class="sourceLineNo">210</span> listener.onEvent(event);<a name="line.210"></a> |
| <span class="sourceLineNo">211</span> } catch (Throwable t) {<a name="line.211"></a> |
| <span class="sourceLineNo">212</span> log.warn(EVENT_LISTENER_ERROR_MSG, t);<a name="line.212"></a> |
| <span class="sourceLineNo">213</span> }<a name="line.213"></a> |
| <span class="sourceLineNo">214</span> delivered.add(target);<a name="line.214"></a> |
| <span class="sourceLineNo">215</span> }<a name="line.215"></a> |
| <span class="sourceLineNo">216</span> }<a name="line.216"></a> |
| <span class="sourceLineNo">217</span> }<a name="line.217"></a> |
| <span class="sourceLineNo">218</span> }<a name="line.218"></a> |
| <span class="sourceLineNo">219</span>}<a name="line.219"></a> |
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